Why One Homeowner’s Electricity Bills Doubled After a Heat Pump Install

One of the most common calls we receive at UK Heat Pump Help goes something like this:

"Our electricity bill has doubled since the heat pump was installed. Something must have gone wrong."

Sometimes, it genuinely has doubled. But in a significant number of cases, nothing has gone wrong at all the home has simply moved almost all of its heating demand away from gas, oil, or LPG and onto electricity instead. The bill looks alarming because electricity is now doing a job that used to be invisible across two or three separate fuel sources.

The single most important shift in thinking after a heat pump installation is this: stop looking at your electricity bill alone. Start looking at your total annual heating cost.

That one change in perspective solves most of the confusion but not all of it. Because rising electricity costs after a heat pump install can sometimes signal a genuine problem, and knowing the difference matters.

A Real Example: When Panic Set In

We recently worked with the owner of a detached property who had a new air source heat pump installed a few weeks earlier. By the time they contacted us, they were genuinely worried.

Their electricity direct debit had increased significantly. They were checking their smart meter multiple times a day. The heat pump seemed to run almost constantly. And the gas bill which used to be a predictable monthly cost had essentially disappeared.

But psychologically, the vanishing gas bill barely registered. What they saw was an electricity bill that looked nothing like it used to.

This is one of the most predictable patterns we see after heat pump installations in the UK. The numbers often look frightening in isolation. In context, they frequently make complete sense though not always, and that distinction is exactly what this article is here to help with.

Why Electricity Usage Rises After a Heat Pump Install

To understand why your electricity bill increases after a heat pump installation, it helps to understand what a heat pump actually does differently from a boiler.

A gas or oil boiler burns fuel inside the property to generate heat. You pay for that fuel separately as a gas standing charge and unit rate, or as periodic oil deliveries. Electricity runs the boiler's controls and pump, but the heavy lifting of heat generation is done by burning gas or oil.

A heat pump works entirely on electricity. It uses electrical energy to move heat from the outdoor air into your home a process that is far more efficient than burning fuel, but one that shows up entirely in your electricity bill.

So when a heat pump replaces a boiler, what changes is:

• Electricity usage rises: because the heat pump uses electricity to produce all your heating and hot water

• Gas usage drops sharply or disappears: there is nothing left to burn

• Oil deliveries stop: if you were on oil, they simply end

• LPG usage falls to zero: same principle

The household's total energy consumption for heating may be very similar or even lower but it now appears entirely in one place: the electricity bill. For homeowners used to splitting heating costs across multiple fuel types, this consolidation can feel like a sharp and unexpected increase even when overall spend has stayed flat or fallen.

The Psychology of the Electricity Bill

There is also a psychological element worth naming directly, because it affects almost everyone who makes the switch.

Gas and oil costs tend to feel abstract. A monthly direct debit for gas rarely triggers alarm in the way that a spiking electricity bill does. Oil deliveries happen a few times a year and get mentally filed away. LPG tank refills are infrequent enough to feel like one-off costs rather than ongoing heating spend.

Electricity is different. Most people check their electricity usage far more often than they ever tracked their gas consumption. Smart meters make real-time usage visible in a way that a gas meter never did. And the unit rate for electricity in the UK is significantly higher than gas so even if the heat pump is producing heat efficiently, the bill in pounds looks larger than the gas bill did.

This combination higher visibility, higher unit rate, consolidated costs creates a perfect storm of perceived alarm that does not always reflect the actual financial reality.

Comparing your total annual heating spend (gas or oil plus electricity, historically) against your new total electricity bill is the only accurate way to judge whether costs have genuinely risen.

When Higher Electricity Bills Do Signal a Real Problem

Understanding the fuel-switching explanation is important, but it should never be used to explain away a genuine efficiency problem.

Heat pumps can and do develop issues sometimes from installation, sometimes from configuration, sometimes from system design that cause them to use far more electricity than they should. These are real problems with real costs, and they are worth taking seriously.

During our Fix My Heat Pump remote diagnostic reviews, the issues we find most frequently in poorly performing systems include:

Flow temperatures set too high This is probably the single most common problem. Heat pumps are designed to work efficiently at lower flow temperatures typically between 35°C and 45°C for a well-designed system. When flow temperatures are set at 55°C, 60°C, or higher (often because an installer defaulted to boiler-like settings), efficiency drops sharply and electricity consumption rises. A heat pump running at unnecessarily high flow temperatures can use 30–50% more electricity than it should.

