Commercial heat pump vs domestic: what changes at scale

Search for a commercial heat pump and many results look like domestic products at a bigger size. The refrigeration cycle is the same, but almost everything around it changes once a heat pump has to heat an office floor, a school block or a care home. This guide sets out what differs, so that a facilities manager can read a proposal with the right questions in hand. The delivery side is summarised on the commercial heat pump installation home page, and the two main system types have their own guides: commercial air source heat pump and commercial ground source heat pump.

The same cycle, a different job

All heat pumps use a refrigerant to move heat from a source (air, ground or water) to a heating circuit. A domestic unit heats one home, sized in single or low double figures of kilowatts, with one occupant group, one set of heating times and a hot water cylinder. A commercial system serves a building with several zones, different occupancy patterns, ventilation heat loads, large hot water draw in some sectors and, often, cooling demand as well. That raises the engineering effort on the design, not just the size of the box.

What changes at commercial scale

Capacity and cascades

Commercial capacity is usually assembled from several modular units rather than one large machine. A cascade gives resilience, because one unit can be serviced or can fail while the others carry most of the load, and efficiency, because units can be staged to follow the demand and run nearer their best operating point. It also suits phased installation, where part of the old plant stays live while the new plant is commissioned.

Electrical supply

A heat pump adds electrical load to a building that may have been heated by gas or oil. Larger units normally need a three-phase supply, and a substantial addition may require an application to the distribution network operator (DNO) and possibly a supply upgrade. Half-hourly meter data and the existing maximum demand show how much headroom the site has. Because a supply upgrade can take longer than the installation itself, the position is established at feasibility; the timings are covered in the guide on how long a commercial heat pump installation takes.

Heat-loss survey and consumption data

Commercial sizing starts from a room-by-room heat-loss calculation and at least twelve months of gas or oil consumption, checked against the coldest design day. Floor-area rules are unreliable because glazing, insulation, ventilation rates and occupancy differ widely between buildings. Over-sizing wastes capital and causes short cycling, while under-sizing leaves the building reliant on a boiler on cold days.

Emitters and flow temperature

Efficiency depends mainly on the flow temperature the heat pump must produce. Existing commercial buildings often have radiators, fan coils or air-handling coils designed for boiler temperatures. A survey shows which can run at a lower temperature and which need selective upgrades, a point explored in the guide on replacing radiators. Heat pump performance is declared as SCOP under BS EN 14825, using test points from BS EN 14511, and the figure that matters is the one at the building’s own design flow temperature.

Controls and the building management system

Domestic controls are simple: a thermostat and a weather-compensation curve. Commercial systems are integrated with a building management system (BMS) so that heating schedules, zone control, pump speeds, buffer temperatures and any retained boiler work together. Good commissioning proves that the controls deliver the design performance, not just that the plant runs.

Hot water and legionella

Where the system also supplies stored hot water, the building owner has duties to control legionella risk in water systems. The HSE’s Approved Code of Practice L8 sets the framework. Heat pumps that heat stored water to a lower temperature than a boiler need a design that deals with storage temperature, periodic higher-temperature cycles and risk assessment from the start.

Refrigerant rules

Refrigerants are regulated in the UK under the F-Gas Regulation, and handling them requires certified engineers. Routine leak checking and record keeping depend on the quantity of refrigerant in the equipment, which is larger in commercial plant. Propane (R290) is increasingly used because of its low global warming potential, but it is flammable, so BS EN 378 and a flammable-atmosphere risk assessment shape where the unit can go.

Noise and planning

External plant can disturb neighbours. A BS 4142 assessment compares the plant’s noise with the existing background level at the nearest sensitive receptor. The planning route depends on the site and should be confirmed with the local planning authority, with size, siting and noise conditions applying, while listed buildings and conservation areas need consent. Commercial sites are likely to have more complex surroundings than a house, which is one reason the acoustic position is settled before plant is ordered.

Funding and tax

The Boiler Upgrade Scheme covers non-domestic buildings as well as homes, but as a flat grant up to 45 kWth, so it only suits small systems; confirm eligibility with Ofgem. Commercial buyers of larger plant should look at capital allowances, which are covered on the capital allowances page, and check the status of any grant. Several schemes have closed; the current position is summarised on the grants and funding page, and ranges for cost are on the cost guide.

Domestic vs commercial at a glance

Factor	Domestic	Commercial
Typical capacity	One unit, small kW	Often several units in cascade
Electrical supply	Usually single-phase	Larger units three-phase; DNO check
Sizing basis	Room-by-room calculation	Heat-loss calculation plus 12 months of fuel data
Controls	Thermostat and compensation curve	BMS integration, staging, zone control
Hot water	Single cylinder	Possible large stored volumes and legionella duties
Grants	Boiler Upgrade Scheme (flat grant, up to 45 kWth)	Boiler Upgrade Scheme for small systems only; capital allowances
Noise and planning	Domestic permitted-development rules	Site-specific, BS 4142 assessment

What to ask a supplier

• How was the capacity calculated, and from what data?
• What is the design flow temperature, and what SCOP applies at it?
• What does the electrical supply need, and has the DNO been consulted?
• How will the controls integrate with the BMS?
• Which refrigerant is used, and what does that mean for siting?
• What will the acoustic assessment show at the nearest receptor?
• How is performance proved at commissioning?

Frequently asked questions

What is a commercial heat pump? A heat pump specified for a non-domestic building and sized from a heat-loss survey and real consumption data.

How is it different from a domestic one? Scale, supply, cascades, BMS controls, hot water duties and planning checks.

Does the Boiler Upgrade Scheme apply? Only to small systems: it covers non-domestic buildings up to 45 kWth.

Do they need three-phase power? Larger units normally do, and the DNO position is checked early.

Can a domestic unit be used in a commercial building? Only in very small premises; most need plant sized to a calculation.

To get a view on your own building, use the form below for a desk feasibility; the reply comes by email.