![]() Our Heat Pumps Have Been Very Good This Year All over California, I hear skepticism about switching from gas to heat pumps.
So, I decided to do it myself. 2024 was the first full year when our 3-bedroom 2,000 square foot home in Long Beach was All-Electric. Let’s see what our utility usage says about electrification. ![]() While on gas, our house used 5,750 kWh of electricity and 250 therms of gas with the most efficient gas systems money could buy: a 95% efficient tankless gas water heater and a 95% efficient 2-stage gas furnace. As an energy consultant, I knew that heat pumps were more efficient than gas appliances, with COPs above 3.0 (300% efficiency). My energy modeling software predicted the energy use for heat pumps in my climate zone, but you never really know until you try it and measure the results. With heat pumps replacing the last two gas appliances in my home, we used 6,415 kWh of electricity and no gas in 2024. That’s an increase of only 685 kWh (about 12%). We even had the utility come and remove the gas meter completely, which eliminated our gas bill. How could we switch all of our space and water heating from gas to electricity and see such a small increase in electricity usage? ![]() Heat Pumps Really Are That Efficient
With gas, I wasn’t able to determine the exact usage attributable to space heating versus water heating. Assuming that my hot water usage stayed relatively constant each month, looking at my summer gas usage gave me a good estimate of my monthly water heating usage, with the increase in monthly gas use during the winter attributable to space heating. So I estimated my gas usage to be 50 therms for water heating and 200 therms for space heating per year. In 2023, we installed a Rheem 50-gallon heat pump water heater to replace the tankless gas water heater. It’s installed in a well-ventilated closet on the side yard, so it pulls heat from the outside air. We chose a 120-volt unit, since there was already a 120-volt outlet in place from the gas tankless system. Note that most HPWH units installed in California are the 240-volt variety that come with backup electric resistance elements for really cold days or when the heat pump can’t keep up with the hot water demand. Installing a 240-volt unit would have required bringing out an electrician to run a new circuit. We calculated that 50 gallons would be enough hot water to supply up to 4 consecutive showers, since we have efficient shower heads (1.8 gallons per minute) and our climate never falls below the heat pump cutoff temperature (about 38 degrees). That has proven true. The data from my home energy monitoring system shows that in 2024, our family used 432 kWh to heat water, averaging 1.2 kWh per day or 36 kWh per month. Assuming an average electric rate of $0.35/kWh, I estimate we are paying ~$12 a month to run the heat pump water heater. In comparison, the 4-5 therms of gas we used with the tankless water heater cost us ~$10 per month (at ~$2.00-$2.50/therm), so let’s call water usage a push on utility costs. Plus, I can’t tell you the satisfaction taking a shower with hot water you know was produced without burning gas – a cleaner feeling all around! By scheduling the heat pump to avoid peak hours (4-9 pm) and using hot water during the day when solar panels are active, your showers can feel even cleaner. “Heat pump water heaters don’t have the same capacity as gas models”, true or false? Answer: False-ish. A 50-gallon tank water heater has the same capacity, whether it’s heat pump, electric, or gas. But the statement is true if we’re talking about “heat rate” – the speed at which the water heater can replenish hot water as it’s used. We’ve never run out of hot water, though for most of the year, it’s just my wife and I using it. The holidays gave us a chance to put the water heater to the test. The chart below shows daily electricity usage on our water heating circuit in December, 2024. Note that there are some other receptacles drawing power on this circuit, but it’s mostly water heating. The beginning of the month shows usage with just my wife and me at home, down around 1 kWh per day. Then our two daughters came home and we were making hot water for 4-6 showers a day instead of two, so our water heating usage went up to 3 kWh per day some days. That’s the holidays for you. I made it a point to shower last on the day when we needed six showers and that was the first time I noticed our hot water had cooled a bit. It was still a good hot shower, but our 50 gallon tank ran low at that point. That made me feel more confident recommending heat pump water heaters to my clients. Install a 240V model with back-up resistance elements and you’ll be better off than we are with our 120V unit with no back-up. ![]() 2. Space Heating My energy modeling runs over the years had shown there to be significant energy and utility bill savings possible by switching from gas furnaces to minisplit heat pumps. But the modeling world and the real world are two different things. Would my utility bills go up heating our home with an electric heat pump? Do they even work, as the skeptics have been asking? There was only one way to find out… We had a ducted gas furnace in the attic and an air conditioner, often called a split system because the furnace was used for heating and the air conditioner for cooling. The simplest change-out for a ducted split system like this is to replace the furnace and air handler with a heat pump, keeping the existing ductwork, supply, and return registers. We installed a Mitsubishi “multi-position air handler” with similar dimensions to the old unit. This connected to a new outdoor unit (see earlier photo captioned “My Heat Pumps Have Been Very Good This Year”) with refrigerant lines. The 240-volt, 30 amp circuit that served the old air conditioner now serves both the new indoor and outdoor units, freeing up the 120-volt circuit previously used by the old air handler in the attic, reducing panel space usage. The old system used energy in three different ways: gas for the furnace, electricity for the air conditioner, and electricity for the air handler. My energy monitoring system counted 1,434 kWh and our gas bill showed 200 therms to run all three pieces of the HVAC system. The air conditioner was about 1,000 kWh in summer and the air handler was about 430 kWh running all year for heating and cooling. The heat pump