Landlord heat pump glossary
- Air-to-air heat pump
- A heat pump that moves heat between outdoor air and indoor units that blow warm or cool air into rooms. It does not feed radiators or heat hot water. The Boiler Upgrade Scheme pays £2,500 towards one in a home, replacing existing heating. More
- Air-to-water heat pump
- The usual domestic heat pump: it takes heat from outdoor air and feeds a wet system of radiators or underfloor heating and a hot water cylinder. Also called an air source heat pump (ASHP). More
- Ambient loop
- A low-temperature shared pipe loop that several buildings or flats tap with their own small heat pumps. Used on larger developments and build-to-rent blocks. More
- Assured shorthold tenancy (AST)
- The standard private tenancy before 1 May 2026. Under the Renters' Rights Act almost every tenancy in England converted to a periodic assured tenancy on that date. More
- Boiler Upgrade Scheme (BUS)
- A government grant towards a heat pump or biomass boiler for property owners in England and Wales, including landlords: £7,500 for an air-to-water or ground source heat pump, £9,000 where oil or LPG is replaced in a home with no mains gas connection until 31 March 2027. More
- Cost cap
- The most a landlord is planned to be required to spend per property to reach EPC C: £10,000, counting qualifying work since 1 October 2025. Today's cap under the existing rules is £3,500 (including VAT). More
- Dual-metric standard
- The planned EPC C approach: a fabric performance standard first, then the landlord chooses to meet either a heating-system standard or a smart-readiness standard. More
- EER (Energy Efficiency Rating)
- The cost-based score and A to G band shown on an existing EPC. The English Housing Survey reports on homes by their EER band.
- EPC (Energy Performance Certificate)
- A certificate rating a property from A (most efficient) to G, valid for ten years. A property needs one to be let. More
- ECO4
- The fourth Energy Company Obligation, a supplier-funded scheme for low-income and vulnerable households, closing 31 December 2026. More
- Exemption
- A registered reason a landlord can keep letting below the required EPC band. Under the planned rules, spending the £10,000 cap without reaching C gives a 10-year exemption; under today's rules most exemptions last 5 years. More
- Fabric first
- The approach of improving insulation and airtightness before changing the heating system, because a better-insulated home needs less heat and a smaller, cheaper, more efficient heat pump. More
- Ground source heat pump (GSHP)
- A heat pump that takes heat from pipes buried in the ground or a borehole. Also grant-funded at £7,500, but the groundwork costs more and needs outdoor space.
- HMO (house in multiple occupation)
- A property let to several tenants who share facilities. HMOs have extra licensing and safety duties and are a harder fit for a heat pump because of shared systems and many separate tenancies. More
- Hybrid heat pump
- A heat pump working alongside a gas boiler. The Boiler Upgrade Scheme does not fund hybrid systems. More
- kWth
- Kilowatts of thermal output: the size of a heat pump's heat output. The Boiler Upgrade Scheme covers up to 45kWth for a single installation.
- MCS (Microgeneration Certification Scheme)
- The certification body for small-scale low-carbon installers. A heat pump installer claiming the Boiler Upgrade Scheme grant must be MCS-certified. More
- MEES (Minimum Energy Efficiency Standards)
- The rules on the energy performance of rented property. The legal minimum today is band E; the government plans EPC C by 1 October 2030. More
- PRS (private rented sector)
- Homes let by private landlords, as opposed to social housing let by councils and housing associations.
- Renters' Rights Act
- The 2025 Act that abolished section 21 no-fault evictions and converted most tenancies to periodic assured tenancies from 1 May 2026, with a landlord database and ombudsman to follow. More
- SCOP (seasonal coefficient of performance)
- How many units of heat a heat pump delivers for each unit of electricity over a heating season. A SCOP of 3.5 means 3.5kWh of heat per 1kWh of electricity. The Boiler Upgrade Scheme minimum for air-to-water is 2.8. More
- Smart readiness
- One of the two planned second-step options in the EPC C standard: measures that let a home use energy flexibly, such as smart controls.
- Tenant in situ
- A tenant already living in the property. It affects when and how work can be done. More
- TrustMark
- The government-endorsed quality scheme for trades, with a public register you can check. More
- Warm Homes: Local Grant (WH:LG)
- A council-delivered grant in England for lower-income households in homes rated EPC D to G. A landlord's first property can be fully funded; from the second property the landlord contributes 50%. Greater Manchester and West Midlands combined authority areas (including Manchester, Birmingham and Coventry) are outside the national scheme and set their own landlord terms. More
- Warm Homes Loan Scheme
- A lender-provided loan, open to owner-occupiers and private landlords, with government support so lenders can offer a lower rate. More
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