加利福尼亚州的单户住宅建筑存量主要是燃气储水式热水器。这是建筑节能法规的结果。几十年来，在预算合规工具中计算的热水器能耗使使用电阻热水器变得很难合理。因此，几乎没有安装电热水器。合规性工具的编写方式不利于热水负荷的计算，热水器能源使用的计算时间也没有考虑到储罐的缓冲效应。预算计算的一个重要部分是使用与时间相关的发电量估值，以获取一年中每小时用电的社会成本。也就是说，蓄热式电热水器的热水使用和能耗之间的时间差的实际影响没有得到适当的评估。 这些疏忽的综合影响无意中阻碍了加州新建筑采用热泵热水器，这是实现该州净零能源和温室气体排放目标的主要障碍。本文介绍了《建筑能效规范》目前计算热水器能源预算的方法。解释了计算过程中存在的问题。近年来，我们对住宅热水系统的了解大大增加，大大提高了我们描述这些系统的能力。基于这一增加的知识，建议对建筑规范计算进行修订。RESNET最近采用了增强型热水负荷计算器。过去几年对住宅热水抽取模式的详细现场研究为计算中使用更现实的抽取时间表提供了来源。 为西北地区的公用事业激励计划开发的开源水热模拟模型可用于计算能源使用量和时间。还讨论了需求响应控制在减少电热泵热水器对电网影响方面的作用。引用:2016年冬季会议，佛罗里达州奥兰多，会议论文

California's single-family residential building stock is dominated by gas-fired storage water heaters. This is a result of the building energy efficiency code. For decades the water heater energy consumption calculated in the budget compliance tools has made it hard to justify using an electric resistance water heater. As a result very few electric water heaters have been installed. The compliance tools were written in a way that poorly calculates the hot water load and the calculated time of water heater energy use does not account for the buffering effect of a storage tank. An important part of the budget calculation uses a time dependent valuation of electrical generation to capture the societal costs of using electricity for every hour of a typical year. Meaning the actual effects of the time difference between the hot water use and the energy consumption of electric storage water heaters are not being evaluated properly. The combined effect of these oversights has inadvertently blocked adoption of heat pump water heaters in new construction in California, a major obstacle for reaching the state's net-zero energy and greenhouse gas emission targets. This paper describes the way the building energy efficiency code currently calculates the water heater energy budget. Problems in the calculation procedure are explained. Our knowledge about residential hot water systems has increased greatly in recent years, significantly improving our ability to characterize these systems. Revisions to the building code calculations are suggested based this increased knowledge. An enhanced hot water load calculator has recently been adopted by RESNET. Detailed field studies over the past several years of residential hot water draw patterns provide a source for more realistic draw schedules to use in the calculations. An open source water heat simulation model developed for utility incentive programs in the Northwest could be adapted to calculate the amount and timing of energy use. The role of demand response controls to reduce the impact of electric heat pump water heaters on the grid are also discussed.