uses a single circuit, but how much higher would its energy use be handling heating and cooling year-round, compared to the 1,434 kWh with the old system not providing heating — Double? Triple? Based on my energy models, I knewthat heating use in Long Beach is higher than people think, but I expected HVAC electricity use to double, even with the efficient variable capacity inverter driven heat pump we installed. These are able to purr along at low-load throughout much of the year, which is a big part of where they get their high efficiency from. The answer at the end of the year shocked me – the electricity usage for HVAC went up only 31%, and the old system was efficient, how was this possible? Was the weather different in 2024 from the year I collected the data on the old gas furnace split system? Some digging was in order… 3. The Digging Confirms that Minisplits are Very Efficient Question #1: “Was the weather different and does that explain why electricity usage only went up 31% with the heat pump?” Answer: Nope. Daily average temperatures are shown in the chart below; they were very similar for the two data collection periods. The mean was 1.2 degrees cooler in 2023 with the gas furnace. Measured in total heating and cooling degree-days, 2023 was 2,525 and 2024 was 2,252. The weather certainly doesn’t explain why the heat pump was able to do the same job as the old gas system without using much more electricity. As a side note, we also installed a ductless minisplit heat pump system in our all-electric ADU, which we completed in 2023. It used only 544 kWh to heat and cool the ADU last year, which is 576 square foot and 1 bedroom. So both our heat pumps have been very good this year. Question #2: “Was the heat pump’s higher efficiency the reason? Was it more efficient at heating or cooling?” Answer: Yes, YES, and Yes. To evaluate this, we looked at cooling energy use per cooling degree-day. This accounts for weather variations and allows us to measure efficiency across different conditions. Heat pump cooling electricity usage per cooling degree-day: 1.00 Old air conditioner cooling electricity usage per cooling degree-day: 1.47 The old air conditioner had two stages, one for mild days and the second one kicked in when needed for hotter days. It had a 16 SEER rating, better than code minimum. However I was shocked to learn it used 47% more electricity to cool our house than the heat pump! In fact, 2024 had 20% more cooling degree-days than 2023, meaning that equivalent weather years would have shown the heat pump outperforming the air conditioner by well over 50%, maybe even 60%. Heating is tougher to compare since the furnace used gas and the heat pump uses electricity. However. analysis of the old system shows it used 200 therms of gas plus 242 kWh of electricity for air movement during the heating season. If we convert the 200 therms to theoretical kWh using a factor of 29.3 kWh per therm, we can compare the heating energy use of both systems. The new heat pump used only 911 kWh of electricity in heating season. Heat pump heating electricity usage per heating degree-day: 0.71 Old furnace heating energy usage per heating degree-day: 3.57 This comparison highlights the heat pump’s efficiency and the real-world meaning of its 300% efficiency. The furnace was using 5X more energy to heat our house than the heat pump! Perhaps that 300% efficiency figure was an underestimate. The year we measured the gas furnace had 34% more heating degree-days than the year with the heat pump. But we’ve accounted for that in the metrics above. Perhaps our heat pump would have used ~1,200 kWh in heating mode if it were to go through another year like 2023. Even so, we would still be very satisfied with that, especially compared to the old gas system. ![]() 4. What About Cooking and Laundry? Cooking electricity usage, 2024: 436 kWh Washer & Dryer electricity usage, 2024: 550 kWh We have a 4-circle (can’t call them burners) induction cooktop and electric oven for cooking. We cook most nights, using ~500 kWh per year. In late 2023, we added a countertop air fryer, which we use occasionally instead of the oven or cooktop, reducing our 2024 cooking usage by ~125 kWh. At an average cost of $0.40/kWh, 500 kWh costs about $200 per year for cooking electricity usage, not bad. Note that I used a higher per-kWh rate for cooking, as it’s typically done in the evening when electricity rates are highest and our solar panels are no longer producing. We have a stacked Miele washer and heat pump clothes dryer for laundry. They used about the same amount of electricity as our cooking: 484 kWh in 2023 and 550 kWh in 2024. When we had a gas dryer, electricity usage was 258 kWh, so the heat pump dryer added about 230 kWh per year. For an electric resistance dryer, it would have been 3X that amount. The difference in utility costs for laundry is that we can run it during the day on solar power from our roof. I bet that half of our laundry usage costs us nothing, thanks to solar power. 5. Actual Utility Bills You won’t believe this, but our utility bills were much lower all-electric. I’ll bottom-line it for you. 2024 utility bills (all-electric): $1,400*** 2023 utility bills (mixed fuel): $763 electric + $637 gas = $1,400 *** EV charging usage was 1,055 kWh higher in 2024 than 2023 If you exclude the extra ~1,000 kWh used to “fuel” our EVs, our 2024 all-electric utility bills were much lower than our utility bills with gas, probably about $400 lower per year! I say “probably about $400 lower” because calculating utility bills in California is really complicated these days. There are multiple layers of complexity:
We paid $1,400 in electricity bills this year, with our home converted to all-electric and a 4.4 kW solar system (now 9 years old) on the roof. For the first 4 years our total annual electric bill was $0, but since then we’ve added two electric vehicles which we charge at home, and we’ve faced rate increases in California. In addition to our home’s operating costs, the $1400 annual electricity bill also covered almost all of our transportation costs. We used 2,800 kWh of electricity to “fuel” our two EVs – a 2019 Chevy Bolt and a 2023 Kia Niro. That’s 11,200 miles worth of travel at 4 miles per kWh, covered by our $1,400 electric bill. We also charged occasionally at public stations during road trips, and probably drove 15,000 miles in total this year. To have a single bill cover the cost of operating your house and your cars is really convenient. I estimate we would have spent about $1,500 on gas for 11,200 miles of travel this year (30 mpg @ $4.00 per gallon), so our utility bills of $1,400 mostly covers transportation. Our house operates for next to nothing, thanks to efficient heat pumps, solar panels, and good building envelope. And we no longer have the gas bill coming to our email inbox, which cost us $637 in 2023, the last year we used gas. 6. Key Takeaways My family is very satisfied with our switch from gas to electric. The house operates trouble-free and keeps us comfortable. Here’s the executive summary of results:
