In an all-in-one HPWH, the heated refrigerant is usually conveyed through a heat exchanger that’s wrapped around the outside of the tank, under the insulation. The refrigerant heats the tank by conduction, transferring heat from the condenser coil through the tank shell, to the water inside.
Similar in appearance to a typical tank-style water heater, these HPWHs are convenient to install. They have a small footprint, since the heat pump is located on top of the tank. All-in-ones typically range in price from about $900 for a 40-gallon unit available at home improvement stores to more than $2,500 for an 80-gallon higher-quality unit, which has more insulation and a more durable tank. If installed by a professional, an HPWH installation should cost no more than a conventional electric water heater installation. If a homeowner feels comfortable installing an electric water heater, they should be able to install this type of system.
To meet increased demands for hot water, an all-in-one HPWH has an electric backup heater, using 240 VAC at 20 to 30 amps. The unit is hard-wired. It has hot- and cold-water plumbing connections. Maintenance is simple, with an air filter to be cleaned when it’s dirty, perhaps once or twice a year, and by regularly replacing the tank’s anode rod (see “Longer-Lived Tanks” sidebar).