Commercial Air Source Heat Pump: Sizing, SCOP and Cost

Searches for a commercial air source heat pump usually come from someone with a boiler that is close to the end of its life and a deadline. The questions are practical: how big does it need to be, how efficient will it really be, what does it cost and what can go wrong. This guide answers them in the order a facilities or estates manager meets them, using the published standards and the figures that hold across UK commercial buildings.

What counts as a commercial air source heat pump

A commercial air source heat pump extracts heat from outside air and delivers it to a wet heating system at a scale that a domestic unit cannot reach. In practice the range runs from about 40 kW thermal for a small office or shop up to around 500 kW thermal for a large care home, school or light industrial unit, supplied either as one machine or as a cascaded bank of modular units. Above that, ground-source, high-temperature or heat-network designs usually enter the comparison, and our air source versus ground source guide sets out where the line falls.

The distinction from a domestic unit matters for money as well as engineering. The £7,500 Boiler Upgrade Scheme is domestic-only and does not apply to a commercial building, so the funding conversation starts somewhere else entirely, covered in the funding section below.

How a commercial air source heat pump is sized

Sizing from floor area is the classic way to get a commercial heat pump wrong. Two buildings of the same size can need very different plant: a care home runs flat out all year with constant hot water, while a school sits dark through the holidays. The right inputs are a proper heat-loss survey and at least twelve months of gas or oil consumption, ideally with half-hourly meter data so the shape of demand is visible and not just the total.

Sizing also decides how the plant behaves in the shoulder seasons. A single large unit forced to modulate down to a small summer hot-water load runs inefficiently and wears quickly. A cascade of modular units can bring one machine on for a light load and the whole bank on for the depths of winter, so the system spends most of the year near its efficient operating point. A typical cascade is anywhere from a single unit to a bank of 4 to 12 modules, and the plant area it needs ranges from roughly 20 to 200 square metres depending on the capacity.

The buffer vessel arrangement, the controls and weather compensation deserve the same attention as the heat pump itself. These hold the flow temperature down in real operation instead of only on paper, and a system that is correctly sized but left to run at a fixed high flow temperature will never deliver its rated efficiency.

SCOP: the number that decides your running cost

SCOP, the Seasonal Coefficient of Performance, is the average heat delivered divided by the electricity used across a whole heating season, measured to BS EN 14825. An SCOP of 3.5 means 3.5 units of heat for every unit of electricity. Rated COP, measured to BS EN 14511, is a point-in-time figure under set conditions and flatters the machine, so when comparing quotes ask which figure is being quoted and to which standard.

For commercial air source systems an SCOP of roughly 3.0 to 4.0 is the range to expect. Where in that range a building lands depends mostly on flow temperature. Designing for 45 to 55C, wherever the emitters allow, lifts the SCOP; every degree shed improves the efficiency for the life of the plant. That is why a sound assessment surveys the existing radiators, fan coils and pipework before pricing anything, and why a quote that skips the emitter survey is a warning sign.

Electricity costs more per unit than gas, so the SCOP is what determines whether the system saves money. At 3.0 to 4.0, a well-designed system offsets most of that unit-price gap, and the comparison improves as gas carbon costs rise and the grid decarbonises. The honest way to settle it for one building is a model built from its own consumption at current and forecast prices, which is exactly what a free desk feasibility from meter data produces.

What it costs and how long it takes to pay back

A commercial air source project typically runs from about £60,000 to £600,000 installed, with a simple payback around 8 years on a well-matched building. The spread comes from capacity, the emitter upgrades the flow temperature requires, whether a supply upgrade is needed from the distribution network operator (DNO), the siting of the plant and the controls package. Our commercial heat pump cost guide works through the figures by system type, and the cost and payback article shows how the payback is built up.

Tax treatment is the largest single lever. Heat pumps qualify as plant and machinery, so a company paying corporation tax can claim full expensing, a 100% first-year deduction with no cap that became permanent from April 2026, worth up to 25p of tax saved for every pound spent at the 25% rate. Unincorporated businesses use the Annual Investment Allowance instead, up to one million pounds of qualifying spend at 100%. Some wiring and ancillary works can fall outside full expensing but usually qualify for the allowance, and the exact treatment should always be confirmed with an accountant.