![]() APPENDIX: For Energy Modeling Enthusiasts My business is energy modeling. We use computer models of buildings to optimize their energy efficiency and verify compliance with the California Energy Code, also known as Title 24. But we rarely get to compare actual energy usage to modeled. I modeled my actual house with every feature from insulation to windows and I modeled it before we electrified and after. Here's what I found. The modeling software (Energy Pro v9 for 2022 energy code compliance) overestimated energy use in the mixed fuel home by 18% on electricity and 26% on gas. The overestimate was much larger in the all-electric home: the modeling software estimated energy use would be 50% higher than it actually was! The table below shows the actual usage versus the modeled usage by end use. The biggest over-estimates by the model were in the all-electric heating (+163%), water heating (+102%), and cooling (+49%). In the mixed fuel model, the software also over-estimated water heating gas usage (+112%), but other estimates were much closer. Judging by our family’s actual usage, the modeling software gives over-estimates of energy use and larger over-estimates for all-electric homes. This suggests that the savings for electrification are larger than the software predicts, which makes electrification a more attractive proposition than we had assumed based on the software’s predictions. This is one home with one family and should not be assumed to be consistent across California, but it is one useful data point to try to understand electrification's benefits.
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As an emerging professional stepping into the world of energy consulting, I’ve quickly discovered how rich and vital this field is, especially in California. I’m excited to share my experiences and insights so far, 1.5 years in, for anyone considering this path or curious about the building energy efficiency sector. A Welcoming Community From day one, I felt embraced by a passionate and close-knit community dedicated to the California Energy Code. The support from seasoned professionals has been incredible. They encouraged me to stay in this important work, which has made the transition into this field not just smooth, but truly inspiring. I remember thinking “these are my people!” – the camaraderie here is palpable and it motivates me every day. The Importance of Our Work Did you know that California’s buildings significantly contribute to the state’s greenhouse gas emissions, accounting for about a quarter of the total? This reality means that decarbonizing our buildings is a monumental step towards achieving California’s clean energy goals. Every project I engage in feels like a step toward a cleaner future, and it’s empowering to know I’m actively participating in the fight against climate change. Continuous Learning and Growth Attending the annual CABEC, California Association of Building Energy Consultants, conference has been a highlight of my journey. This event brings together leaders from the California Energy Commission, the California Public Utilities Commission, local jurisdictions, and other key stakeholders. It’s a fantastic opportunity for meaningful discussions about research findings and best practices. The exchange of ideas is not just enriching; it’s essential for staying current in this fast-paced field. With new technologies and code updates emerging regularly, adaptability is crucial in this field. Resources at our Fingertips
As an environmental policy graduate exploring the industry was overwhelming at first because of all the possible directions I could take. But what really excited me about this industry is the abundance of resources available that were perfect for learning. Organizations like 3CREN, SCE, and Energy Code Ace provide a wealth of educational tools whether it’s fact sheets, webinars or newsletters. Many experts in this field come from completely unrelated backgrounds. I’ve met people with degrees in music, experience in the restaurant industry, and even an elementary school teacher! The wealth of resources makes it easy for newcomers to jump into the field and for everyone—from homeowners to contractors—to engage and contribute. Flexibility The energy consulting sector is particularly well-suited for remote work, providing the flexibility that enhances work-life balance and boosts productivity. I manage my own schedule and create a workspace that fosters my best performance. The autonomy I enjoy not only allows me to manage my time effectively but also leads to a more satisfying and fulfilling work experience overall. Finding Balance As an energy consultant, I quickly learned that this job is all about finding the right balance. There are many factors to juggle -- cost effectiveness, client needs, architectural requirements, and local climate conditions. Each project presents its own challenges, like an all-glass building in the Mojave Desert or circular/triangular shaped homes, which keeps things interesting. Raising Awareness Despite its importance, the building energy efficiency sector isn’t well-known among the general public. As California pushes toward its clean energy goals, it’s crucial to spread awareness about this industry and its role in fighting climate change. We need a new generation of professionals to step up and continue this essential work, ensuring that energy efficient buildings get the attention they deserve. Diverse Career Paths Lastly, The CABEC Conference opened my eyes to the various roles within the building energy efficiency industry. Whether you’re interested in consulting, engineering, or policymaking, there’s a niche for you. As I continue my