Heat Pump Calculator — estimate heat pump for your project. Fast, accurate, free. No signup required.
Heat-pump sizing separates the building's peak heat demand from the machine's coefficient of performance. The electrical input is lower than the delivered heat when the COP is above one, but real seasonal performance depends on flow temperature, weather, defrost cycles, controls, and backup heat. The Heat Pump calculator keeps the topic-specific quantities visible so you can audit the assumptions before using the result.
Construction estimates are highly sensitive to site conditions, product specifications, local policy, and the stage of design. A useful early estimate states its units, boundary, design allowance, and source of any reference value. It should help you ask a better question of a supplier, designer, building-control officer, planning authority, or installer—not pretend that a three-field calculation is a signed design.
Use the related construction calculator for an adjacent check and the companion standards calculator when the result crosses into quantities, structure, services, energy, water, or regulation. Keep the original dimensions and assumptions with the displayed output so a later revision can be compared on like-for-like terms.
Where the page gives a consent, fire, electrical, accessibility, heritage, or safety prompt instead of a single number, that is deliberate. Those topics depend on documents, inspections, local rules, tested products, and professional judgement. The calculator can organise the first pass, but it cannot issue an approval or replace a competent person's review.
Electrical input (kW) = design heat demand (kW) ÷ COP; annual electricity (kWh) ≈ electrical input × equivalent full-load heating hours.
The formula is intentionally shown beside the inputs. Convert millimetres, metres, kilowatts, amps, percentages, and category scores consistently, and keep intermediate precision until the final display. A plausible-looking answer can still be unusable if a clear opening was confused with an outside frame, a nominal capacity with a tested rating, or a planning assumption with a statutory threshold.
For site work, the formula is the beginning of the check rather than the complete specification. Add the conditions that control the real decision: subgrade and drainage for roads, grouping and installation method for cables, weather and emitter temperature for heat pumps, significance for heritage, occupancy for escape, and local policy for planning matters.
Inputs used here: design heat demand, heat-pump COP, and annual heating hours. Keep each input traceable to a drawing, survey, test result, product sheet, policy document, or clearly marked planning assumption.
The output is an early-stage comparison of electrical input and running cost. A room-by-room heat-loss calculation and a seasonal COP or SCOP from the proposed product are needed before selecting equipment or radiators.
Check direction and order of magnitude before relying on the result. A larger opening should increase area, a longer cable should increase voltage drop, a higher COP should reduce electrical input, a wider exit should increase the indicative capacity, and a higher traffic class should demand a stronger cover or pavement solution. If a change behaves the other way, recheck the units and the field mapping.
Do not report more precision than the survey or input supports. Round a procurement quantity up where the supplier sells discrete sizes, preserve the unrounded design calculation for review, and label any result based on a default rate or simplified weighting. If the number affects structural stability, fire safety, electric shock protection, accessibility, legal consent, or a regulated rating, stop at the estimate and obtain the appropriate review.
Heat-pump design, refrigerant work, electrical supply, and commissioning require appropriately qualified installers and current manufacturer data. This calculator provides preliminary educational guidance only and does not constitute a structural design, electrical certificate, fire strategy, planning decision, Building Regulations approval, heritage consent, accessibility audit, or certified sustainability assessment.