Grants: what has closed and what is left

Commercial grant support has narrowed. The Public Sector Decarbonisation Scheme has had no open application window since Phase 4 closed in November 2024, and gov.uk lists no further phase. The Industrial Energy Transformation Fund closed in July 2025 and gov.uk states that no successor fund is planned. The Green Heat Network Fund runs in application rounds: Round 12 closed on 25 September 2026, so check gov.uk for the next round. For a single-building private sector job that leaves capital allowances as the dependable relief, which is why the sequence is design, tax position, then any grant that happens to be open, never the other way round. Current status for each scheme is on our grants and funding page.

Siting, noise and planning

Noise is the point that catches the most projects out. Many commercial air source installations fall under permitted development, but they are subject to siting and noise limits, so a BS 4142 acoustic assessment is commonly needed to show the external units will not disturb neighbours. Listed buildings and conservation areas need consent. The plant compound or roof deck also has to allow airflow and safe maintenance access: a unit starved of air, or packed tight against a wall, loses efficiency and is awkward to service.

Electrical supply and refrigerants

A large air source bank adds meaningful electrical load, so available supply capacity should be confirmed with the DNO at the start. A supply upgrade, and any G99 paperwork for generation on the same site, can be the longest-lead item in the whole project, which is why it is checked before the design is fixed and not after.

Refrigerant work must be carried out by F-Gas certified engineers under the UK F-Gas Regulation. Modern units increasingly use lower global-warming-potential refrigerants such as R32 as the phase-down of high-GWP gases bites, while natural refrigerants such as R290 (propane), CO2 and ammonia are used for high-temperature duties and carry their own siting and safety requirements, including DSEAR and ATEX considerations for flammable gases.

When an air source heat pump is the wrong answer

Air source is the default starting point because it needs no ground works and is the quickest route from survey to a working system, but it is not right everywhere. Buildings with stubborn high-temperature radiators may suit a hybrid design that sizes the heat pump for roughly 70 to 90% of annual load and keeps a boiler for the coldest days. Year-round buildings with land available may repay the higher capital of ground source, and genuine process-heat duties belong with high-temperature and industrial heat pumps. Sometimes the honest answer is to improve the fabric first.

A checklist before you buy

• Sizing based on a heat-loss survey and twelve months of consumption, not floor area.
• SCOP quoted to BS EN 14825, with the design flow temperature stated.
• An emitter and pipework survey before the price is fixed.
• A BS 4142 acoustic assessment where neighbours are close.
• DNO supply capacity checked early, with any G99 work identified.
• Proof of MCS certification for systems up to 45 kWth and F-Gas certification for refrigerant work, checked against the issuing bodies.
• An itemised proposal that shows the running-cost model, so it can be stress-tested or taken for a second opinion.

If you want those questions answered for a specific building, the free desk feasibility request takes meter data and returns a plain assessment with no obligation. The wider picture for each technology sits on the commercial air source heat pump guide.

Frequently asked questions

What size commercial air source heat pump do I need?

It depends on the building heat loss and the shape of demand, not on floor area. A heat-loss survey and at least twelve months of gas or oil consumption, ideally with half-hourly meter data, give the peak and annual heat demand that the plant is sized against. Typical commercial systems run from about 40 to 500 kW thermal.

What is a good SCOP for a commercial air source heat pump?

Roughly 3.0 to 4.0 across a heating season is the expected range, measured to BS EN 14825. The main driver is flow temperature: designing for 45 to 55C wherever the emitters allow lifts the figure.

Do I need planning permission for a commercial air source heat pump?

Many commercial installations fall under permitted development, subject to siting and noise limits, and a BS 4142 acoustic assessment is commonly needed. Listed buildings and conservation areas need consent. Check with the local planning authority for the specific site.

Is the Boiler Upgrade Scheme available for a commercial building?

No. The Boiler Upgrade Scheme is for domestic properties. Commercial buildings rely on capital allowances such as full expensing or the Annual Investment Allowance, plus any grant scheme that is open at the time.