journey in energy consulting, I’m grateful for the opportunities and challenges that lie ahead. With a supportive community, a wealth of resources, and a chance to make a real impact, this field is an exciting place to build a career. If you’re considering entering the energy sector or are unsure of your direction, I wholeheartedly encourage you to explore the building energy efficiency field. ![]() NBC Nightly News got it wrong about California’s solar situation with their July 8 segment titled “California’s Unexpected Energy Challenge: Too Much Solar.” Correspondent Liz Kreutz used these provocative but completely inaccurate visuals and spoke of California “losing” or “wasting” energy. How our national media could get this so wrong was shocking – so much so that I was motivated to write this piece. Unexpected? No, the challenge of managing supply and demand of electricity with increasing renewables is a known issue called “The Duck Curve” that California has devoted extensive research to. Too Much Solar? No, we’re going to need more solar, more wind, and more batteries to store it as we move toward an emission free electric grid by 2045, as required by the SB-100 bill passed in 2018 by the California legislature and signed by the Governor. ![]() At one point, correspondent Liz Kreutz asks Eliot Mainzer, CEO of CAISO, California’s main grid operator, if curtailment means “throwing solar power away.” He disagrees, explaining that curtailment involves sending dispatch instructions to reduce generation. But Mr. Mainzer missed the chance to deliver a full-throated defense of clean energy. Curtailment is not waste; it’s an inescapable truth of generating electricity from renewables. There are times when we have more power than we need and times when we need to turn to other sources like battery storage and gas power plants. Saying that we are “throwing solar power away” is like saying buffet restaurants need to be banned because they sometimes make more food than customers want to eat. The point that the national news missed is that, even factoring in the times when solar power plants make electricity we can’t use, solar power plants are less expensive ways of growing our electric grid than all other options. Growing our grid is what we’re going to be doing for the next few decades to supply EV charging and all-electric buildings with cleaner and cleaner power. When we pair solar generating facilities with battery storage, we have a more cost-effective source of new electricity than building new gas power plants, and solar plus battery is just as reliable! Recent studies by U.C. Berkeley, Princeton, and the California Energy Commission show that our grid CAN provide reliable electricity using 90% or more clean emission-free generation sources like solar, wind, and batteries. And we can do it without increasing utility costs while realizing significant public health benefits from reducing fossil fuel-related pollution. While we are already at about 60% clean energy, we still have a lot of work left to do. This is going to be the defining challenge of our generation – transitioning our buildings, vehicles, and electricity grid of fossil fuels to renewable and clean sources including nuclear and hydropower. It’s going to take all of us pulling together in the same direction to be successful on this huge challenge, so misinformation like this story is unhelpful; this is why I felt the need to correct it.
![]() In the homes we grew up in, we all happily ran our homes and businesses on tank water heaters. We found room for them in interior and exterior closets and the corner of the garage. But then came tankless water heaters and their promise of never-ending hot water. You could bolt them to the wall too and take up no floor area. The 2013 California energy code gave us such a big compliance credit for putting a gas tankless water heater in our designs that high-performance walls and -attics were the standard but completely avoidable. Ever notice that tankless water heater manufacturers have Japanese names? Rinnai, Takagi, Noritz… That’s because tankless water heaters were created in Japan to solve a very Japanese problem – no space for a tank of water in dense city apartments. Once Americans saw them, they had to have them too; we suddenly acquired a new-found need for unlimited hot water. They were marketed smartly as energy savers [look, there’s no wasted energy keeping that tank full of water hot!], but at 200,000 btu/hr, they are like taking a machine gun duck hunting – overkill. The past few years in California, gas tankless water heaters have been the standard in new homes and remodels. Enter climate change and the need to reduce Greenhouse Gas (GHG) emissions. Our modeling software proves that HWPHs have 80% lower GHG emissions and 50% lower energy use than gas tankless.[1] This is the single biggest thing you can do to bring down overall home GHG emissions. We now realize that heating our homes and our water with gas is a luxury we can no longer afford. California has appropriately realized that electric heat pump water heaters are the right system for almost every project – efficient, quiet, and more than capable of supplying all the hot water a family might need. There’s just one catch – they are tank water heaters, and require a 3’ square footprint. [1] Modeling based on new code-compliant 2-story 4 bedroom home in Inland Empire Southern California (CZ10) on 2022 CBECC-RES software comparing typical efficiency gas tankless (uef 0.81) and typical efficiency HPWH (3.5 COP) in garage. So how do we transition the California market from gas tankless water heaters to heat pump water heaters, now that we are addicted to the idea that we need never-ending hot water? It starts with realizing HPWHs are a whole lot more efficient than the old tank water heaters we grew up with (the tanks are so well insulated they lose ~4 degrees over the course of a day) and we can always find a closet or corner of the garage to put them in. Next, we need to provide training to the trades, builders, and architects on how to install them without problems. In single family homes, they can go in the corner of the attached garage or in a closet with a louvered door. In multifamily buildings, each unit can get one in a closet or they can be piped together to serve as a central system. New tools like Ecosizer are helping design such systems.
