Which? published an updated version of its best oil filled radiators review on 29 June 2026, with pricing and availability last checked in June 20261. The consumer organisation said it has tested more than 40 electric heaters over the past three years, including small and large oil filled models from DeLonghi, Dimplex and other brands, and has given one oil filled radiator its Best Buy recommendation1.
Running costs in the review are calculated using the unit price under the current energy price cap, 25.73p per kilowatt hour, and are based on using each heater on its highest setting1. Which? said it takes that setting as the one householders are more likely to use1. The published cost per hour figures range from 8p to 62p across the tested models, though the individual scores, verdicts and per-hour costs sit behind a member login1.
The review lists specifications for each model tested. These include:
| Model | Maximum power output | Size and weight | Thermostat |
|---|---|---|---|
| Daewoo Mini Oil Filled Radiator | 800W | 38 x 29 x 14cm; 3.3kg | Variable, but no specific temperatures in °C |
| DeLonghi Dragon 4 TRDX41025E | 2.5kW | 22.6 x 26.2 x 6.3cm; 18.8kg | Programmable from 5-28°C |
| DeLonghi Radia-S 2kW | 2kW | 65 x 47.2 x 16cm; 11.8kg | Programmable from 10-28°C |
| Dimplex 2.0kW Rapid Eco Oil Free | 2kW | 65 x 57.5 x 17cm; 10.2kg | Variable, but no specific temperatures in °C |
| Dimplex EvoRad EVO2BTA | 2kW | 63 x 47 x 28cm; 11.8kg | Programmable from 5-30°C |
| John Lewis Digital Oil Radiator | 1.5kW | 31.5 x 64 x 28cm; 8kg | Programmable from 5-35°C |
The John Lewis Digital Oil Radiator is listed as available from John Lewis at £65, in store only1. Which? notes that it is not able to show every retailer and that cheaper prices may be available1.
On running costs generally, Which? said its tests have found oil filled heaters heat a test room more slowly than fan and convector heaters but cost less to run, at 33p per hour on average against 60p per hour for fan heaters and 48p per hour for convector heaters1. It also noted that oil filled heaters continue to give out heat after they are switched off1.
Why it matters for households
Oil filled radiators are portable electric heaters, so a household running one is buying all of its heat as electricity at the capped unit rate rather than using gas or another fuel. At 25.73p per kilowatt hour, a 2kW radiator on its highest setting uses about 51p of electricity an hour, and a 2.5kW model about 64p, before any thermostat cycling reduces the time the element is drawing power1. The review's own per-hour figures, from 8p to 62p, reflect how much each tested model draws on maximum and how its controls behave1.
For a home's energy independence, the practical point is that a plug-in heater adds load to the electricity supply a household already pays for, and its running cost moves with the price cap rather than with any contract the household holds for other fuels. Which? frames the trade-off as speed against cost: slower warm-up, lower running cost, and residual heat after switch-off1. Households comparing electric heating options against a fixed installation can see how the numbers stack up in our guides to electric heating running costs and home heating running costs by fuel, and for storage-based electric heating, the Dimplex Quantum storage heater specifications and running costs. Broader context sits in the boilers and heating hub.
What happens next
Which? gives no date for its next update. The review states that pricing and availability were last checked in June 2026 and that the cost per hour figures use the unit price under the current energy price cap1. No further testing dates beyond those already listed have been reported1.
Sources1 cited
- Best oil filled radiators - Which?, which.co.uk