Are Heat Pumps the Future?

The latest government announcement offers homeowners an incentive of up to £5,000 to fit a renewable source heat pump instead of a gas boiler in a bid to help the UK meet its net carbon goals.

For the end-user, this may seem an excellent benefit when it comes to finally changing their boiler because according to the energy-saving trust, it costs an average of £2,300 to replace a boiler, and a heat pump can be between £6,000-£8,000, of course, this depends on system size and complexity. So, having £5,000 knocked off the bill will be very tempting to the end-user.

However, the issue is not as simple as it may first seem. We’ve listed some potential challenges below, with assumed costs so you can see where the pitfalls may lie.

The age of properties

What seems to be missing with this grant is the lack of focus on increasing the home’s efficiency first. With over half the UK houses being 1980’s and older, we can expect to heat losses of around 60w/m² + per room. Meaning the demand for the emitter and, more importantly, the heat pump is huge. Therefore, for a heat pump to operate effectively, the home must reduce its heat losses to significantly affect carbon reduction and cost. Below are some indicative prices to insulate a standard size UK home.

Extra cost. Insulate lofts: £1000+
Extra cost. Fitting efficient double glazing windows throughout £3500- £4000 for eight units.
Extra Cost. Retrofit external wall insulation. £15,000 (based on a 3-bed detached house)

2. The heat emitter

The other most important feature is the emitter. If we are talking about a power flush, fit and leave type install, you will be going behind radiators that are sized based on an 80°C flow. A heat pump will not operate at this flow rate, so you have halved the temperature, which essentially halves the output. The customer is potentially left with a system that runs constantly and never reaches what they consider an acceptably warm temperature (for both heating and hot water). Then they see the eye-watering electric bill.

So, we should recommend refitting new, larger radiators or UFH to ensure that they meet the heat loss. If the suggested insulation listed above has been installed, the effect of heat loss is lowered. However, suppose the insulation isn’t suitable. In that case, bigger radiators will be needed, and the lower difference required between flow and return may mean that a new piping system will be required at an additional cost.

Replacement of existing rad’s (10 rad’s + avg. labour cost) £3500
Replace pipe system for 10 rad’s (£2000 excl. redecorating work.
Alternative fitting a UFH system (£7-8,000)

3. Can you straight swap a boiler to a heat pump?

The short answer (and most of us know) is No, due to these reasons.

Until the insulation, pipework and radiator sizes are addressed, the potential for heat pumps to work effectively in older properties is low. So, now for the scary bit. Suppose you do the right thing and quote around £25k to upgrade insulation, swap the emitters and install a suitable heat pump. In that case, you will be laughed at because no doubt less professional installers will say they can do the work for just over the cost of the available government grant. However, the homeowner will be left with an unfunctional system and high running bills and wishing they kept their old gas boiler.

Other Issues.

Running costs.

Ok, so after all this, because the efficiency of heat pumps is high (and they are!), you can look at around 400% efficiency, so for every kW of electric use, you get 4kW of heat energy. This will decrease the warmer you run a temperature, so keeping the flow temperature low is essential. But currently, electricity is four times the gas price, so there are no current running cost savings! Of course, the gas price will always rise, and we hope electricity will fall, but again this is another issue out of our control.

Winter problems.

The other thing to consider is basic physics. Heat pumps work by absorbing low energy outside the property and compressing it, amplifying its energy potential. This is great and super efficient during temperate days. But when the energy outside is low, the amplified energy is also low, so the unit works harder. So, your efficiency is not as good on very cold days (the days you need heating the most).