Technical explainers
Here are some short guides to help you understand how things work, what’s involved and some terminology explanations.
An air source heat pump works just like a refrigerator, but in reverse. Instead of cooling the air inside a box, it pulls warmth from the outside air and moves it into your home.
The Simple Cycle:
- Gather Heat: A fan draws outside air over a coil containing a cold liquid refrigerant. Even in cold weather, there is enough heat to warm this liquid.
- Turn to Gas: As the refrigerant warms up, it boils and turns into a gas.
- Boost Temperature: This gas goes into a compressor. Squeezing the gas increases its pressure and makes it significantly hotter.
- Warm Your Home: The hot gas travels to a heat exchanger, where it passes its heat to the water flowing through your radiators or underfloor heating (and your hot water cylinder).
- Reset: After giving up its heat, the gas cools down, turns back into a liquid, and passes through a valve to lower its pressure. It is now ready to start the cycle again.
Why it’s efficient: The pump doesn’t burn fuel to create heat; it simply moves existing heat from outside to inside using electricity. This makes it incredibly efficient, delivering over 350% energy efficiency compared to about 90% for a standard A-rated gas boiler.
The Microgeneration Certification Scheme (MCS) is the UK’s trusted, government-backed quality mark for small-scale renewable technologies including heat pumps.
By setting and maintaining rigorous industry standards, MCS ensures that both products and installers meet high benchmarks for safety and performance, giving consumers confidence in their green energy investments. This certification not only guarantees quality but also unlocks access to key financial incentives, including the Boiler Upgrade Scheme (BUS).
Think of a heat loss calculation as a “thermal check-up” for your home. It figures out exactly how much heat your house loses on the coldest days (usually around -2°C to -3°C), so an air source heat pump (ASHP) can be sized perfectly to keep you cozy without wasting energy.
Here’s what it involves:
- Fabric heat loss: How much warmth escapes through walls, windows, roofs, and floors based on their size, material, and insulation.
- Ventilation heat loss: Heat lost through drafts and air leaks.
- Room-by-room analysis: Ensures every space gets the right amount of heat, whether you’re using radiators or underfloor heating.
Getting this right means your heat pump runs at low flow temperatures, stays highly efficient, and keeps your home comfortable all winter.
Flow temperature is simply the temperature of the hot water that leaves your heat pump and travels through your pipes to your radiators or underfloor heating system. It’s the “delivery heat” your home feels. Heat pumps work best at lower temperatures. The lower your flow temperature, the more efficiently your heat pump runs, using less electricity to keep your home warm.
Setting the right flow temperature is the single most important step to maximizing efficiency and saving money on your energy bills.
Your running costs depend on four main things:
- Home Heat Demand: Bigger or draftier homes need more energy to stay warm.
- Efficiency (COP): A higher Coefficient of Performance means more heat for less electricity.
- Insulation: Good insulation stops heat escaping, lowering your bills.
- System Size: A correctly sized pump runs more efficiently than one that is too big or too small.
Quick Wins: Set a steady temperature, keep the outdoor unit clear, and consider smart energy tariffs to save up to £500 a year compared to gas boilers.