The time is now, because the climate crisis cannot be ignored and we can’t continue installing gas systems today when we know better and what we build today will operate that way for 10+ years. PLUS, there is incentive money in the TECH Program to encourage the gas-to-heat-pump water heating transition -- $3,100 for every Californian in PG&E, SCE, and SDG&E territories to replace their gas water heater with a HPWH. The 2022 California energy code took a few steps in the right direction to encourage this transition:
So take the money and run your house’s water heater on electricity. And take advantage of all the training offered by your utility, the water heater manufacturers, and Energy Code Ace, because heat pump water heaters are coming in hot! Are you a builder or developer who is working on a new construction project? If so, the Energy-Smart Homes All-Electric or Mixed Fuel Residential Programs could help you lower your project costs. These programs were created to support California’s energy efficiency policy goals and help mitigate climate change. Energy-Smart Homes Program At A Glance
What are the eligibility requirements? Both programs serve new single-family residences and duplexes, manufactured housing, multifamily low-rise buildings (three stories or less), and accessory dwelling units (ADUs). Participants must be customers of SDG&E, PG&E, SCE, or SoCal Gas and the builder/developer must pay the Public Purpose Program Charge. All new construction projects are required to install communicating thermostats, segregated circuits, battery storage readiness, thermostatic mixing valves, and electric vehicle (EV) charging infrastructure pre-wiring in accordance with CALGreen Building Code EV ready requirements. All new construction projects must also achieve an efficiency EDR of greater than or equal to one EDR point above standard in their Title 24 compliance for the All-Electric program and two points above standard for the Mixed Fuel program. There are no incentives for solar measures, so eligibility is determined by efficiency EDR only. To satisfy this eligibility requirement your Title 24 compliance must be completed by a CEA. If you are interested in this program and in need of a Title 24 consultant, contact us! We are CEA certified and happy to help you with the compliance process. What kinds of incentives are there? Incentive amounts differ depending on the type of project and year of completion. The incentives are paid on an escalating scale with a bonus incentive for each additional 0.01 EDR above the entry requirement. Base incentives de-escalate 10% annually based on completion year in the All-Electric program. Incentive amounts for new construction in the All-Electric program are listed below. The incentive amounts for new construction in the Mixed Fuel program are listed here: Case Study: All-Electric New Construction To see what kinds of incentives a project would be eligible for, we will look at a real, all-electric, new construction project. Our case study is a 2,000 sq ft single family home in Climate Zone 11. It has a central split heat pump, a heat pump water heater, and all-electric appliances. The project has a Title 24 compliance delta efficiency EDR of 4.1, meaning that it surpasses the required 1-point difference. Assuming this project is to be completed in 2022, it would receive $3,500 in incentives, plus $10 for each 0.1 EDR points over the required delta of 1. This means it would receive $3,500 + ($10 x [3.1/0.1]) or $3,810 total. How do I apply? Before you start the application process, make sure your project meets all the eligibility criteria. Part of that is getting your Title 24 compliance done by a CEA (like us)! Contact us and we will get back to you with a quote. Once you have determined you are eligible, you can start the application process by logging in to the participant portal (https://CAenergysmarthomes-OLA.Capturesportal.com) and setting up an account where you can submit application documents and a program participation agreement. If needed, you can also contact Energy-Smart Homes staff at [email protected] and they will assist you with your application or complete the inquiry form at www.caenergysmarthomes.com to have an Energy-Smart Homes representative follow up with you. I recently assisted the project team on a new school gymnasium building in Tipton, which is in California’s Central Valley. The project was approved and going out to trades for bids, and the plastering contractor had concerns that the building could not be built as it was drawn. The walls were made from concrete block, and in order to get the building to meet the California energy code, the energy consultant selected a continuous layer of R-9 Polyiso insulation board at 1.5” thick over the block, with plywood and stucco over that. This wall system cannot be built. There is no possible way to apply Polyiso to the concrete block, then apply plywood and stucco over the Polyiso. The problem was this … the building energy usage was modeled with this R-9 continuous insulation layer, for a wall U-factor of 0.070 with 8" and 12” thick concrete blocks. The insulation helped the building comply with the energy code by reducing energy usage to compensate for energy used elsewhere in the building. So the team building the gym could not substitute out another wall system with a higher U-factor and still meet the energy code. When we met all together to discuss the issue, the builder, architect, plasterer, and HVAC engineer were all present. We defined the problem and proposed alternative wall systems that would meet the same U-factor. Metal Z-furring was proposed to provide a mounting mechanism for the plywood and stucco over the foam. But the wall would have leaked energy through the Z-furring, and this would not meet the specification for a continuous layer of R-9 insulation. We found that R-9 between Z-furring would have produced a U-factor of 0.384, which is not even close to the U-factor used for compliance. So we turned to the ideal wall system for continuous insulation … EIFS. EIFS is an adhesively attached system, so fastening into the concrete block is not necessary, and the stucco is adhered directly to the foam board. We found that an EIFS system with R-9 or greater insulation would meet the overall U-factor used in the modeling, whether it used Polyiso at 1.5” or Graphite EPS at 2”. How did we end up with this problem? The energy code has become complex enough that energy consulting is a specialized job with an association in California to govern the industry, CABEC. But many projects ask the mechanical engineer to handle the Title 24 paperwork. What they don’t realize is that the Title 24 energy code provides for many alternatives to comply, and allows for tradeoffs between insulation, windows, mechanical systems, water heating, etc. So to ask the mechanical engineer to run the energy models is unrealistic and probably limits design options today for any project with any complexity. And that’s what happened on this project. Gymnasium buildings need ventilation for full occupancy. To accomplish this requires large fans, which use more energy than the commercial standards allow for. So these type of buildings require energy savings in other parts of the building in order to reach compliance. In this case, higher insulation values in the walls were used to save on heating and cooling to compensate for ventilation energy. This is what we do – help building designers keep energy efficiency at the table, as key design decisions are made. And we help them navigate the increasingly complex set of regulations known as Title 24 in California.