Weather compensation switched off or never configured Weather compensation automatically adjusts the flow temperature based on outdoor conditions running cooler on mild days and warmer on cold ones. It is one of the most effective tools for keeping a heat pump running efficiently. Many systems are installed with this feature disabled or improperly set, leaving the heat pump running at a fixed high temperature regardless of whether the weather calls for it.

Immersion heaters running constantly Most heat pump systems include an electric immersion heater as a backup for hot water or as a legionella prevention measure. When these are incorrectly scheduled or left running more than necessary, they can quietly add substantial electricity costs completely independent of the heat pump itself.

Poor or absent scheduling A heat pump works best when it runs consistently and gradually, rather than being switched on and off to match human schedules the way a boiler might be. Homeowners who apply boiler logic to a heat pump turning it off at night and expecting quick recovery in the morning often end up using more electricity than if they had left it running at a lower background temperature overnight.

Cycling problems When a heat pump switches on and off frequently in short bursts, it is almost always a sign of a problem oversizing, a faulty flow sensor, a hydraulic issue, or a control setting that is not suited to the system. Cycling reduces efficiency and increases wear on components.

Badly balanced radiators If radiators are not properly balanced, some rooms will get too hot while others stay cold. The heat pump works harder to compensate, flow temperatures may be pushed up to satisfy the coldest radiators, and overall efficiency suffers.

Controls left in default installer modes Many heat pumps leave the installation with control settings that are not optimised for the specific property. Default modes are conservative and often inefficient. Without proper commissioning adjusting settings to the actual heat loss of the property, the radiator sizes installed, and the local climate efficiency can be significantly lower than it should be.

In the case we mentioned at the start of this article, the culprit was flow temperature. Once this was corrected alongside some control improvements, electricity consumption dropped and comfort actually improved. The homeowner had been paying more and getting less a common combination when a system has not been properly set up.

How Heat Pumps Are Supposed to Run

One thing that contributes significantly to post-installation anxiety is that heat pumps simply look and sound different from boilers and many homeowners interpret that difference as a sign that something is wrong.

A gas boiler fires up, heats the system to a high temperature quickly, and then switches off. You might hear it run for twenty minutes before it cuts out. This is familiar.

A heat pump operates at much lower temperatures but runs for far longer periods sometimes continuously during cold weather. On a cold winter day, it is entirely normal for a heat pump to run for many hours without stopping. This is not a fault. It is how the system is designed to work.

The extended running allows the heat pump to maintain a steady, comfortable temperature throughout the property without the sharp heat-cool cycles of a boiler. For the heat pump to work efficiently, this continuous low-temperature approach is actually preferable to short bursts of high-temperature heat.

So if you notice your heat pump running for long stretches and worry that something is wrong in most cases, it is not. The question to ask is whether the house is comfortable and whether the electricity consumption is within a reasonable range for the size of the property and the outdoor temperatures.

How to Compare Your Running Costs Properly

If you want to assess whether your heat pump is genuinely costing more to run than your old heating system, here is the most reliable approach:

1. Add up your old annual heating costs: this means your full year of gas bills, oil deliveries, or LPG purchases, plus your electricity bills from before the heat pump was installed.

2. Compare against your new total annual electricity bill: everything in one number.

3. Consider the seasons heat pumps perform best in mild weather and work hardest in cold weather. A fair comparison needs a full year of data, not a single winter month.

4. Factor in any changes to the property: if you have improved insulation or added rooms since the old system was running, the comparison becomes more complex.

Month-to-month comparisons, particularly in the first few months after installation, rarely tell the full story. A full annual picture is what matters.

Still Not Sure Whether Your System Is Working Correctly?

If you have done the comparison and costs still feel disproportionate, or if the house simply does not feel as warm as it should, it is worth getting the system properly assessed.

Our Fix My Heat Pump service is designed specifically for this situation. We work remotely with homeowners across the UK to review system settings, analyse running data, and identify whether there are configuration or design issues driving unnecessary costs. We have helped homeowners with issues ranging from incorrect flow temperatures to complete system redesign recommendations — and in many cases, relatively small changes make a significant difference to both comfort and cost.

We have also documented a number of these cases in our case studies section, including a Victorian terrace in Bristol where lukewarm radiators on cold days turned out to be caused by heat loss in buried pipework rather than any fault with the heat pump itself a reminder that poor system design can produce symptoms that look like heat pump failure.

If you are still at the planning stage and want to avoid these problems before they start, our Pre-Installation Design & Heat Loss Review independently assesses heat loss calculations, radiator sizing, and system design before installation begins — so you have a much better chance of getting it right from day one.