Heat-pump reality - part 1

Most homes will need to convert from fossil fuels to heat-pumps reduce CO2 in the atmosphere. What's actually involved?

Changing how people heat their homes is widely recognised to be one of the biggest challenges to meeting ambitious climate targets. The UK Government has an aspiration for 600,000 heat pumps to be installed per year by 2028, to replace other more carbon-intensive forms of heating. But what does an installation actually entail? We decided to 'walk the talk' and find out for ourselves.

The UK Government has an aspiration for 600,000 heat pumps to be installed per year by 2028, to replace other more carbon-intensive forms of heating.

We took advantage of the BEIS-funded Electrification of Heat Demonstration Project, which aims to demonstrate the feasibility of a large-scale roll-out of heat pumps. This project, delivered in Scotland by Warmworks (https://www.warmworks.co.uk/), installs the heat pump for free in exchange for provision of detailed data about its installation and operation over the first twelve months. Our heat pump was installed by an excellent team from Everwarm Group (https://www.everwarmgroup.com/), led by Dougie, Martin and Dave.

Before it all started…our main concerns were:

1. Whether our 1930s four-bedroom Edinburgh home was energy efficient enough to justify a heat pump

2. The upheaval during the installation, particularly whether we would have to lift our treasured hardwood floors

3. The impact of bigger radiators in our rooms and finding the space for the pump itself and the associated tank

4. The cost and feasibility of running a heat pump through the depths of a Scottish winter

5. The noise of the heat pump, both for us and for our next-door neighbours

The preparatory work involved two separate surveys, the first to check that we had a sufficiently insulated house to make a heat pump worthwhile. Like many homes that have been improved, we have an old part of the house – cold in winter because of only partially insulated (double) cavity walls and unlagged underfloor voids, partially rectified in the last few months with additional underfloor and loft insulation – and a new part, following a major extension 10 years ago, which is reasonably well insulated and also includes underfloor heating. Fortunately, overall, the house was reckoned to be OK for a large or hybrid (i.e. retaining the gas boiler) heat pump. As a result of the detailed heat loss calculations from the second survey, we were offered a 14kW Ecodan heatpump from Mitsubishi, which pleasingly is manufactured within 20 miles of us. OK, not as big as @Dave Pearson’s monsters – https://www.neatpumps.com/ – but size isn’t everything.

The installation took 3 (long) days from start to finish. The Everwarm team had to replace all our old, thin central heating pipes with lagged 22mm pipes, as well as replace radiators in all the rooms. Our big concern – that we would have to lift our beloved wooden floors – proved groundless. The excellent and ingenious Warmworks team managed to feed pipes underfloor to rooms with carpet – which they lifted along with a number of floor planks – to reach all the radiator positions. However, it still meant 3 days without hot water (warmth was not a problem with a mid-summer installation). We reckoned cold showers would be good for our student daughters who were home for the summer, but this might be a challenge for some families without an electric shower as a back-up.

Our big concern – that we would have to lift our beloved wooden floors – proved groundless. The excellent and ingenious Warmworks team managed to feed pipes underfloor to rooms with carpet.

While we had been concerned by the need for larger radiators, in practice, the size differential was not huge: occasionally a little wider, while double radiators became triple radiators and singles became doubles – adding 25-30mm to depth - and in one room, we had to add an additional radiator. With one exception – where we had to replace a designer radiator with a standard one in accordance with the BEIS project rules – the change of radiators has mostly been just a minor re-decoration issue. What was a surprise was the space needed for the 300l water tank, associated pipework and two header tanks indoors. We had ample space in a utility room, but not everyone will be so lucky.

So…the big question of cost! Obviously, under the BEIS scheme we were not forking out upfront for the cost. The contract works was for up to £12,500 worth of work (with the heat pump being priced at ~£10,000) which is more than most would commit to a heating system (though of course less than 5% of a typical house value). This compared with ~£2,500 to replace an old gas boiler at short notice last winter. Can we justify the additional £10,000? So far, hot water costs appear to be lower – noting that the heating has barely been on this summer – and we have just moved to the Octopus ‘Go’ tariff to take advantage of the 5p/kWh electricity price through the middle of the night. But we’ve not yet tested the pump properly through a cold winter, so the jury is still out – I’ll do an update in a year’s time.

Without a universal carbon price, and if financial payback was the only criteria, it would be difficult to justify the expense of a heat-pump without wider climate considerations and Renewable Heat Incentive payments. This will transform once heat pump prices reduce (which will happen over the next couple of years) and better heat pump tariffs are launched on the market (which will come). Our next obvious step is to integrate the heat-pump with solar panels – allowing self-use during the day and cheap overnight tariffs would appear an ideal way of minimising running costs.

And, finally, the noise…or rather, our lack of noticing the noise. The times we are in the garden tend to be on warmer days…when the heat pump is generally not being called by the system. Even when it is on in is surprisingly quiet. So, this element is less intrusive than we expected and certainly not loud enough to be noticed by our neighbours.

Overall, apart from a glitch with the heat pump itself (which Mitsubishi came out to fix), our experience has been positive to date: the system has delivered hot water when needed and promises a better-quality household warmth, more akin to the part of our house with underfloor heating, but we need to test our assumptions after a cold Edinburgh winter and once we return to working away from home through the day. More on that in Part 2... coming soon.