![]() In one of the first moves of its kind, the state of California has enacted energy efficiency standards for computers and monitors. If the state that is home to Silicon Valley can take this step, an other state interested in reducing energy use could be safe to follow its lead. The new standards are estimated to save $370 million a year or 3-7% overall energy use in the state. The details are that the standards will be phased in from 2018-2021, with different standards for laptops, desktops, servers, and monitors in several categories. Chief among the new requirements are idling caps on energy use when not in use. The monitor standards have a payback of 600% over 7 years, and only 14% of current monitors would comply with the new standards. Desktops have expected payback of 400% and laptops 200%. This move shows what California has learned from its drive to tamp down energy use (and energy waste) toward its goal of netzero buildings -- the more you design in energy efficiency in the building envelope and mechanical systems, the more the "plug load" takes over as the low-hanging fruit for additional energy savings. In the net-zero home we built, for instance, fully 12% of total electric usage was plug load (see chart below). And that energy is often easier to reduce than heating, cooling, and lighting, once efficient HVAC, appliances, and LED lighting have been installed inside a tight envelope. By 2020, all new California homes are required to be net-zero. There are many definitions of net-zero, but the one that counts for the California energy code is TDV net-zero.
Think of TDV as a weighted average. The modeling software used to prove compliance with the energy code weights every hour's electric usage by the cost to produce that power in your climate zone. So peak periods count FAR MORE than non-peak periods. This means that west-facing windows (which take on heat in summer during peak periods for the utilities) get penalized more heavily than north- or east-facing windows, and in most cases south-facing windows. To give you an idea of the TDV factors, the 2016 standards have TDV factors that average 20 kbtu/kwh. Some days in August and September have TDV factors as high as 500 or 600. This is how the utilities bring the reality they deal with every day of peak production loads into the equation, and it makes sense. The energy code actively discourages designs that worsen the need for peak production, which typically is the most expensive and dirty electricity production. Now that you know what TDV is, you can understand that TDV net zero is a less stringent goal than the purest definition of net-zero, which is site net-zero. In site net-zero, a boundary is drawn around the property. The sum of what goes in is less than or equal than the sum of what goes out. If you produce as many btu's of electricity with your PV panels or wind turbines or hamsters in cages as you pull off the grid during the year, you're net-zero site. By using TDV factors and applying them to the grid energy used, the calculation weighs the on-site production more heavily than the grid energy used. Why? Because grid energy has emissions associated with it and other societal costs, whereas on-site renewable energy production does not. Also, PV panels produce a lot of their energy during peak periods, and grid energy is often drawn off-peak in a net-zero home. Bear with me; I'm getting there! Our net-zero TDV house is about 65% net-zero site. That is, we produce about 65% of the energy we use by a site definition. That will be enough to qualify as a net-zero house by the 2020 California Energy Code. If you use all electricity in your home, the calculation is easy. But what if you're a "dual fuel" home, with gas and electricity? In that case, we convert the natural gas usage to equivalent btu, do the same with electricity, and do our math in btu's. The TDV energy produced by the PV panels has to more than equal the TDV energy used by the gas systems and electric systems in the house. Hope you're still with me, because I'm just now getting to the point. Most net-zero houses are more economical to build "dual fuel", because gas is the most established and efficient way to heat a home and dry clothes and heat water in most areas of the state. In our case, 60% of our annual energy use is from natural gas; we would have needed an additional 4-6 solar panels to reach net-zero all-electric than the way we did it -- dual fuel. What's this mean? Most net-zero homes will produce more electricity than they pull off the grid. Our house had a surplus of over 1,000 kwh electricity in its first year of operation. This is partially compensating for all the gas usage in the house. And our electric utility pays us poorly for these excess kwh -- about 4 cents each last year. This is what makes an electric vehicle look attractive to a net-zero dual-fuel home. They will find they have excess electric production, purchased by their local utility at very low rates, and will look for options what to do with it. They could do wasteful things with it, like adding a big freezer in the garage or running their A/C more in summer. Or they could use it to cheaply power an electric car. Whatever they have in extra production will cost them $0.01 per mile or thereabouts, as compared to about $0.10 per mile for a typical gas car. Net-zero + Dual-fuel = EV With so many variables, it’s hard to decide on an EV. Here’s what we grappled with in our decision to (Spoiler Alert) lease a 2016 Nissan Leaf:
