How to compare the specs of heat pumps, EV chargers and home batteries

Putting two datasheets side by side sounds simple: higher efficiency wins, lower noise wins. In practice, manufacturers do not always measure the same thing, at the same temperature or in the same unit. This guide shows what to look for so that you compare like with like. It is the same approach we use for the comparison tables on VersusIndex.

Start with an official source

Not every figure is equally solid. We rank sources in this order, strongest first:

Every product page on VersusIndex shows the source and date for each value. If two models draw on different sources, take extra care: a value from a register and a value from a brochure were not necessarily produced in the same way.

Compare under the same test conditions

The classic pitfall is a heat pump’s seasonal efficiency (SCOP). The energy label gives the efficiency for two applications: low temperature (35 °C, typical of underfloor heating) and medium temperature (55 °C, typical of radiators) ⁴. Testing follows EN 14825, the same standard that Heat Pump KEYMARK certificates are based on ².

The gap is large. Across the 1,000 heat pumps in our database, whose figures come from the German BAFA list ⁵, the median SCOP is 4.86 at 35 °C and 3.68 at 55 °C. Model by model, the 55 °C SCOP is about 24% lower (median). A brochure that quotes only the 35 °C figure when your home has radiators paints too rosy a picture – and many UK homes do have radiators.

So always check:

• temperature: 35 °C or 55 °C, and for air source heat pumps the outdoor temperature too;
• climate zone: the label distinguishes average, colder and warmer climates ⁴, so make sure every model is quoted for the same one;
• size: compare within the same output band, because a larger unit behaves differently for the same heat demand.

Noise: sound power is not sound pressure

Two quantities are often confused. The energy label states the sound power level (LWA) in dB, indoors and outdoors ⁴. That describes the unit itself, wherever it is installed. Sound pressure is what you hear at a given distance; it is always lower than the sound power and depends on the distance and on nearby walls.

A brochure quoting “35 dB(A) at 3 m” and a label showing 53 dB(A) sound power can describe the same unit. For reference, the median outdoor sound power in our database is 53 dB(A). Always compare sound power with sound power. On our heat pump pages we convert the sound power into an indicative minimum distance to your neighbour – a first check, not a substitute for the installer’s MCS 020 assessment.

Nominal versus usable

For home batteries, the pitfall is capacity. Nominal capacity is what the cells can hold; usable capacity is what you can actually draw, because the battery protects itself against deep discharge. Manufacturers are not consistent: of the 39 home batteries in our database, the manufacturer states only the usable capacity for 27 and only the nominal capacity for 8. For the 4 models where both are known, usable capacity is 95% to 97% of nominal. Compare usable with usable.

EV chargers have a similar trap with power. A charger only delivers 11 kW on a three-phase supply and when the car can accept it. Look at the number of phases and the maximum current per phase, not just the figure in the product name.

What else counts in the UK

For the Boiler Upgrade Scheme, the installer must be MCS certified, and MCS certification checks both that the installer is competent and that the products they use meet the correct standards ³. Grant amounts and conditions are covered in our heat pump grants guide.

Checklist

1. Check which source is behind each figure and prefer registers.
2. Compare SCOP at the temperature that suits your heating system.
3. Compare sound power with sound power, not with a pressure at a distance.
4. Check whether a capacity or power figure is nominal or usable.
5. Compare within the same size band.

With these five steps you can put the heat pumps, EV chargers and home batteries in our database side by side fairly.