Heat pumps and commercial EPCs: the benefits of Level 5 DSM modelling

A heat pump transfers heat from air, ground or water rather than producing all its useful heat by burning fuel. Its coefficient of performance (COP) describes heat output divided by electrical input at specified operating conditions. A COP of 3 means three units of useful heat for each unit of electricity at those conditions; it is an illustration, not a guaranteed annual result.

The International Energy Agency’s explanation of heat pumps sets out that principle. For investment decisions, distinguish a test-point COP from seasonal performance and from whole-system consumption, which can also include circulation pumps, fans, controls and backup heaters.

Replacing combustion-based heating with a well-designed electric heat pump can reduce heating-related carbon emissions. The scale depends on the fuel displaced, seasonal efficiency and electricity emissions. There is no combustion at the heat pump itself, but electricity generation and refrigerant leakage still have environmental impacts: it should not be described as automatically zero-carbon heating.

Some reversible systems provide both heating and cooling, which can simplify a building’s plant strategy. That does not mean every heat pump also provides domestic hot water, or that cooling is free. Check the selected equipment, ventilation needs and hot-water duties separately, particularly where higher temperatures or hygiene controls are required.

Lower-temperature heating can support steady comfort when emitters and controls are designed for it. Running costs may fall, especially compared with direct electric heating, but savings against gas depend on tariffs, achieved seasonal efficiency, maintenance and electrical capacity charges. Electrification changes exposure to fuel prices; it does not remove electricity-price risk.

A non-domestic EPC is a modelled asset rating based on calculated carbon emissions under standardised use. Heating efficiency and fuel type contribute to that calculation, alongside cooling, ventilation, lighting, fabric and eligible on-site generation. It is not an assessment of the current occupier’s utility bills.

A correctly represented heat pump can reduce calculated emissions compared with the baseline plant and therefore improve the numerical EPC score. Whether that crosses a band boundary depends on the starting score and the contribution of heating to the building’s overall result. A heavily lit or mechanically ventilated building may need other improvements as well.

Domestic EPC advice should not be transferred directly to commercial property. SAP, RdSAP and the domestic Home Energy Model are distinct from the non-domestic National Calculation Methodology (NCM), used through approved SBEM or DSM software. A domestic claim about a heating upgrade’s rating effect is not evidence of the uplift for an office or warehouse.

Dynamic simulation models building behaviour over time, allowing the assessor to examine interactions between geometry, solar gains, thermal fabric, heating, cooling and ventilation. It is particularly relevant where complex features or servicing require the Level 5 assessment route. A heat pump alone does not automatically make a building Level 5.

DesignBuilder’s DSM package uses the EnergyPlus engine and supports Level 5 EPC work. The assessor must use the appropriately approved software version and assessment settings for the jurisdiction and purpose. Read our guide to DesignBuilder and Level 5 EPCs for the wider process.

Detailed modelling can replace unsuitable simplifications with a better-evidenced representation of the building. Where those simplifications understated genuine performance, the rating may improve. It can also reveal that an upgrade delivers less benefit than expected. DSM is not an automatic rating uplift and its standardised EPC calculation is not a forecast of actual annual bills.

Keep the EPC compliance calculation separate from an operational simulation using the occupier’s real schedules, tariffs and loads. The same building geometry can support both studies, but their assumptions and outputs serve different decisions. Not every detailed HVAC feature or control strategy in a general simulation is credited by the approved EPC method.

Start with heat-loss calculations and the temperatures required by the emitters. Lower flow temperatures generally support better efficiency, but existing radiators, coils or air-handling systems must still deliver sufficient heat. High hot-water temperatures, cold-weather operation and defrost can change the overall performance.

Obtain manufacturer performance data at relevant conditions, not just a brochure’s best COP. Check system capacity, part-load behaviour, zoning, controls, distribution losses, auxiliary electricity and any backup plant. DesignBuilder’s heat-pump heating documentation illustrates why performance inputs matter; the EPC assessor must still follow the applicable NCM rules rather than insert an optimistic efficiency.

Survey the electrical supply, plant location, acoustic constraints and maintenance access. These may not all directly change an EPC band, but they determine whether the installation is viable. Refrigerant selection, leak management and commissioning also belong in the design review.

First review the existing certificate and supporting model, checking fabric, glazing, lighting and HVAC evidence. Then compare the verified baseline with a heat-pump-only option, a demand-reduction option, and a combined package. Keep unrelated assumptions consistent so you can identify which changes affect the score.

Fabric and controls improvements can reduce heat demand before plant is sized, avoiding unnecessary capital expenditure and oversized equipment. Where appropriate, test solar PV alongside the EPC improvements. Annual PV yield is not the same as winter heating supply: assess demand timing and on-site use separately.

Ask for the numerical EPC scores as well as the bands, documented assumptions, evidence gaps and sensitivity checks. Compare those findings with a separate operational cost and carbon appraisal. A proposed-model result is an improvement scenario, not a certificate confirming that uninstalled equipment is already present.

Provide floor plans, fabric and glazing specifications, plant schedules, manufacturer data, heating schematics, emitter information, controls descriptions and available commissioning records. For an existing installation, the assessment must reflect what is actually installed and verified. Our DSM modelling checklist is a useful starting point.

An EPC option study is not a complete Part L compliance assessment. Where building regulations apply, project-specific requirements for services, fabric, controls and commissioning still need checking. See our DesignBuilder and Part L guide. Likewise, a proposed EPC result is not confirmation of letting compliance: landlords need to establish the applicable MEES position and final lodged rating.

Before commissioning a heat-pump retrofit, send us the existing EPC and available building information. Our commercial EPC and DSM service can scope an evidence review and improvement study, helping you distinguish a credible rating benefit from an unsupported supplier claim. General guidance only; outcomes require site-specific assessment.