Convection space heaters without fans rely on the natural air circulation in a room to distribute heat, rather than using a fan to direct the flow of hot air. As a result, these heaters are generally quiet but slower at heating a room than models with fans.
Convection heaters are available in a wide array of styles and designs. EnergySavers.gov, a U.S. Department of Energy website, recommends models containing "a heat transfer liquid, such as oil, that is heated by the electric element." According to the site, the heat stored in the fluid allows the heater to provide more constant, even heat without cycling on and off. The most familiar heater of this type is the classic oil-filled radiator. Experts recommend heaters of this type for well-insulated rooms where the heater will be on for long periods of time. Tests at Which? magazine, the British equivalent of ConsumerReports.org, indicate that oil-filled radiators are quiet and economical to use but generally less effective than other types.
Oil-filled space heaters are heavy but stable, and many models have casters and handles that make them easy to roll around on a level surface. The oil-filled fins are permanently sealed and never need refilling. The main drawback is the time required to start producing significant warmth; they're not useful in situations where you need quick heat. Also, most models don't include thermostats. The surface of an oil-filled radiator can get hot to the touch, although some models include a cool-touch exterior casing.
DeLonghi oil-filled radiators are recommended more often than any other brand. The DeLonghi Oil-Filled Radiator TRD0715T (*Est. $75) , which earns the best reviews overall, has "thermal tunnels" designed to direct most of the heat out the top of the unit, rather than the sides. Some owners like this feature because the sides stay cool, but others dislike it because there is no heat near floor level. This space heater performs reasonably well in comparison tests, with good-to-excellent ratings for heating performance and ease of use and excellent ratings for quiet operation.
Users at Amazon.com are also impressed, giving the DeLonghi TRD0715T Oil-Filled Radiator with Timer a 4-star rating after nearly 400 reviews. Its programmable timer, which can be set in 15-minute increments over a 24-hour period, earns praise from users, along with its heat output, quiet operation and safety. "This new heater is much safer and heats better than all the other fan-type space heaters I have had in the past," says one owner.
However, we did find some complaints. Quite a few users say the DeLonghi TRD0715T heater takes too long to heat up, which is a common complaint for oil-filled radiators. The most persistent and troubling complaint, however, is that this space heater gives off an unpleasant chemical odor when it is first used. Although most radiator-style heaters will produce such a smell for the first few hours of use, many consumers on Amazon.com and Epinions.com say their DeLonghi space heaters continued to smell bad for days or even weeks.
DeLonghi also gets high marks for the ComforTemp EW7707CM Oil-Filled Radiator . More than 250 owners have weighed in at Amazon.com, and the space heater enjoys a solid 4-star rating. Users say it produces quiet, even heat and has simple, easy-to-use controls. "This heater is inexpensive, durable, and does an excellent job of heating our home in Connecticut during the dead of winter," says one owner. The DeLonghi ComforTemp EW7707CM Oil-Filled Radiator is very effective for heating small-to-medium-sized rooms, and -- unlike fan heaters -- it doesn't make any noise while operating.
However, like the DeLonghi TRD0715T, this space heater receives several complaints about a persistent odor, and some say their unit leaked oil -- a potential fire hazard. Several users whose space heaters broke within the warranty period say they were frustrated to find they would have to pay for the cost of shipping the 25-pound machine back to the manufacturer or to the nearest service center. Dan Crane of Slate.com is also unimpressed with the DeLonghi ComforTemp EW7707CM Oil-Filled Radiator space heater; he says it takes a good 20 minutes to heat up and lacks safety and convenience features.
Another type of convection heater, the micathermic flat-panel heater, uses flat sheets of the mineral mica as its warming element. These models can either stand upright or be mounted on a wall. These space heaters are not as popular as oil-filled radiators or ceramic fan heaters, but the Soleus Air HM2-15R-32 Micathermic Flat Panel Heater gets high marks in one independent test. It scores excellent ratings for temperature control and noise, while it receives very good marks for safety and ease of use. The Soleus Air Micathermic Flat Panel Heater has an adjustable digital thermostat, two heat settings and a 12-hour auto-off timer.
User reviews for the Soleus Air HM2-15R-32 are mixed. In nearly 50 reviews at Amazon.com, most owners say they're pleased with the heat output and silent operation. "Most important, the heater is absolutely silent with no annoying fan noise," says one owner. Users also like the remote control, which they say is convenient for changing the temperature or turning the heater on or off without getting out of bed on a cold night. However, reviewers report a number of durability problems, and we saw a few complaints that the Soleus Air heater has an off-putting smell.
Experts also had good things to say about the DeLonghi Mica Panel Radiator HHP 1500, a model that has since been discontinued. It's been replaced by the DeLonghi HMP 1500 Mica Panel Heater , which can be mounted to a wall or placed on wheels. The heater comes with an adjustable thermostat and two heat settings -- 1,500 watts or 750 watts. It also includes a number of safety features, such as a tip-over switch and a thermal cut-off.
Users at Amazon.com were mostly impressed with the DeLonghi HHP 1500 Mica Panel Heater, praising its heat output, quiet operation and compact design. However, like most mica space heaters, owners say it was slow to heat up, and some wished it had a timer. The new model, the DeLonghi HMP 1500 Mica Panel Heater, has yet to attract any user reviews. Except for some slight design differences, the two models are nearly identical.