EPC data
Electric storage heaters: why they drag down EPC ratings and cost more to run
5 min read · Updated May 2026
Storage heaters appear frequently on EPCs for flats, conversions, and 1960s–1980s properties without gas connections. If you're buying one of these and the EPC lists “electric storage heaters” as the main heating type, it's worth understanding exactly what that means — for your bills, your EPC rating, and your options.
The short version: storage heaters are significantly more expensive to run than gas, give you less control over when you're warm, and are one of the main reasons otherwise decent properties end up with D or E ratings.
How storage heaters work
Storage heaters charge overnight using off-peak electricity (typically midnight to 7am on an Economy 7 tariff, which prices night units at about half the day rate). They store heat in ceramic bricks inside the unit, then release it gradually through the day via a damper or fan.
The fundamental problem is timing mismatch: you heat up during the night when you don't need warmth, and try to release it during the day when you do. By early evening — when many people want their home warmest — the stored heat is often largely depleted. You then either endure a cold evening or pay full day-rate electricity for a top-up panel heater.
Newer “smart” storage heaters have better controls and can be programmed more precisely, but the fundamental economics remain: you're heating with electricity at a premium over gas, even on the cheaper night rate.
The cost comparison
| Heating type | Unit cost (2026) | Annual cost, 2-bed flat* |
|---|---|---|
| Mains gas (combi boiler) | ~6p/kWh | ~£700–£1,000 |
| Economy 7 storage heaters | ~13p/kWh (night rate) | ~£1,400–£2,000 |
| Standard electric (panel heaters) | ~25p/kWh | ~£2,500–£3,500 |
* Estimates for a typical 2-bedroom flat, moderate usage. Economy 7 day rate (~25p/kWh) applies to daytime top-ups.
On a pure economy 7 night rate, storage heaters cost roughly twice as much as gas for equivalent heat output. Factor in some daytime top-up usage and the gap widens further.
The EPC rating impact
The SAP methodology used to calculate EPC ratings factors in the cost of the fuel used. Because electricity is significantly more expensive than gas per kWh, storage heaters push EPC ratings down even in well-insulated properties.
A 2-bedroom flat that would rate C with gas central heating might rate D or even E with storage heaters — same insulation, same building fabric, just a different heat source. This is one of the reasons many older leasehold flats (which often can't install gas due to lease restrictions or building configuration) struggle to reach C on the EPC.
What you can do about it
Option 1: Upgrade to smart storage heaters
Modern storage heaters (Dimplex, Glen Dimplex Quantum, Elnur) have significantly better controls — app-connected, adaptive charging based on weather forecasts, better insulation to retain heat longer. They cost £300–£700 per unit and can be fitted without any building works. They don't eliminate the underlying cost premium of electricity, but they reduce waste and improve comfort.
Option 2: Install a heat pump
For houses and some flats with outdoor space, an air source heat pump replaces storage heaters entirely and qualifies for the £7,500 Boiler Upgrade Scheme grant. Running costs are comparable to gas, and the EPC rating improves significantly. Requires installing wet radiators or underfloor heating throughout — a major project in a flat.
Option 3: Install gas (if possible)
If mains gas is available, connecting and installing a combi boiler is usually the most cost-effective long-term solution. In a flat, this requires the freeholder's consent and potentially a flue through the building fabric — not always straightforward but often achievable.
Option 4: Add solar panels
If the property has a suitable roof (more relevant for houses), solar panels can reduce electricity costs significantly — particularly if consumption can be shifted to daylight hours. Less applicable to flats where roof access and ownership are complicated.
The leasehold complication
Many storage-heated properties are leasehold flats. Changing the heating system in a leasehold flat typically requires the freeholder's written consent under the terms of the lease. Installing gas (requiring a flue), a heat pump (requiring outdoor unit), or significant internal works may all require consent that isn't guaranteed.
Before buying a storage-heated leasehold flat with the intention of upgrading the heating, check the lease and seek written confirmation from the freeholder that the upgrade you have in mind would be permitted. Don't assume.
Does it affect the offer price?
Yes — and it's quantifiable. If a storage-heated flat costs £1,000–£1,300 more per year to heat than an equivalent gas-heated flat, that's a real ongoing cost difference. Over 5 years, that's £5,000–£6,500 in additional bills, before accounting for any upgrade costs.
This is a legitimate consideration in the offer price — particularly if upgrading the heating system requires freeholder consent that is uncertain or expensive to obtain.
The short version
- Storage heaters cost roughly twice as much as gas per unit of heat — a real and significant ongoing cost
- They drag EPC ratings down, often pushing properties to D or E even with reasonable insulation
- Smart storage heaters improve control and reduce waste but don't fix the underlying cost premium
- Upgrading to a heat pump or gas requires checking the lease first in leasehold properties
- The bill difference over 5 years is a legitimate basis for negotiating the purchase price
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