Running costs
ZEB running costs: the assumptions that change the answer
Quick answer
A heat-storage system’s annual cost is driven by useful heat demand, efficiency, the electricity price paid across its charging windows and any peak/top-up charging. A reliable comparison makes every one of those assumptions visible.
Start with useful heat, not a generic bill
Separate annual space heating from hot-water demand, then add them to calculate useful heat. A high-heat-loss home and a low-heat-loss home can produce very different outcomes even with the same equipment and tariff.
Why the tariff mix matters
Time-of-use electricity can be relevant to a storage system, but it is not reasonable to price all annual consumption at one cheap overnight rate. A transparent model estimates the off-peak share, the peak or top-up share, standing charges and the actual tariff you could use.
Solar, storage and real-world operation
Solar can reduce imported electricity in some circumstances, but winter heat demand and solar generation do not automatically occur at the same time. Charging behaviour, control settings, storage losses, hot-water demand and weather can all change the result.
Compare a heat pump fairly
An annual heat-pump comparison should use a seasonal performance assumption, not a single laboratory COP. The property’s heat loss, flow temperature, radiator output, controls and installation design can all influence delivered seasonal performance.
What to verify before buying
Confirm tariff terms, smart-meter requirements, charging behaviour, standing charges, heat demand, hot-water needs and the treatment of solar. Retain bills, meter data and itemised quotations: they are better evidence than a universal saving promise.
Use your own property details
The Home Check creates an initial private report before requesting contact details. It does not replace an installer survey.
Check My HomeIndependent guidance; no manufacturer affiliation is claimed.