Why Air Source Heat Pumps Don’t Add Up in the Real World
Air Source Heat Pumps (ASHPs) are often sold as the future of home heating. Green, efficient, and government-backed, they promise to lower your bills and save the planet. But scratch beneath the surface and the story isn’t so simple.
Let’s break it down: what ASHPs really are, how they work in the wild, and why—when you crunch the numbers—they might be more marketing hype than meaningful solution.
What Is an Air Source Heat Pump?
Here’s the science in plain English.
An ASHP works on temperature differential. It uses compression to cool a gas, runs it through a radiator where the outside air warms it slightly, then expands the gas. That expansion makes the gas hotter than it was before, and this heat is used to warm your home.
Sounds like magic. It isn’t. It’s essentially a reversed air-conditioning unit—technology we’ve had for decades.
Do They Work in Every Home?
No. And here’s why.
ASHPs don’t produce many kilowatts of heat. In a poorly insulated 1990s three-bed semi, you might need 24kW to heat the house. A 12kW ASHP only gives you a theoretical maximum of 50% of that—on a perfect day. When it’s freezing outside and the temperature differential shrinks, expect it to output closer to 4.5–6kW.
So unless your home is near-zero loss, you’re starting from a serious disadvantage.
The Financial Reality Check
Let’s talk costs.
Upfront Investment:
ASHP plus infrastructure: £15,000
Lifespan: optimistically 15 years
Servicing: £300/year (£4,500 total)
Glycol replacement: £500 every 3 years (£1,500 total)
Energy Costs:
Based on a Coefficient of Performance (COP) of 2 over 12 hours/day, 6 months/year:
Total energy benefit: £10,000 over 15 years
But installation and maintenance cost £15,000
Net loss: £5,000 compared to doing nothing special.
And remember, this is in an ideal home. In a typical UK house, the gap widens fast.
The Carbon Footprint Myth
What about CO2? Surely ASHPs are better for the planet?
Let’s compare:
| Cost/Impact | ASHP (15 Years) | Convector Heaters (15 Years) |
|---|---|---|
| Manufacturing & Installation CO2 | 17,000 kg CO2 | 748 kg CO2 |
| Electricity Use CO2 | 7,862 kg CO2 | 10,121 kg CO2 |
| Total CO2 Footprint | 24,862 kg CO2 | 10,869 kg CO2 |
| Total Cost (15 Years) | £47,000 | £42,080 |
Even with their efficiency advantage, ASHPs still leave a carbon footprint over twice as large as cheap electric heaters when you factor manufacturing and maintenance.
And convector heaters have another advantage: they’re on-demand. Turn them off when you leave the room. ASHPs can’t do that—they need to run continuously.
So Why Are We Pushing ASHPs?
The numbers don’t lie:
ASHP total cost over 15 years: £47,000
Convector heaters total cost over 15 years: £42,080
Even in the best-case scenario, ASHPs cost more and emit more CO2.
So why do they exist? Because the narrative sounds good? Because subsidies and targets favour headline technology over nuanced solutions? Because, let’s be honest, it’s easier to sell a £15k system with a government grant than a £30 heater from Amazon? What do you think, all we know is the data…
The Bottom Line
ASHPs aren’t magic. They’re old tech repackaged with green credentials, and in most UK homes its widely recognised by experts I the field that they simply don’t stack up financially or environmentally.
If you’re thinking about one, ask yourself:
Is my home super-insulated?
Can I afford to run it 24/7?
Am I okay with paying more for less heat?
If not, maybe stick with something simpler—and spend the difference on the right insulation.
Take Action!
Curious about what really works for your home? Use 1000 Trade Studios free AI quoting tool to see where your money and carbon could be best spent.
