Your oil or gas boiler is costing you money. It’s also adding to your carbon footprint. For many homeowners, energy security is becoming a real concern too.
An air-to-water heat pump is one of the most effective ways to tackle all three problems at once.
This guide answers the most common questions homeowners ask before making the switch, and explains why a proper assessment is the essential first step.
What is an air-to-water heat pump — and how does it work?
An air-to-water heat pump takes heat from the outside air and feeds it into your existing wet central heating system. So it works with the same pipes and radiators you already have. It operates on the same principle as a fridge – just in reverse.
Because it runs at a lower temperature than a boiler, it works best when left on for longer periods. Your radiators will feel warm rather than hot. However, they’ll keep your home consistently comfortable throughout the day.
Alongside space heating, an air-to-water heat pump also heats water stored in a cylinder for your taps, showers and baths, replacing your existing hot water system in full.
A built-in backup heater handles the weekly legionella cycle and provides cover in the unlikely event of a breakdown.
Why make the switch? The case for a whole-home retrofit
Consistent home comfort
Even, steady warmth throughout the day - no cold spots, no waiting for the boiler to fire.
No fossil fuels at home
Eliminate your oil, gas and solid fuel bills entirely. Run your heating on electricity alone.
Reduced emissions
Cut your household greenhouse gas output significantly, especially as the grid gets greener.
How efficient is a heat pump, really?
This is where heat pumps genuinely outperform conventional heating. The key metric is the coefficient of performance, or COP: for every kilowatt of electricity used to run the system, up to four kilowatts of heat energy are delivered into your home.
Can I keep my existing radiators?
In many cases, yes – but every radiator in the home will be assessed to confirm it’s sized correctly for the lower flow temperatures a heat pump operates at.
A gas boiler drives radiators hard in short bursts; a heat pump runs them at a gentler, sustained temperature for longer. If any radiators are undersized, they may need to be upgraded as part of the installation.
"Insulating well before installation means a smaller, cheaper-to-run heat pump And better results year-round."
Does insulation matter?
“Insulation is one of the biggest factors affecting your heat pump’s size and running costs.
For example, heat loss through walls, roofs and windows directly increases the heating load the system must meet.
So by insulating first, you can reduce that demand. This usually means a smaller unit, and therefore cheaper to run over its lifetime.
This is one of the key reasons why an expert assessment matters so much.
It’s not just about picking a heat pump, it’s about understanding the full picture of your home’s energy performance.
Where does the equipment go?
The external unit is mounted outside the home, positioned not too far from the internal unit.
The internal unit is typically housed in a hot-press or a suitable storeroom.
Your existing hot water cylinder will be replaced with a new one designed for the heat pump system.
What size heat pump do I need?
There’s no one-size-fits-all answer. The right size depends on an accurate calculation of your home’s heating demand, which accounts for the heat lost through your specific walls, windows and roof.
This assessment must be carried out by qualified specialists – guessing leads to a system that’s either underpowered or inefficiently oversized.
Will I use a lot more electricity?
Yes, your electricity consumption will increase because you’re now using it for heating. But you’ll completely eliminate your oil, gas or solid fuel costs.
When you factor in the heat pump’s COP of up to 4, most households come out ahead on overall energy spend.
What about my hot water?
The heat pump handles all your domestic hot water – taps, showers and baths. A new hot water cylinder is installed as part of the retrofit, replacing your existing one.
The heat pump contains a backup heater for completing a legionella cycle once a week or backup in the event of a breakdown.
Are heat pumps environmentally friendly?
Yes, provided the home is well insulated and the system is correctly installed and sized.
A heat pump running in a poorly insulated property will still work, but its environmental advantage is maximised when heat loss is minimised.
How much servicing does a heat pump need?
The heat pump unit itself – like a fridge – typically requires very little servicing.
However, the full system should be checked annually by your installer or the manufacturer’s personnel to keep everything running at its best.
The right starting point: a free home energy assessment
Every home is different. The insulation levels, the age of the building, the size of the rooms, the existing radiator layout – all of these affect which heat pump is right for your property, how it should be configured, and what, if any, preparatory work will give you the best return.
The only way to get that right is to have an experienced, qualified specialist assess your home in person. That’s exactly what our free home energy assessment is designed to do.