This oil-filled radiator heats more for less

The DeLonghi Radia S Eco Radiator Heater is an oil-filled radiator that produces quiet, efficient heat with plenty of controls to keep things toasty

DeLonghi Radia S Eco Radiator Heater
(Image credit: DeLonghi)
T3 Verdict

A great selection of features make the DeLonghi Radia S a good pick for those who want to warm a room without spending too much.

Reasons to buy
  • +

    Quiet, efficient heating

  • +

    Timer and thermostat provide plenty of control

Reasons to avoid
  • -

    Timer only offers a countdown, not a true timer

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DeLonghi Radia S Eco Radiator Heater - Key specs

Output power: 500/900/1500W
Controls: Three power levels, Frost mode
Other controls: Eco mode, Timer
Dimensions: 14.6 x 6.3 x 25.2 inches

The DeLonghi Radia S Eco (TRRS0715E) is an oil-filled radiant heater. Oil radiators make for some of the best space heaters as they can be more energy-efficient, that's because once they reach temperature they need less energy to keep them hot. However, they are slower to heat a room than fan-based models and don’t offer the direct heat benefit.

This is a more sophisticated and fully featured model than the Amazon Basics model, as t comes complete with a timer, frost mode and thermostat control. It is more expensive, but the extra features are genuinely useful and make the heater more flexible and easier to use. 

This model retails for $129.95 in the US, £119 in the UK and AU$249 in Australia. However, you can normally find some discounts available online. 

DeLonghi Radia S Eco Radiator Heater

(Image credit: DeLonghi)

DeLonghi Radia S Eco Radiator Heater review: design and build

The Radia S Eco looks like a standard oil-filled radiant heater, which is to say that it looks like an old-fashioned steam radiator that has lost its pipe connection. The oil-filled parts are covered in ridges that help the heat radiate, and the controls are located on one side of the body. 

There are six buttons plus a small LED display that shows the power mode and the current target temperature. The top button turns on the device, while the next two set the target temperature. The fourth sets the power level to one of three options, while the fifth turns the eco mode on and off. This uses the three power levels of the heater to regulate the output rather than just turning it on and off in response to the thermostat. The final button enables the timer, which automatically turns the heater on or off after between a half and twenty-four hours time. There is no way to set it to trigger at a certain time, though: it only works as an offset of the current time. 

Below the control panel is a cable holder for the 6-foot power cable. Because this heater can suck down a fairly hefty 1500 Watts, it should only be plugged straight into a power socket, not a power strip. DeLonghi says that is suitable for rooms of up to 250 square feet, but that really depends on the temperature. I found that it was hot enough to warm a larger room, and because the exterior won’t burn you if you touch it, I could put it right next to my desk on a really cold day to warm my feet. 

DeLonghi Radia S Eco Radiator Heater

(Image credit: DeLonghi)

DeLonghi Radia S Eco Radiator Heater review: performance

I found that the DeLonghi Radia S performed excellently, heating my test room quickly once the oil in the system got heated. That took about five minutes, though, so it isn’t great for when you come in from the cold. The fins on the radiator distributed the heat quickly, and perhaps more importantly, kept fingers away from the really hot parts between the radiator blades. The Radia was not as quick to heat as the fan heaters that we tested – it takes longer to warm the things around it, even at the highest of the three power settings. 

I also found that the thermostat worked well. After heating the room to the desired temperature, it silently regulated the output of the heater to keep the temperature steady. Oil-filled radiators may be slower to heat up than fan heaters, but they are also slower to cool down, so they are ideal for keeping the temperature constant. 

Unlike the fan heaters, the Radia was almost silent in use, with only a few slight popping noises as the oil heated up. It was much quieter than the similar Amazon basics oil radiant heater, which made a noise like rain on a windowpane while heating up.  

The anti-frost mode is enabled by turning the heater on and setting the thermostat to 41°F (5°C), which means it will activate when it is just above freezing temperature. That’s useful if you are expecting an overnight freeze, but don’t want to leave the heater running all night. 

DeLonghi Radia S Eco Radiator Heater

(Image credit: DeLonghi)

DeLonghi Radia S Eco Radiator Heater review: verdict

The Radia S shows how adding a few features can make a heater much more useful. The thermostat works well for keeping a room at a comfortable temperature, and the timer means you can set it to turn on just before you get out of bed. It also has what it needs most: plenty of heating power in a compact, silent package that can warm a decent-sized room. 

Richard Baguley

Richard Baguley has been writing about technology since the 1990s, when he left a promising career in high finance to work on Amiga Format magazine for Future. It has been downhill for him ever since, writing for publications such as PC World, Wired and He has tested gadgets as diverse as 3D printers to washing machines. For T3, he covers laptops, smartphones, and many other topics. He lives near Boston in the USA with his wife, one dog, and an indeterminate number of cats.