A heat pump backup heater is an electric element that tops up heat when the heat pump can’t do the job alone, for example in very cold weather, during some defrost cycles or if the system develops a fault. Used occasionally, it’s normal. If it runs a lot, it can push up your electricity bill quickly, because direct electric heating costs far more to run than the heat pump itself. If your bills have jumped this winter, our heat pump engineers can check settings for homes in Trowbridge, Frome and nearby.
Two kinds of electric backup
The booster or backup heater for heating
Some heat pump systems include an electric heater, either inside the unit, in an indoor hydraulic module or in a buffer tank. It can add heat to the water going round your radiators when the heat pump is struggling to keep up.
The immersion heater in the hot water cylinder
Most heat pump systems with a hot water cylinder also have an immersion heater. This is often used to top up hot water to a higher temperature on a schedule, and as a backup if the heat pump can’t heat the cylinder.
Both use electricity directly. One unit of electricity in gives roughly one unit of heat out, while a working heat pump typically delivers several units of heat for each unit it uses.
When a backup heater should switch on
It’s normal for a backup heater to run occasionally:
- During a hard frost or a long cold spell, if the system is set up to allow it
- On some systems, to support the heat pump during a defrost cycle
- For scheduled hot water top-ups
- If the heat pump has a fault and goes into an emergency mode to keep the house warm
Brief, occasional use shouldn’t make a big difference to your bills.
Signs it’s running more than it should
- Your electricity use jumps noticeably in cold weather, more than you’d expect
- The controller or app shows the backup or booster heater as active for long periods
- Hot water is always being heated by the immersion rather than the heat pump
Common reasons for too much backup use
- Settings. The point at which the backup heater is allowed to start can be set too high, so it switches on before the heat pump really needs help.
- Flow temperature too high. Asking the heat pump for very hot water makes it work harder and can bring the backup in sooner.
- Hot water settings. A cylinder set to a high temperature, or with the immersion scheduled too often, uses more electricity than needed.
- Sizing or radiator issues. If the heat pump or radiators are too small for the house, the backup may fill the gap every cold day.
- A fault. If the heat pump itself stops working properly, the backup heater may quietly take over.
What you can check yourself
You can safely look at your controller or app to see when the backup heater runs, compare electricity use with the weather, and check the hot water schedule. Make a note of anything that looks odd.
Leave changes to backup heater settings, refrigerant circuits and electrical work to your installer or a qualified heat pump engineer.
Heat pumps in Trowbridge, Frome and Westbury
Heat pumps across West Wiltshire and the Somerset border are fitted in everything from new-build estates to older stone and brick homes. Older properties around Frome and Westbury can lose heat faster on a cold, windy night, which is when a well-set-up system really shows its value. A quick review of settings before the coldest weeks can make a noticeable difference to running costs. Our energy saving tips page has more general ideas.
Frequently asked questions
Is it normal for my heat pump backup heater to come on?
Yes, occasionally. Many systems use it during very cold weather, some defrost cycles or for scheduled hot water top-ups. It becomes a problem if it runs for long periods every day, because direct electric heating is much more expensive. If you’re not sure how often yours runs, check your controller or ask your installer to review the settings.
Can I turn off my heat pump backup heater?
It depends on the system, and it’s best not to change it yourself. Some backup functions protect the system from freezing or keep the house warm during a fault. An engineer can adjust when the heater is allowed to start so it only runs when genuinely needed, rather than switching it off completely.
Why is my electricity bill so high with a heat pump in winter?
Heat pumps use more electricity in winter because demand for heat is higher. A big jump can also point to the backup heater running too often, a flow temperature set higher than needed or hot water settings that lean on the immersion. A settings check by an MCS certified installer or heat pump engineer is a good place to start.
Worried your backup heater is running too much?
Give us a call on 01225 708562 or drop us a message and we’ll check your heat pump settings and help you get the running costs back under control.