Mark Hall

How well does a heat pump work in an old house?

After 5 years of learning from the best I designed and installed my first Air Source Heat pump with a full heating system. After living with it in our 300 year old home for over a year and a half I’m blown away with how well it works. The cheapest and best way to heat our home.

Constantly warm in every room and a full year- whole house energy bill of £1547 for heating, hot water, cooking, washing and every thing else. No solar, no battery. That’s a family of 4 in a 5 bedroom historic house (250m2) with predominantly solid wall construction. (Note- Partial year on the OVO heat pump tariff and partial year on a standard rate tariff).

2025 full year SCOP shown as 5.6 (note that comparing Viessmann SCOP with independently monitored Viessmann performances - real world SCOP likely to 4.6-5.6). That’s at least 460% efficiency over the year for heating and hot water.

From July, a £9000 grant is available when replacing an oil boiler (or LPG boiler). £7500 for a Natural Gas boiler or direct electric heating replacement. I would almost always install a heat pump system on a full renovation like this or a new build. Retro fit can be more of a challenge but the vast majority of UK homes are suitable.

What about the installation cost? Renewable installs are no VAT so that’s 20% saved on all the materials and labour. With the £7500 BUS grant I received I estimate it was £2500 cheaper than an oil heating system or £4500 cheaper if a new oil tank and trenching to be installed. I think it would be a similar cost to a new Natural Gas boiler and system of this size, but you have VAT saving.

The plant room area was a luxury space to work in- most systems only need an airing cupboard inside.

The system is future proof and running costs could reduce even further if we get solar and or batteries.

Thanks to @damon_bphr for the MCS, commission day and technical phone support when installing the kit for the first time.
@osohotwateruk @viessmanncsglobal @esbeltd @heatinginstallerawards @renewableheatinghub @heat_geek @warmur_academy @installd.uk @allsaltsplumbing water softener