Heat pump vs gas boiler
| Heat Pump | Gas Boiler | |
| Efficiency | 300% | 90% |
| Running costs | £500–£800/yr | £800–£1,200/yr |
| Lifespan | 20+ years | 10–15 years |
| Carbon | Zero on-site | 2.7 tonnes/yr |
Advice from MCS-Certified Installers
How Do Heat Pumps Work?
Plain English guide from MCS-certified installers. No jargon, no sales pitch — just how they actually work.
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The Science Made Simple
How a heat pump works in 5 steps
A heat pump extracts heat from outside air and uses it to warm your home. Here's how.
1
Air Is Drawn In
A fan draws in outside air across an evaporator. This works even when it's freezing — heat pumps operate efficiently down to -20°C.
2
Refrigerant Absorbs Heat
A liquid refrigerant circulating through the evaporator absorbs the heat energy from the air and turns into a gas.
3
Compressor Concentrates Heat
An electrically powered compressor squeezes the gas, concentrating the heat to a much higher temperature — typically 45-55°C.
4
Heat Is Transferred
The hot gas passes through a heat exchanger, transferring its heat to your central heating system and hot water cylinder.
5
Cycle Repeats
The refrigerant cools back down, returns to a liquid, and cycles back to the evaporator. The process repeats continuously.
Straight Answers
Common questions answered
The questions we get asked every week, answered honestly.
Do heat pumps use gas?
No. Heat pumps run entirely on electricity. No gas connection needed, no gas safety certificate, no carbon monoxide risk. You can disconnect your gas supply entirely.
Do heat pumps work in cold weather?
Yes. Modern air source heat pumps work efficiently down to -20°C. The refrigerant boils at around -30°C, so there is always heat energy to extract — even on the coldest UK winter days.
Do heat pumps use radiators?
Yes. Heat pumps work with your existing radiators. Because they run at lower flow temperatures than boilers, some radiators may need upsizing — but many homes need no changes at all.
Do heat pumps run all the time?
They modulate — running low and steady rather than cycling on and off like a boiler. This is more efficient. Think of it like cruise control vs stop-start driving.
How efficient are heat pumps?
300-400% efficient. For every 1kW of electricity a heat pump uses, it produces 3-4kW of heat. A gas boiler manages 90% at best. That's why running costs are lower.
What about hot water?
A hot water cylinder is included as part of the installation. It works just like a boiler system — the heat pump heats the cylinder, and you draw hot water from it as normal.
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Got Questions?
Frequently asked questions
Straight answers to the most common heat pump questions.
What is a heat pump?
A heat pump is a device that extracts heat from outside air to warm your home and hot water. Think of it as a fridge in reverse — instead of pulling heat out of a box, it pulls heat out of the air and pushes it into your home.
How do heat pumps work in winter?
They extract heat from the air even at temperatures as low as -20°C. The refrigerant inside the heat pump boils at around -30°C, so there is always heat energy to capture — even on the coldest UK days.
Do I need to replace my radiators?
Not always. We check every radiator during the survey. Heat pumps run at lower flow temperatures than boilers, so some radiators may need upsizing to deliver the same heat output. Many homes need no changes at all.
Are heat pumps expensive to run?
No. Heat pumps are typically 30–50% cheaper to run than gas and 60–70% cheaper than oil. For every 1kW of electricity used, you get 3–4kW of heat.
How long does installation take?
Typically 2–5 days depending on the complexity of the installation. A straightforward swap from a gas boiler with no radiator changes is usually 2–3 days.
Do I need planning permission?
Usually not. Most air source heat pumps fall under permitted development rights, so no planning application is needed. There are some exceptions for listed buildings and certain conservation areas — we check this during the survey.
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