Does it work in a cold garage?

It needs air above a minimum temperature. In a cold space the design either uses a different location or a unit rated for colder air.

Why is recovery slower?

The unit heats at a lower rate than a resistance element. A larger tank or a different setpoint keeps up with demand.

What about the drain?

Condensate has to go somewhere. A drain line or a condensate pump is part of the install.

How heat pump water heaters work

A heat pump water heater moves heat from the air around it into the tank instead of making heat with a burner.

Water heating runs every day of the year, which is why it shows up so clearly in the running cost. A heat pump water heater changes that cost by moving heat instead of burning fuel to make it.

How it works

The unit pulls warmth out of the air around it and moves that heat into the tank. A small compressor and a fan sit on top of the tank. The air leaving the unit is cooler and drier, which is also why it can pull humidity out of a basement.

Because it moves heat instead of making it, the unit uses far less electricity than a standard electric resistance tank. Recovery is slower, so the tank size and the household demand are matched in the design.

Key terms

First hour rating is how much hot water the tank can supply in the busiest hour.
Coefficient of performance is how much heat the unit moves per unit of electricity.
Recovery time is how long the tank takes to heat back up.
Condensate is the water the unit pulls out of the air, which needs a drain path.

Where it fits in a project

Water heating connects three trades. It needs electrical capacity for the compressor, a place for condensate to drain, and enough space around the tank for air to move. It also changes the load a heat pump and a solar array are sized against, so it belongs in the same proposal as the rest of the project.

Filed under Water Heating explainers in the Learn hub.