Commercial heat pump savings: how to estimate them

The one-line method

Annual saving = what the existing heating costs for a year, minus what the heat pump would cost to run for the same heat. Three numbers drive it: the heat the building uses, the heat pump's seasonal efficiency (SCOP), and the price of the fuel and electricity involved.

Step 1: the heat the building uses

Start from at least twelve months of gas or oil consumption, not floor area. Convert the fuel used into delivered heat by allowing for the boiler's efficiency. Floor-area rules of thumb miss glazing, occupancy hours and fabric quality, which is why a good installer asks for consumption data and carries out a heat-loss survey before quoting.

Step 2: the electricity the heat pump will draw

Divide the heat needed by the SCOP. A SCOP of 3 means three units of heat for each unit of electricity over a year. SCOP falls as the flow temperature the heating system needs rises, so a building with old, small radiators may need emitter upgrades before the numbers work. Ask the installer which SCOP they assumed and at what flow temperature.

Step 3: price both sides

Multiply the electricity by your unit rate, and the fuel saved by your fuel rate. Use your own current tariffs, including standing charges and any change to the electricity supply capacity the project needs. Check the sums with a range of prices, because the saving depends on the gap between electricity and fuel prices as much as on the heat pump.

A hypothetical illustration

These numbers are made up to show the arithmetic and are not market prices. Suppose a building needs 400,000 kWh of heat a year, the heat pump achieves a SCOP of 3, electricity costs 25p a kWh and the existing boiler system costs 7p for each kWh of heat delivered. The heat pump draws about 133,000 kWh of electricity, costing roughly £33,000, against £28,000 for the existing system. In that case there is no running-cost saving at all, which is why the price gap and the SCOP matter, and why grants and carbon savings are often part of the case instead. Change the SCOP to 4 and the same building draws 100,000 kWh costing £25,000, a saving of £3,000 a year.

What else changes the answer

• Capital cost, and any grant that reduces it. See the grants and funding guide and the cost guide.
• Maintenance, refrigerant and controls costs over the life of the system.
• Hybrid designs that keep a boiler for the coldest days, covered on the hybrid retrofit page.
• Tax treatment of the spend, which you should confirm with an accountant.

Questions

How is the annual running-cost saving calculated?

Take the heat the building uses in a year, divide it by the heat pump's seasonal coefficient of performance (SCOP) to get the electricity it will draw, price that electricity, and compare it with what the existing gas or oil heating costs for the same heat. The gap is the running-cost saving before any maintenance or tariff changes.

Why do two similar buildings get different savings?

Heat demand, the flow temperature the emitters need, the electricity tariff, the fuel being replaced and the boiler efficiency all change the answer. A building that needs high flow temperatures lowers the SCOP and the saving.

Is this page a quote?

No. This page explains the method only. A real figure needs the building's heat demand and a survey carried out by an installer. If you send an enquiry, we reply by email.