Derby Homes, the arm's length management organisation created by Derby City Council to manage, maintain and improve its social housing, has completed a heat pump retrofit at Rivermead House, a block of 54 flats. Each flat received its own Vaillant aroTHERM 5kW air source heat pump, a VRC 700 weather compensating system control and a 150-litre slimline hot water cylinder1. The work was published as a case study by Vaillant on 9 June 20221.
The flats were previously heated by electric storage heaters in an off-gas grid location, described as expensive and ageing1. Vaillant's team identified the balconies of each flat as the space to house the outdoor units1. The installation cost £6,000 per flat, which the case study describes as a 30 per cent saving against a comparable quote1.
Before the retrofit, average energy consumption of 13,068 kWh equated to costs of around £1,250 a year. With the heat pumps in place, bills have been reduced to £730 per annum, a typical saving of £520 a year per household1.
| Measure | Before | After |
|---|---|---|
| Heating system | Electric storage heaters | aroTHERM 5kW air source heat pump per flat |
| Average annual energy consumption | 13,068 kWh | Not reported |
| Typical annual cost | Around £1,250 | £730 |
| Typical annual saving | Not applicable | £520 per household |
| Installation cost per flat | Not applicable | £6,000 |
Derby Homes had initially considered a micro-district heat pump using energy from the ground or the local river, and wanted a solution that could be installed with as little disruption to tenants as possible at an affordable price1. The installation also means Derby Homes can take advantage of the domestic Renewable Heat Incentive (RHI)1.
"Thanks to Vaillant's help throughout the process, the feedback and support of the tenants has been excellent, there have been no problems whatsoever. The new heat pump systems are a major improvement on the electric storage heaters, and now the residents can enjoy affordable control of their heating throughout the entire flat"
Why it matters for households
Rivermead House is a worked example of what a heat pump retrofit looks like in a block of flats that has no gas connection, where the alternative to a heat pump is usually direct electric heating. The figures show the running cost gap that matters most to a household: the same homes moved from around £1,250 a year to £730 a year on the same kind of electricity supply, a difference of £5201. For a flat with storage heaters, that gap is the practical meaning of energy independence, because the household's exposure to electricity prices falls with the units it no longer wastes.
The £6,000 per flat figure is the capital cost side of the same calculation, and the case study presents it as 30 per cent below a comparable quote1. The design choice is also relevant to flats generally: each home got its own outdoor unit on its balcony rather than a shared ground or river source, which avoided the disruption of a district scheme1. What the case study does not report is how the £6,000 was funded, what tariff the £730 figure assumes, or how the flats are metered, so the split between landlord and tenant costs is not established.
What happens next
No next steps are set out in the case study. The domestic Renewable Heat Incentive is named as a scheme Derby Homes can take advantage of, but no application date, accreditation or payment figures are given1.
Sources1 cited
- Vaillant: Rivermead House - HPA UK, hpauk.org.uk