A broad introduction to heat sources, electricity use and the conditions that support good performance.
Core idea
An electrically driven heat pump moves heat from air, ground or water into a building. Its useful output combines heat taken from that source with an electrical contribution. Performance depends on source conditions and on the temperatures needed by the heating system.
What to recognise
- An air-source heating unit needs suitable airflow, noise assessment and provision for defrost.
- A ground-source system needs a suitable buried collector or borehole arrangement.
- Lower building heat loss and suitable emitters may allow a lower heating-water temperature.
- Design hot-water service, controls and any backup heat with the space-heating system.
- A COP value describes stated operating conditions; SCOP uses a defined reference season.
Apply it
Compare the building load, emitter temperatures, distribution, hot-water service, electrical supply and siting before selecting equipment. A nameplate heat output or a high seasonal rating does not establish whether the installation can meet the dwelling’s design heat loss.
Reading a seasonal rating
The seasonal coefficient of performance (SCOP) is calculated from reference heating demand and the electricity needed to meet it under standardised seasonal conditions. Compare like-for-like climate and temperature applications. It supports an annual estimate, but local weather, household demand and settings can differ from the reference assumptions. It does not directly specify the bill.
For an estimate, divide useful space-heating energy by the chosen seasonal ratio. A worked energy balance at a ratio of 3.5 is:
- Useful space heat: 3,150 kWh.
- Electrical input allowance: 3,150 ÷ 3.5 = 900 kWh.
- Heat collected from the source in the simplified balance: 3,150 − 900 = 2,250 kWh.
These are different parts of the same balance: adding one to the seasonal ratio would count the electrical contribution twice. Allow separately for domestic hot water, supplementary heating and any loads outside the estimate’s boundary. A measured seasonal performance factor uses recorded heat and electricity over a stated period; its result also depends on whether the meters include distribution pumps, backup heaters and storage losses.
Keep the boundary clear
The electric heat pump described here has no combustion stage. Electrical, pressure, refrigerant, water-hygiene and planning duties still apply. A system that includes a separate fuel-burning heat source also retains that appliance’s requirements. Use the actual survey, design and manufacturer information when making installation decisions.