Heat Pump Water Heater Installation

Where should a heat pump water heater be installed?

Indoors, in a space that stays mild all year. DOE and Energy Star both say these units belong in spaces that remain between 40°F and 90°F year-round, with about 1,000 cubic feet of air space around them. A.O. Smith's manual allows heat pump operation in air between 37°F and 120°F, with the elements taking over outside that range.

Good spots: a basement, a large utility room, a garage in a mild climate, or next to a furnace where there's spare heat. DOE notes a room with excess heat, like a furnace room, improves efficiency. Bad spots: a small closet with a solid door, an attic, or anywhere that freezes. The manual also says to avoid attics and upper floors, and to install where it won't freeze.

The unit cools and dries the room it's in. Energy Star says that helps in hot, humid months. In a finished basement in winter, it can make the space chilly.

Space, louvers and ducting

Numbers vary by model, so read your manual. For A.O. Smith's Voltex units:

• An unvented install needs at least 450 cubic feet of space.
• An enclosure from 84 to 449 cubic feet needs ventilation, such as a fully louvered door.
• A wall grille needs at least 22 by 6 inches, or 130 square inches of net free area.
• Clearance of at least 6 inches in front and 12 inches above the unit, and 3 feet of front clearance is recommended for service.
• Ducting can use 8-inch duct with the factory adaptors, with up to 100 feet of flexible or 300 feet of rigid duct.

Treat DOE's 1,000 cubic feet as the comfortable target and the manual's minimum as the floor. Ducting the exhaust air outside or into another room is the fix when the closet is too small or the cold air is a problem.

Tools and parts

Everything on a regular electric tank install, plus:

• Condensate tubing (A.O. Smith supplies 5/8-inch inside diameter flexible tubing)
• A condensate pump if there's no floor drain below the unit's condensate outlet
• Louvered door, grilles or duct kit if the space is tight
• A drain pan at least 2 inches wider than the tank
• An expansion tank where your system needs one
• Level, because the condensate won't drain off a tilted unit

How to install a heat pump water heater

120-volt plug-in models

Some newer heat pump water heaters run on 120 volts and plug into a standard household outlet. That can save the cost of a new circuit, which is a big deal in an older house with a full panel. A.O. Smith contrasts them with 240-volt models that need dedicated wiring and a 30-amp breaker. HomeGuide puts a new dedicated circuit at $250 to $900 and a panel replacement at $850 to $1,700, so the plug-in option can change the whole budget.

Mistakes people make

• Putting it in a closet that's too small, with no louvers. It'll run on elements and cost as much as a regular tank.
• Forgetting the condensate. A.O. Smith says these units produce condensate like an air conditioner, and an unplanned drain line ends up running across the floor.
• Mounting it next to a bedroom. A.O. Smith lists its Voltex MAX at 45 dBA, and the manual says to place it where appliance sound won't disturb anyone.
• Powering a dry tank, which can burn out the upper element.
• Skipping the filter. Clean it after the first six months and at least yearly after that.

Cost and when it's a pro job

HomeGuide puts a hybrid heat pump water heater at $2,000 to $4,600 installed, with the unit alone at $1,500 to $3,000. Energy Star notes installation may take longer than a standard water heater, so plan ahead. New circuits, panel work, ducting through walls and condensate pumps are where a licensed plumber and electrician earn their money. See heat pump water heater installation cost for details.