The COP is roughly equivalent (but more forgiving) than the UEF rating. Many new heat pump water heaters have a UEF of 4 [1], but this accounts for things like

The COP is roughly equivalent (but more forgiving) than the UEF rating. Many new heat pump water heaters have a UEF of 4 [1], but this accounts for things like standby losses, so the COP of the heat pump itself is higher than that. Some premium hot water heaters like the SanCO2 can achieve COP of up to 5.0 [2], so high that they don't need backup resistance elements, even in northern climates. 1. https://www.energystar.gov/productfinder/product/certified-water-heaters/results https://www.energystar.gov/productfinder/product/certified-w... 2. https://www.smallplanetsupply.com/small-planet-blog/2021/1/7/the-fundamentals-of-game-changing-hot-water https://www.smallplanetsupply.com/small-planet-blog/2021/1/7...