Ground Source Heat Pump Calculator

Sizing, ground array, SCOP, running cost & fuel comparison

Territory

ðŸ‡¬ðŸ‡§ UK & Ireland

ðŸ‡ªðŸ‡º Europe

ðŸ‡ºðŸ‡¸ USA & Canada

ðŸ‡¦ðŸ‡º Aus & NZ

ðŸŒ Other

Region

★ Ground temp: ~10°C · 1,600 full-load hrs/yr

Property Type

Detached

Semi-detached

Terraced

Flat

Bungalow

Total Floor Area (m²) Total heated floor area across all storeys.

Insulation Standard

Poor (pre-1940s)

Average (1980s-2000)

Good (post-2000)

Excellent (EnerPHit)

■ Enter floor area to estimate heat loss

Use manual heat loss value

Ground Collector Type

ðŸŒ¿

Horizontal loops

Buried 1-2 m deep in trenches. Needs large garden area.

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Vertical boreholes

Drilled 50-150 m deep. Minimal surface area needed.

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Slinky loops

Coiled pipe in trenches. Less land than straight horizontal.

■ Enter floor area to estimate ground array

Heat Distribution System

Underfloor heating (35°C)

Upgraded / large radiators (45°C)

Standard radiators (55°C)

★ Est. SCOP: 4.2

Tariffs & Costs

Electricity rate (p/kWh) Unit rate from your energy bill

System cost (optional) Full installed cost including ground works. Used to calculate payback.

Current Fuel Comparison

Existing fuel type

Gas

Oil

LPG

Electric

None

Fuel rate (p/kWh) Mains natural gas boiler - check your bill for exact rate

Ground Source Heat Pump Results

SCOP by Flow Temperature

GSHPs achieve higher SCOP than air source because ground temperature is stable year-round. Values shown for moderate ground temperature (~10°C).

Flow temp	Cold (<7°C)	Moderate	Warm (>14°C)
35°C (UFH)	3.6	4.2	4.8
45°C (large rads)	3.0	3.5	4.0
55°C (std rads)	2.5	2.9	3.3

GSHP SCOPs are typically 20-30% higher than ASHP for the same flow temperature, due to stable ground temperature.

Ground Array Guide

Collector type	Extraction
Horizontal loops	~20 W/m²
Buried 1.2-2 m deep. Needs ~15-25 m² per kW of heat loss.
Vertical boreholes	~55 W/m
Drilled 50-150 m deep. Typically 18-20 m per kW. Boreholes spaced 5-6 m apart.
Slinky loops	~30 W/m²
Coiled pipe in trenches. ~10-15 m² per kW - more compact than straight horizontal.

Actual extraction rates vary with soil type (clay > sandy soil), moisture, and depth. A ground survey is recommended before installation.

Heat Loss Guide

Insulation	W/m²
Poor (pre-1940s)	115
Average (1980s-2000)	80
Good (post-2000)	50
Excellent (EnerPHit)	22

GSHP pairs best with well-insulated fabric - reducing heat loss also reduces the ground array size required.

Key Terms

SCOP - Seasonal COP: average efficiency over the heating season. A SCOP of 4.0 means 4 kWh of heat per 1 kWh of electricity.
Ground temperature - Below ~2 m depth, ground temperature is stable year-round (typically 8-12°C in the UK). Warmer ground = higher SCOP.
Full-load hours - Equivalent hours per year at design output. Multiplied by heat loss to give annual heat demand.
MCS - Microgeneration Certification Scheme. Required for UK grant eligibility (Boiler Upgrade Scheme - £7,500 for GSHP).
Borehole spacing - Vertical boreholes must be 5-6 m apart to avoid thermal interference. Factor this into available land area.

Ground Source Heat Pump Calculator