What is a hybrid water heater, and does it work in a Phoenix garage?

A hybrid heats water by moving heat instead of making it. ENERGY STAR explains that heat pumps "use electricity to move heat from one place to another," here from the surrounding air into the water, rather than generating heat directly. A fan draws room air across a cold coil, the coil picks up heat, and a compressor passes that heat to the tank.

Because it has both a heat pump and electric elements, a hybrid can run in different modes. Rheem's ProTerra spec sheet, for example, lists these operation modes:

The efficiency comes from the heat pump. ENERGY STAR says a certified hybrid "can save a family of four an estimated $550 a year on their energy bill" compared with a standard electric resistance water heater. Those savings are ENERGY STAR's national estimate, not a Phoenix quote, and they assume the heat pump does most of the work.

Yes, with one caveat: a hybrid is happiest in a space that stays mild, and a Phoenix garage in July isn't mild. ENERGY STAR's installation guidance says hybrids "should be installed in interior spaces that remain between 40° to 90° F year-round, and provide 1,000 cubic feet of air space around the water heater."

That 40 to 90 degree range is a best-practice target, not a hard limit. Manufacturers rate their units wider. Rheem's spec sheet lists an ambient operating range of 37 to 145°F for its ProTerra hybrid. So the heat pump keeps running in a hot garage. What you should expect in a Phoenix garage:

• Summer: Warm air helps a heat pump. ENERGY STAR even suggests "installing in a space with excess heat, such as a furnace room." Still, check the model's upper operating limit against your garage, especially one that faces west with no insulation.
• Winter: Cold is the harder case. ENERGY STAR says that in colder spaces with colder incoming water, hybrids "may need to go temporarily into a back-up standard electric water heating mode," which uses more energy. A garage that stays mild in winter avoids most of that.
• Side effect: ENERGY STAR notes a hybrid "can help cool and dehumidify the space it is installed in." In a garage, that's a small bonus in summer.

The place a hybrid struggles is a small closet. ENERGY STAR's experts write that efficiency "will suffer in confined spaces, like closets," and recommend at least 700 cubic feet of surrounding air, "approximately the size of a 10-foot by 10-foot utility room with a 7-foot ceiling." A two-car garage clears that easily. An interior closet usually doesn't, unless it gets louvered doors or ducting that the manufacturer allows.

A hybrid needs power, air, a drain, and the same safety parts as any tank. The plumbing code Phoenix uses says water heaters "shall be installed in accordance with the manufacturer's instructions," so the model's manual has the final word. The common requirements:

1. 1Electrical. ENERGY STAR says the most common hybrids need "a dedicated 240 Volt outlet," which suits a home that already has an electric water heater. Rheem's ProTerra is rated at 208 to 240 volts and 30 amps. For homes replacing gas, ENERGY STAR notes that models running on a standard 120-volt outlet "are now available in many markets."
2. 2A condensate drain. Pulling heat out of the air also pulls out moisture, which drips off the cold coil. The Rheem unit has "3/4" condensate drain connections." Phoenix's plumbing code requires condensate "from all cooling coils and evaporators" to be piped "to an approved place of disposal," sloped at least 1/8 inch per foot. So the line needs a real destination, such as a drain, a laundry standpipe, or a condensate pump, not a puddle on the slab.
3. 3Height and clearance. The heat pump sits on top, so hybrids are taller than standard tanks. Measure the space, and leave room to service the fan and filter.
4. 4A relief valve and pan. Like any storage tank, a hybrid needs a temperature and pressure relief valve under Section 504.4, and a pan where a leak would cause damage under Section 504.7.
5. 5Maintenance. ENERGY STAR says hybrids "may also require annual maintenance, including changing air filters."

If the hybrid replaces a gas water heater, the gas line to the old heater has to be capped safely, which is a job for a licensed plumber.

SRP runs a heat pump water heater rebate for its residential electric customers. Its program terms set the rules:

• The home must be a "permanent SRP residential electric customer" home: a single-family house, attached home, mobile home, or apartment or condo.
• The unit must have a Uniform Energy Factor (UEF) of 2.8 or better.
• The application must be filed "within six months of the installation date."
• "Rebates are not available for new construction," and a customer can get the rebate once "every 10 years."
• You need a completed application and "a dated copy of the paid invoice," and SRP may inspect the installation.

The terms point to savewithsrp.com or SRP's rebate line at (602) 264-3108 for "current program requirements, rebate amounts and program effective dates," so check there before you buy. APS customers should check APS's current residential offers, which change by program year.

A hybrid makes the most sense when you already have an electric water heater, a garage or large utility room, and a drain nearby. It makes less sense in a tight interior closet with no way to bring in more air, or where there is nowhere to run the condensate line. ENERGY STAR also advises planning ahead, since "Your installer may need time to order the proper model, and it may take longer to install than a standard water heater."

Our page on gas vs electric water heaters compares the three main types side by side, and what size water heater you need covers tank sizing. Before a garage install, check the 18 inch rule for garage water heaters and whether you need a permit to replace a water heater in Phoenix.

HQ Plumbing & Air installs and replaces water heaters across the Phoenix area, with free estimates and upfront pricing. See our water heater service.

Heat pump on top, tank below, a drain beside it. Give it air and it pays you back.