Complying with heat pump water heaters in California is more difficult than it may seem. The technology can be 2.5 to 3 times more efficient than natural gas, but that does not always make compliance easier. The proposed Joint Appendix JA13 would change that and allow projects to realize the full savings potential offered by the more efficient technology.
When it comes to decarbonizing our buildings or meeting an all-electric ordinance, heat pump water heaters are one of the most discussed technologies. This technology comes with a new set of design challenges beyond the logistics of space and location. There are hidden concerns for residential applications. These challenges have to do with Title 24 compliance, the effect that they have on the cost of energy, and the effect that they have on the electrical grid.
After the daily spike in hot water use in the morning between 5:00 and 8:00 am, there is another period of high demand for hot water during the hours of 4:00 to 9:00 pm. Cooking, dishwashing, and laundry all contribute to this peak. These evening hours are also when there is the greatest demand for electricity. Having another electrical appliance that also operates during this peak will add more stress to the electrical grid.
In an effort to alleviate this stress during peak hours, codes and energy pricing have shifted. Time of Use (TOU) electrical rates are 2.5 to 3 times the cost per kWh during the peak evening hours as they are for the rest of the day. For Title 24 Energy Code compliance, California uses Time Dependent Valuation (TDV) to give weight to energy use at different times of the day. Every hour of the year has a value for natural gas and for electricity. While natural gas stays fairly even throughout the day, electricity during peak hours during summer can be 10 times more costly than it is in the morning hours. As a result, even though the technology is two to three times more efficient, heat pump water heaters are not necessarily the most effective option to increase a project’s Title 24 compliance margin.
Load shifting is one answer to all these problems. A heat pump water heater with a large enough storage tank could produce the majority of its hot water during off-peak hours, alleviating some of the additional stress to the grid. If water heating stopped during peak hours, it would be less expensive for customers paying TOU rates. If water were heated when TDV values were lower, noticeable savings in Title 24 compliance could be realized.
There is a proposal in front of the California Energy Commission that is gaining traction. The proposed Joint Appendix JA13 would codify this load shifting. Heat pump water heaters that carry the JA13 designation would be able to apply the advantages of load shifting for Title 24 energy compliance. In the proposal, a JA13 heat pump water heater would need to meet minimum safety, performance, and storage requirements. Additionally, to qualify, the heat pump water heater would be required to be capable of accepting and electronically storing the time of use schedules. With this technology, heat pump water heaters would then primarily heat water during the off-peak times.
JA13 offers a path to take advantage of these savings in an energy model. This will make it easier and less expensive to go all-electric, qualify for rebates, and earn more LEED points. It will also make the cost of water heating with electricity comparable to natural gas.
If your project is subject to an all-electric ordinance or you want to do your part to decarbonize, call Moe Fakih!
Contributing Writer: Glen Folland, Director of Sustainability
Moe Fakih, Principal