It will soon become clear that converting UK housing stock to low output heat pumps is really difficult.

You’ll need more than a plumber. Trust me on this. https://www.telegraph.co.uk/opinion/2021/04/21/governments-green-ambitions-will-come-enormous-cost/

Let’s take a typical 3-bed semi with a combi boiler providing heating and hot water.

A combi boiler can fit in a kitchen cabinet and provide output on demand.

To replace it with an air source heat pump, you’ll need to add a water cylinder and expansion vessels. Outside you’ll need space for the pump.

It can’t go anywhere, though. Space around the pump determines performance.

The 1:3 coefficient of performance of heat pumps is only true in ideal conditions.

But let’s say that the house we’re talking about has an ideal location.

The first thing you have to do is find somewhere to put the cylinder. Here’s one we installed in a new build designed for it.

Let’s put it in the spare room. We weren’t planning on guests or more kids.

Let’s heat our home!

But it typically provides water at 55 degrees. That’s not going to provide enough heat to your existing radiators. So you’ll change my rads, I hear you say.

Hang on.

Heat output works by surface area. For instance, a steam iron might have 1500W load/output, but the small surface area cannot heat a room. It’s the same with radiators.

For air source, you’ll need much bigger aluminium radiators or, ideally, underfloor heating.

Ok. Let’s go for retrofit underfloor. There are two options.

You can either fit to existing floors using a track system (insulation?), or reduce the floor levels (very very expensive).

The track system sounds best. Let’s do that.

Ok. You’ll lose your existing floor coverings, take every door off, trim and rehang to suit the new increase in floor level.

What about skirting boards and architrave? You’ll have to change that too.

Furniture? You’ll have to move it out or between rooms while the work is being done. Better still, move out for a while.

Let’s change the radiators instead. It’ll be easier.

Micro bore system? It has to come out. Sound expensive? It is.

Bigger radiators? Yep, lose some furniture.

Aluminium? Sounds expensive. They are.

I could go on.