Like standard water heaters, heat pump water heaters come in a variety of sizes. Typically, these are in the 40-50 gallon (for 2-3 people), 60-70 gallon (for 3-4 people), and 80+ gallon (for 4+ people) ranges. It's best to size your heat pump water heater to meet your current needs and, ideally, any near future increase in needs. For instance, if you’re upgrading your home water heating system and expect to have family move back home or are planning a renovation and a rental suite that will share the hot water, size up now to save money in the long-run. The size of your tank should be listed in gallons on the nameplate and on the Energy Guide (yellow) sticker of any new model.