Specification options: Ground-source heat pumps
 Capital costLifecycle cost Expected service life
Domestic scale: 4–8kW heat output   
Horizontal pipework laid in trenches650–1,0501,18050–100
Horizontal looped (slinky) pipework laid flat in trenches730–1,1301,36050–100
Vertical pipework in boreholes700–9501,30050–100
Heat pump 4–8kW heat output800–1,0002,19015–25
Commercial scale: 30–50kW heat output   
Horizontal pipework laid in trenches625–1,0251,08050–100
Horizontal looped (slinky) pipework laid flat in trenches700–1,1001,24050–100
Vertical pipework in boreholes1,080–1,4801,71050–100
Heat pump 30–50kW heat output650–8001,79015–25
Table notes A discount rate of 3% is used to calculate values. Lifecycle costs are indicative and are based on the average of capital costs and service lives. Lifecycle cost for pipework allows for a probability of pipe failure and costs associated with the circulation pump. Costs in use include inspection, servicing, allowance for responsive maintenance. Distribution side costs and energy costs are excluded. Pipework is a closed loop system of HDPE to relevant British Standards. Heat pump to British Standards noted in text. Pipework costs will vary with nature of soil and heating demand of building. Number and depth of boreholes and degree of grouting will influence cost. Economies of scale may apply to larger developments. A cost analysis based on project specific information is essential for a realistic appraisal.