Retrofit Boreholes for Social Housing Flats

This section illustrates the costs of replacing the heating and hot water systems in 60 social housing flats with Kensa ground source heat pumps. The scheme features an individual Kensa Shoebox Heat Pump in each flat, connected to a Shared Ground Loop Array of boreholes.

We have provided a ground source heat pump design with schematic drawings and ground source heat pump installation costs for both self-financed and funded split ownership shared ground loop array options versus an electric night storage heater (NSH) alternative.

Ground Source Review Chestnut Mews & Aspen Mews ǀ During Installations

Example: Finances

Kensa has calculated example costs below to illustrate the upfront finance required for self-financed and funded split ownership Shared Ground Loop Arrays in a typical retrofit housing development featuring the Kensa Shoebox heat pump.

For a bespoke quote, please click here.

Heat Pump System

System architectureShared Ground Loop Arrays
Total heat pump capacity191.56 kW
Equipment type30 x 3kW Shoebox & 30 x 6kW Shoebox
Design conditions0/50°C
Potable DHW temp60°C
Integral immersion heatersNo (DNO friendly)
Ground array typeBoreholes
Total depth of boreholes3,853 metres
*Boreholes based on average ground conductivity. Average 18 sq/m per property – each borehole serves a minimum of 2 properties.


Total Project Costs, Savings & Returns vs Electric NSH

Kensa Ground Source Heat Pumps & Shared Borehole Ground Array

Electric NSH
Finance OptionSelf-FinancedFunded Split OwnershipSelf-Financed
Lifetime Expectancy: ApplianceUp to 20 yearsUp to 20 yearsUp to 10 years
Lifetime Expectancy: InfrastructureUp to 100 yearsUp to 100 years-
Carbon Saved vs. NSH (over 20 years)*5,381 TCO²5,381 TCO²-
Local NOx Emissions Saved**19.6 kgNOx/y19.6 kgNOx/y19.6 kgNOx/y
Appliance, Infrastructure & Project Management Cost ^£698,500£323,101£189,000
Running Cost Savings vs. NSH (over 20 years)***£484,045£484,045-
Servicing Costs Per Property (over 20 years)****£2,000£2,000£2,000
ECO Funding Contribution£53,805£53,805Not eligible
RHI Income (over 20 years)*****£931,134-Not eligible
Net cost (after 20 years)******£286,439 profit£269,296 cost£189,000 cost
*Carbon saving based on carbon emissions of 0.519kgCO2/kWh for electric. Assumes 100% efficiency for electric and 300% efficiency for ground source heat pumps. **NOx emission based on 44mg per kWh based on a worcester greenstar combi. ***Based on electric at 15p/kW/hr and COP of 3. ****Ground source heat pumps have no requirement for annual maintenance. However, it is good practice for the heating distribution system to be proactively checked and maintained to ensure optimum performance G3 Cylinder check will be requried. *****The Non-Domestic RHI is a 20 year index linked funding stream which assumes inflation at 3%. ******Net cost does not include servicing and running costs. ^ Retrofit costs include internal fit out i.e. new radiator systems. Tenant network connection fee applies.
Please note: The Non-Domestic RHI has now ended. Visit Kensa Heat Pumps to explore current funding options.

Example: Capex

Cumulative Deficit / Surplus Over 20 Year RHI Period

social retrofit flats capex graph

Counterfactual based on electric NSH costs
Please note: The Non-Domestic RHI has now ended. Visit Kensa Heat Pumps to explore current funding options.
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