1.Range anxiety (at 110 miles per charge, is that enough for our family?) 2.Understanding federal and state incentives 3.Degradation in battery life over time – how real is this? 4.Drive-ability 5.Room for 5 people comfortably? 6.Newer models coming out (Tesla 3 and Chevy Bolt) 7.Cost of operation vs gas vehicle 8.How do you install a charger (EVSE) in the garage? 9.How much could we use our solar panels to charge it versus off-grid power? 10.Are those HOV stickers still available in California? 11.Lease vs buy 12.Hybrid vs Pure EV And here is what we found out and decided: 1.Range anxiety is real but do-able with planning ahead At 110 miles, that’s 50 miles each way with a 10-mile cushion. Luckily stop-and-go traffic seems to help EVs, since they regenerate some energy during braking, the opposite of gas cars. So the 10-mile cushion seems fairly safe. With the ability to trickle charge at your destination, that can add 5-10 miles per hour, and that’s possible with a standard 110V outlet and the free cable that comes with the car. With a 240V Series 2 charger on the other end, you can add 20 miles per hour to your battery and really extend your range. And if you plan around a DC charger, such as most Nissan dealers have, you can go 80+ miles, get an 80% recharge in 30 minutes and head home. So for us, we have a gas car for long trips and we will use the EV for all around town and mid-range trips of 50 miles or less, 80 miles or less with ability to charge on the other end. 2.Federal and state incentives The dealers were offering $7,500 federal rebates, and $2,500 state rebates in California, although the state money was contingent of renewal of the program, so we couldn’t take that for granted. By leasing, the $7,500 was rolled into the deal, along with other dealer incentives that pushed the capital cost reduction well over $10K. We’ll hope to get the state rebate, too. The government continues to do its best to give EVs a start in the market dominated by internal combustion engines. 3.Degradation of battery life over time The research we made showed we could expect 70% battery life after 5 years or so, and that charging behavior is a key determining factor in this. Just like a cellphone battery, if you charge it often, the battery loses its ability to hold a charge faster. So we’ve been trying to run it down under 50% before recharging. But if we have a possible trip the next day, we’ll have to top it off in the garage. With a lease, this is not a large issue. 4.Drive-ability This is answered by test driving, and your local dealer would love you to do so, because they’re so convinced you’ll be hooked that you’ll probably get one. They really are a joy to drive. The big difference I noticed right away was acceleration. There is no delay between putting the pedal down and the engine responding, so it’s peppy. Acceleration on the freeway onramp is scary easy. And the Leaf handles turns and braking nicely as well. I’ve never been so excited about driving a new car as this one, and I’ve probably driven a dozen new cars over the years. 5.Room for 5 people Because they have to count their pounds like the Weight Watchers of car designers, EVs are not as roomy as their gas cousins. But I found the Leaf had plenty of room for 3 in the back seat 6. Wait for new models or pull the trigger now? We had a career change that made this decision for us. And the 3-year lease gives us a timetable to get to where the new Teslas, Chevys, and Nissans have worked out some bugs and extended range on affordable models to 200+ miles. Then our next EV can be all the car we’d ever need to go between LA and San Francisco with one stop or go to the mountains. But if I had a car with 2 years left in it, I would have run it into the ground and waited for the next generation of EVs. 7.Cost of operation This breaks down into gas vs electricity cost and maintenance and insurance cost differences, if any. Let’s assume we’re getting 3.8 miles/kwh on the Leaf (which we are). At $0.20/kwh, that’s about $0.05/mile. A comparable gas car might get 30 miles per gallon on $3/gallon gas. That’s $0.10/mile (double). Plus, maintenance should be much less for an EV, with fewer moving parts under the hood. And insurance on the Leaf was less than our other cars. So we stand to save $750/yr on gas alone at 15,000 miles/yr. 8.Chargers 101 You don’t call it a charger, first of all! The EV community seems pretty stubborn about calling them EVSE’s. So we’ll have to go with that until a TV show character gives one a cooler name. For now, I’ll call it a charger. I found some for $300, but ended up getting a Clipper Creek one for $600 that everyone swore by. I had a 30 amp RV plug at 240V already on the back of the garage, and planned to use that. But that could only handle the 24 amp charger. The 32 amp charger would make a big difference in charging speed, so I had my electrician upgrade the breaker to 40 amps and ran a new line in the garage. It is charging from nothing to full in about 5 hours. The brains of the whole charging thing is in the car. The car knows when to turn off the charger. The car can set a timer to turn on and off at a certain time to take advantage of off-peak electric rates. All you need that EVSE to do then is safely move the current. You might spend your first year’s gas savings on an EVSE and installation. 9.Using solar power to charge the car We have an excess of solar PV capacity on the roof of about 1,000 kwh/year, or 3,800 miles per year worth. The utility pays us $0.04/kwh for that power, as part of our net metering agreement, so that’s a bum deal. We might as well use it for an EV. That means the first 3,800 miles per year are at $0.01/mile. Then we start paying Tier I rates from the utility. But, even in the middle of summer in the middle of the day, when our PV panels are maxed out, they only produce 4 kw, and the charger uses 6.6 kw, so we can’t charge at full blast without help from the grid. All that comes out in the end-of-year wash, when the utility calculates what we took versus what we returned to the grid, regardless of what time of day it was. Net metering is a good deal for the consumer, who gets to use the grid whenever their panels can’t power them as a virtual battery, and just clear up their account at the end of the year, like those general store owners used to do in all the Westerns when the farmers sold their crops for the year and bought their wives and daughters fabric to make dresses. 