对两种不同型号的190升（50加仑）家用电热水器进行了测试，以调查由于下部加热元件附近的陡峭温度梯度而在确定其能效时出现的问题。这种梯度使确定平均水箱水温变得困难，因为根据当前的测试标准，仅在热水器内的六个离散位置进行温度测量。结果表明，确定该平均温度的误差会对能量因数产生显著影响，因为它会导致对储罐内储存能量的不准确估计。 存储能量的估算是校正算法的一部分，该算法用于将实验室测量的效率标准化为定义能量系数的标准条件。调查结果表明，应努力确保测试开始时的条件与测试结束时的条件相似。对于这里测试的两台热水器，最好从24小时怠速开始。单位:双引文:ASHRAE交易，第114卷，pt。2、盐湖城2008

Two different models of 190 L (50 gallon) residential electric water heaters were tested to investigate problems that arise in determining their energy efficiencies due to the steep temperature gradient near the lower heating element. This gradient makes the determination of the average tank water temperature difficult because, in accordance with current test standards, temperature measurements are made at only six discrete locations within the water heater. Results show that errors in determining this average temperature can have significant effects on the Energy Factor by yielding inaccurate estimates of the stored energy within the tank. This estimate of the stored energy is part of the correction algorithm used to normalize the lab measured efficiency to the standard conditions that define the Energy Factor. The investigation’s findings suggest that efforts should be made to ensure that conditions at the start of a test are similar to those at the end. For the two water heaters tested here, this scenario was best achieved by starting with a 24 hour idling period.Units: Dual