Heat Pump Using Too Much Electricity (UK Guide)

Why Is My Heat Pump Using So Much Electricity?

I get this question from homeowners every week, and the answer is almost never 'your heat pump is broken.' In the vast majority of systems I review, high electricity usage comes down to one of a handful of configuration and design problems that are completely fixable once you know where to look.

Heat pumps are genuinely efficient machines. When a system is running as it should, a modern 8kW unit might draw 2kW of electricity to produce 8kW of heat a COP of 4. That's four times more efficient than a direct electric heater. So when a homeowner tells me their bills are eye-watering, something has gone wrong in the design, the setup, or both.

What Does 'Normal' Electricity Usage Actually Look Like?

There's no single correct answer because it depends on your property size, insulation, the outdoor temperature, and how your system is configured. But as a rough guide for a typical 3-4 bedroom UK home:

• A well-configured heat pump might use 3,000–5,000 kWh of electricity per year for heating

• During a cold snap (below 3°C), daily usage of 20–30 kWh is not unusual

• In mild weather (8–12°C), a good system might use under 10 kWh per day

If you're significantly above these figures in mild weather, that's the clearest sign that something is wrong.

In one real case we reviewed, a heat pump was consuming unusually high electricity during summer because of a misconfigured hot water setup — read the full breakdown in our heat pump high electricity bills hot water setup case study.

The Six Most Common Causes of High Running Costs

1. Flow Temperature Set Too High

This is the single biggest driver of high electricity bills in heat pump systems. Flow temperature is the temperature of the water leaving the heat pump and entering your radiators. Every degree you raise this temperature reduces the heat pump's efficiency (COP). Running at 55°C instead of 45°C can increase your electricity consumption by 25–30% for the same heat output.

A well-designed system targeting 40–45°C flow temperature in cold weather will always outperform one running at a fixed 50–55°C. If your installer set a fixed high flow temperature and left it there, this is almost certainly costing you money.

2. Weather Compensation Turned Off or Set Incorrectly

Weather compensation automatically reduces your flow temperature when it's mild outside and increases it when it gets cold. It's one of the most important efficiency features on any heat pump — and one of the most commonly disabled or misconfigured settings I find during reviews.

When weather compensation is turned off, your system runs at the same high flow temperature regardless of whether it's 14°C or -2°C outside. In a typical UK winter, mild days make up the majority of the heating season. Running at full temperature throughout wastes a significant amount of electricity.

3. The System Runs Constantly Without Reaching Temperature

Heat pumps are designed to run for long, steady periods unlike boilers that fire up intensely and stop. But there's a crucial difference between a system running steadily and efficiently versus one running constantly because it can't keep up with the heat demand. If your home never quite reaches the temperature you've set, and the heat pump never stops, it's working inefficiently — and your bills will show it.

This usually points to undersizing, inadequate radiators, or both. See the radiators section below.

4. Radiators That Are Too Small for Low-Temperature Heating

This is one of the least understood issues in heat pump performance. Every radiator has a heat output rating but that rating is measured at a specific temperature difference called Delta T 50 (the mean water temperature is 50°C above room temperature). This is perfect for a boiler running at 70–80°C but completely wrong for a heat pump running at 40–45°C.

At Delta T 20 (typical for a heat pump), your radiators produce roughly 40% of their rated output. If radiators weren't upgraded when the heat pump was installed, the system may be physically incapable of heating your home at efficient flow temperatures so it compensates by running at higher temperatures and for longer. The result is higher bills.

5. Backup Heater Running More Than It Should

Most heat pump systems include a backup electric heater (sometimes called an immersion or auxiliary heater) that kicks in during very cold weather or when the heat pump can't keep up. In a correctly designed system, this backup element should run rarely perhaps during the coldest 20–30 hours of a UK winter. If it's running for hours every day, there's a problem with the main system.

Electric backup heaters typically draw 3–6kW directly no efficiency multiplier. If yours is running frequently, it's costing you significantly more than it should, and it's masking an underlying design or configuration issue.

6. Poor System Balancing and Hydraulic Issues

If some radiators are getting too much flow and others too little, the heat pump has to work harder and run longer to achieve even heating across the property. Hydraulic imbalance is common in systems where the installer didn't commission the circuit properly after installation. You can often spot it when some rooms are always warm and others always cold, even with TRVs fully open.

What a Well-Performing System Should Look Like

When I review a system that's running well, I typically see: flow temperatures between 35–48°C modulating with outdoor temperature, the backup heater rarely or never activating, the heat pump cycling off occasionally in milder weather once target temperature is reached, and electricity consumption that broadly tracks the outdoor temperature.

If your system doesn't match this picture, the good news is that in most cases, the fix doesn't involve replacing any hardware. It's configuration and that's something a proper technical review can identify and address.

If your system does not match that picture and you want to work through the symptoms methodically before booking a full review, our Heat Pump Troubleshooting Support page outlines the options for getting structured technical help.

Need Help Working Out What's Causing Your High Bills?

If your heat pump is costing more to run than you expected, a full system performance review will pinpoint exactly what's driving the usage whether that's flow temperature, weather compensation, radiator sizing, backup heater runtime, or hydraulic balance. You'll receive a written report with specific, actionable recommendations.

If you're still in the planning stage, a pre-installation design review checks whether your proposed system is correctly sized and designed to run efficiently preventing these problems from occurring in the first place.