Pool heaters & pool heat pumps compared

There are four common ways to heat an above-ground pool. Solar absorbers (solar mats or collectors) use the sun: the filter pump pushes pool water through black hoses or panels, where it warms up. That costs nothing to run but only works when the sun shines. Pool heat pumps extract heat from the surrounding air and transfer it to the water – turning one kilowatt-hour of electricity into several kilowatt-hours of heat. Electric inline heaters heat directly with electricity; they are cheap to buy but expensive to run. Wood-fired pool stoves heat the water via a heating coil.

The choice depends on pool volume, location and how warm you want the water:

Pool heat pumps are sold by heating output in kilowatts and recommended pool volume. Look at the coefficient of performance (COP), which states how much heat is produced per kilowatt-hour of electricity – it depends heavily on the outside temperature. Inverter models adjust their output and therefore run more quietly and efficiently. It's also important that the heat pump matches the flow rate of your filter pump.

For solar absorbers, the rule of thumb is that the absorber area should be at least half the size of the water surface. Point the absorbers south and connect them after the filter.

A pool loses most of its heat through the water surface – through evaporation and radiation at night. A solar cover or other cover is therefore the most effective and cheapest measure. Without a cover, much of the heating output is lost overnight. A sheltered, sunny location and an insulating mat under the pool also help.

Electric pool heaters and heat pumps must only be run from sockets protected by a residual current device (RCD). Keep to the distances from the pool specified by the manufacturer.