10.HOV stickers in California We wanted one of those mud flap stickers like on those Priuses when they first started strutting their environmental superiority over our gas cars 15 years ago. But we also heard those stickers aren’t available any more. Well it seems that’s true, for hybrid EVs (check your specific model at the DMV website). But for our ZEV (zero emission vehicle), they have a shiny white HOV lane sticker available by mail for $22, once you get your registration in the mail. And until then, you can drive the carpool lane with impunity since you have no plates; just watch for the highway patrolman. 11.Lease vs buy We bought our solar panels when leasing them would have been easier, so we’re not lease lovers. But with the longer range models coming online in the next year or two, and the dealers’ willingness to take all the uncertainty and paperwork out of the federal rebate process for us, and a sub-$300/month lease on offer with a reasonable downpayment, we decided on the 15,000/mile a year lease. 12.Hybrid vs Pure EV A plug-in hybrid seems like the perfect compromise … the economy of an EV driving around town near home with the range of a regular gas car. But we just wanted to make more of a statement than that … that we can plan around limited range and charging stations to make an electric vehicle with no emissions work. And why spend an extra $2,000 or so to have a redundant engine under the hood – that’s not a no-cost compromise. My wife and I just have come to believe through our research that the natural gas plant down the street can burn gas and make electricity and get it to our house to charge our car more efficiently than the oil companies can get gasoline to the gas station by way of the refinery by way of the ship from the Middle East for my gas engine to burn. And if 30-50% of the power comes from my rooftop solar panels or solar panels in the Mojave Desert or hydropower, then I think that makes a pure EV make good sense now and, even more so, in future. In 2010, we wrote: "The updated California energy code is changing the insulation and plaster systems being used throughout the state." We said it then and we have to now say it again, and this time the impact of the 2013 California Energy Code standards will be much more significant than the last cycle. This is because the new code requires significant upgrades in the insulation of wall systems. For the past few years, residential standards for wall systems in much of the most populated areas of the State were status-quo, and commercial standards were done by measuring the effective insulation value of the entire wall system, taking into account thermal transfer through framing and windows. This overall approach to wall insulation now comes to residential construction with the start of the 2013 standards in July, 2014. This represents a paradigm shift in how exterior walls of residential structures will be built in the State Climate Zones Climate Zones played a big role in the residential wall requirements in the past edition of the energy code; not so now. All climate zones now require an overall wall U-factor of 0.065. That translates into an effective R-value of about 15, taking into account the leakage through studs called thermal bridging. To comply, many new homes will be built with continuous insulation, a method in which foam board is installed outside of the framing in a continuous sheet, with the exterior cladding installed over it. It is important to understand that tradeoffs between systems are allowed. As long as the house will use the same amount of energy as the specified designs, you can trade off insulation against windows, HVAC systems, etc. How Are Builders Complying? In order to comply with some of the stricter requirements under Title 24, continuous foam insulation (CI) is becoming more common. The use of foam panels applied outside of the studs necessitates the use of a plaster system specifically designed for use with foam panels. Commonly known as “one coat stucco systems” or EIFS, these plaster systems can achieve insulation in the wall system that is equivalent to Title 24 requirements or better. For instance, a home in Palm Springs could choose to use R-21 insulation between 2x6 wood studs, spaced 24 inches on center, OR R-13 batts between 2x4 wood studs with 1-1/2 inches of foam board and an insulated plaster system. See Table 1 for more details on residential CI systems. In commercial buildings using metal framing, the reasons to use CI systems are even more compelling. Because metal studs permit the transfer of more energy out of the building, their performance is improved more than wood-framed buildings by the use of foam insulation outside the studs. It would be difficult to comply with Title 24 building with metal studs without foam insulation in many climate zones, unless other significant energy upgrades were made in other parts of the building. For instance, building with a CI plaster system in San Francisco, Los Angeles, or San Diego, a builder can achieve Title 24 compliance with 1-1/2” of CI foam over 4” metal studs and R-11 batt insulation. See Table 2 for details on code-compliant CI systems for commercial structures.
Metal-framed hotels and high-rise residential have the same standards throughout the state. A U-factor of 0.105 is required, which can be met with 1 inch of CI foam over 4” metal studs with R-13 batts. Over wood framing, half the state allows a U-factor of 0.059, which can be met with 2x6 studs, R-19 batts, and R-4 CI. The most extreme zones of the state require U=0.042, which requires 2x8 studs. See Table 3 for details for use with hotels and high-rise residential projects. |
AuthorsNick Brown, CEA Archives
January 2025
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