A managed heating service designed to support EPC C outcomes in retrofitted rental properties.
For years, the way the UK measures building energy performance has quietly penalised direct electric heating. Not because electric heating is inefficient, but because the EPC calculation is dominated by a fixed assumption that electricity costs around 3.8× as much per unit as mains gas. That single assumption has held back the electrification of heat and left millions of homes, especially older, hard-to-treat and privately rented properties, unable to reach the EPC ratings now demanded by regulation.
Under SAP 10.2 / RdSAP 10 the standardised prices are approximately 3.5 p/kWh for mains gas and approximately 13.2 p/kWh for electricity. So electricity is treated as around 3.8× more expensive per unit. No matter how efficient or controllable a direct electric system is in the real home, the EPC will score it far below gas.
Take a 100 m² semi-detached house with identical fabric, hot water and lighting, changing only the heating system:
| Heating system (same house) | SAP score | EPC band |
|---|---|---|
| Gas boiler + radiators | ≈60 | D |
| Conventional electric underfloor heating | ≈25 | F |
A second penalty compounds it. SAP applies a responsiveness multiplier from 1.0 (fast, direct-acting emitters such as radiators) down to 0.25 (very slow systems). Conventional electric underfloor heating is treated as the slowest category, on the assumption it takes 4–5 hours to lift a room by 3°C, so it is penalised twice: once on fuel price, and again on responsiveness. JustHeat® has been shown to take only 1 hour to lift a room by 3°C.
None of this reflects how JustHeat® actually performs.
Direct electric heating converts essentially 100% of the electricity it draws into heat at the point of use. There is no flue loss, no standing pilot and no distribution loss.
The UK grid has decarbonised faster than almost any other sector, so electricity is now far cleaner per kWh than when these assumptions were set. The carbon case for electric heat is the opposite of what the fuel-price metric implies.
Independent measurement shows JustHeat® raising a floor from 16°C to 28°C in 17 minutes and delivering a 3°C room lift within the hour, squarely in the fast, direct-acting category alongside radiators.
The historic EPC penalty on electric heating is an artefact of an outdated cost metric, not a reflection of real-world performance. This is a point the Government’s own EPC reform programme is now moving to address, by shifting emphasis away from fuel cost and towards carbon and fabric performance.
A decisive change does not require every property to wait for EPC reform. It comes from how the EPC calculation treats heat that is delivered as a service. Under the EPC calculation it is not the physical infrastructure (pipes, central plant) that determines the heating category, it is who owns the heating generator.
JustHeat® is now available as a delivered Heat-as-a-Service installation: the service provider owns the heat generator, and the landlord enters into a Heat-as-a-Service agreement. Under the HaaS convention, JustHeat® electricity is no longer priced at the 13.2 p/kWh direct-electric rate in the calculation, but at a rate of 4.24 p/kWh (× distribution-loss factor). This addresses the punitive standard electricity price built into the EPC calculation.
The Heat-as-a-Service convention removes that barrier for JustHeat®. Under the convention, JustHeat® moves hard-to-treat homes up to three EPC bands, delivers MEES Band C in realistic retrofits, and can match or beat the standard SAP heat pump without the cost and disruption of a heat pump installation. JustHeat® is a compliant, forward-looking, low-capital-cost heating solution, and under the Heat-as-a-Service convention the framework finally recognises it as one.
Independent SAP modelling by Quidos compared JustHeat® under the HaaS convention against the full range of heating systems, across dwelling archetypes (small, medium, large, extra-large and apartments), construction ages (pre-1900, 1970s and new) and fabric states (uninsulated, and insulated with solar PV).
In older, uninsulated properties, exactly the stock that fails EPC requirements today, replacing electric panel heaters with JustHeat® under the convention lifts the rating by up to three bands:
| Archetype (uninsulated, pre-1900) | Electric panel heaters | JustHeat® (HaaS) | Improvement |
|---|---|---|---|
| Small house (50 m²) | F (28) | D (56) | +2 bands |
| Medium house (80 m²) | G (17) | E (50) | +2 bands |
| Large bungalow (150 m²) | G (20) | D (55) | +3 bands |
| Extra-large house (225 m²) | G (20) | D (57) | +3 bands |
| Apartment (50 m²) | D (56) | C (71) | +1 band |
JustHeat® outperforms every other direct electric option (panel heaters, direct-acting electric boilers and electric storage heaters) across these scenarios.
When JustHeat® is installed as part of a sensible retrofit (insulation plus solar PV), it reaches band C or B in every archetype tested, clearing the MEES threshold, and matches or beats the standard SAP heat pump assumption in the majority of cases:
| Archetype (insulated + PV, pre-1900) | Electric panel | Heat pump (SAP) | JustHeat® (HaaS) |
|---|---|---|---|
| Small house (50 m²) | D (66) | B (82) | B (82) |
| Medium house (80 m²) | D (57) | C (76) | C (80) |
| Large bungalow (150 m²) | D (64) | C (80) | B (85) |
| Extra-large house (225 m²) | D (60) | C (77) | B (83) |
| Apartment (50 m²) | C (79) | B (88) | B (85) |
In four of these five retrofit archetypes JustHeat® equals or exceeds the standard SAP heat pump, and it does so without the capital outlay, external plant, refrigerant servicing or installation disruption of a heat pump retrofit. This heat-pump-matching performance is characteristic of the older house stock (pre-1900 and 1970s houses and bungalows) that dominates the retrofit and private-rented markets.
Two systems can still score above JustHeat® in the EPC model: mains gas boilers, and manufacturer-listed (PCDB) heat pumps, typically by around one band. This is expected, as the calculation still rewards the very low standardised price of gas, and database-listed heat pumps carry verified high seasonal efficiencies. But the comparison that matters in practice is against the direct electric heating in millions of flats and hard-to-treat homes, where JustHeat® wins decisively, and against the real-world cost and disruption of ripping out and replacing a heating system with a heat pump.