Home › Heat Pump Water Heater

Heat Pump Water Heater

How it works

A small heat pump on top of the tank draws air across an evaporator coil, moves the heat into the water and exhausts cooler, drier air. Backup resistance elements in the tank handle high demand. Most units offer modes such as heat pump only, hybrid and electric only.

Efficiency rating

Water heaters are rated by Uniform Energy Factor (UEF). Standard electric tanks score just under 1.0; heat pump water heaters often score 3 or more. That means roughly a third of the electricity for the same hot water in typical conditions.

Space and location

• Many units need a minimum room volume or ducting to supply enough air; check the manual.
• Ambient temperature range matters; in cold garages output falls and backup elements run more.
• The unit cools the space; in a basement that may be welcome in summer and less so in winter.
• Fan and compressor sound is similar to a dehumidifier.
• A condensate drain or pump is required.

Electrical

Many models need a 240 V circuit, often similar to a standard electric tank. Some newer 120 V plug-in models are designed for easier replacement of gas tanks. A licensed electrician should confirm circuit and panel capacity. Replacing a gas tank also involves capping gas lines and venting, which must be done by licensed trades.

Sizing

Size by first-hour rating and household peak use rather than tank volume alone. Because heat pump recovery is slower, many households choose a slightly larger tank than their old one.

Worked example

Figures below are illustrative examples (2026-10-29), not quotes or guarantees.

A household uses about 3,000 kWh a year for hot water with a standard electric tank at a UEF around 0.93. A heat pump water heater with a UEF of 3.5 would use about 3,000 × 0.93 ÷ 3.5 ≈ 800 kWh. At $0.15/kWh, yearly cost drops from about $450 to $120 in this example.

Related

See COP explained and heat pump rebates in the US or Canada for where to check incentives.

Operating modes explained

Heat pump only mode gives the lowest running cost but the slowest recovery. Hybrid mode uses the heat pump first and calls on elements during heavy demand. High-demand or electric-only mode runs elements, much like a standard tank, and is useful when guests are staying or if the compressor needs service. Vacation mode keeps the tank from freezing while using minimal energy. Many households leave hybrid as the default and switch to heat pump only when demand is light.

Recovery and first-hour rating

Recovery is slower in heat pump mode, so a family that takes several showers back-to-back may run short with a small tank. The first-hour rating on the label estimates how much hot water the unit can deliver starting from a full tank. Compare it with your busiest hour: showers, dishwasher and laundry. If your current tank sometimes runs out, choose a larger model, or use a mixing valve to store hotter water safely.

Mixing valves and scald protection

Storing water at a higher temperature with a thermostatic mixing valve increases usable capacity, but scalding risk rises if no valve is installed. Many codes require mixing valves in some cases. A licensed plumber should install and set them.

Maintenance

Clean the air filter as the manual directs, often every few months. Keep the condensate drain clear. Flush sediment and check the anode rod periodically, as with any tank. Have a technician service the heat pump section if efficiency falls.

Replacing a gas water heater

Switching from gas involves an electrician for a circuit, a plumber for water connections, and a licensed gas fitter to cap the gas line, and possibly adjusting the venting for any remaining gas appliances. Permits are often required. Plan for a condensate drain and enough air volume.

Climate and location trade-offs

In a warm climate, a garage location works well year-round. In a cold climate, a basement near the furnace usually provides stable air temperatures, and the cooling effect is minor in winter compared with the home's total heating. Some units allow ducting intake and exhaust to direct cool air outdoors or to another space.

Comparing costs

To compare yearly costs, look at the yellow EnergyGuide or EnerGuide label estimates, then adjust for your electricity rate. Include installation differences, any circuit work and expected tank life. Incentives may apply; check official sources without assuming any amount.

Space requirements

Heat pump water heaters pull heat from the surrounding air, so they need a room with enough air volume, often a basement or garage, and clearance around the unit. They also cool and dehumidify that space, which can be welcome in a damp basement but less so in a small closet. Some models accept ducting to move air in or out.

Condensate and noise

The unit produces condensate that needs a drain or condensate pump. The fan and compressor make a sound similar to a dehumidifier; avoid placing it next to a bedroom wall.

Operating modes

Most models offer heat pump only, hybrid and electric modes. Hybrid mode uses the heat pump first and the elements when demand is high.

Sizing the tank

Tank size depends on household size and peak use. A larger tank helps in heat pump mode because recovery is slower than with elements.

Cold-weather performance

When the space gets too cold, the unit switches to elements, so basement placement in very cold homes matters.

FAQ

Will it make my basement cold?

It cools the space somewhat; ducting options can help.

Is it noisy?

About as loud as a dehumidifier.

Does it work in a cold garage?

Less efficiently; backup elements run more.

Try the calculator · Back to FAQ & guides