You've seen the ads - "Amish made space heaters cut your utility bills by 50%" or similar claims. There are also a series of ads for heaters that look like a big wood box, claiming their safety and energy efficiency. Every month, I get questions about these devices from people looking to save money on their utility bills. What's the real answer?
The first, and most important thing to know is that ALL electric space heaters, from the $29.99 device from your hardware store to the $399.95 miracle heater are essentially 100% efficient at converting electricity into heat. They work on the same principle as a toaster - electricity passes through a heating element and heats up then a fan blows the air around the room.
The way these devices differ is their air distribution. some don't use fans, relying on convection. For example, if you have electric baseboard heating in your home, these work this way. Others are small metal cabinets that have glowing metal elements and a noisy fan to blow air around the room. Others are shaped like radiators and are filled with oil.
All of these devices work at getting heat into the room. In fact, I've used the oil-filled radiators and like them quite a bit for heating rooms in emergencies. These particular devices have no exposed super-hot element. Instead they have the radiator fins, which get hot, but not enough to start a fire. The heat is dispersed naturally through convection, so they operate silently, other than a periodic gurgle.
What you need to know however, is that all of these electric space heaters produce the same amount of heat for a given amount of electricity. This $50 electric radiator is just as efficient as a $350 electric miracle heater. But here's the kicker - in most areas of the country, pure electric heat costs two to five times as much as most other conventional sources of heat, such as natural gas and heating oil.
This is a critical factor. If you're looking to save money by running a few of these devices around your home instead of running the furnace, you're in for an ugly surprise as your electric bills shoot through the roof! The only way you might save energy is if you turned off your central heating system and closed all the doors to the rooms in your house. Then, you put one of these heaters in one room with you. You would be warm in that one room and freezing in the rest of the house. That might save some on your heating bill.
Note that these devices are not to be confused with heat pumps. Heat pumps actually work to give you several times the amount of heat out for a given amount of electricity in. So, the Fujitsu 12RLS that I reviewed elsewhere, actually is very efficient and cost effective to run. However, even that, at current energy prices (Fall 2009) does not have as low an operating cost as natural gas.
Just remember, when you see ads claiming some sort of "energy efficiency breakthrough", in all likelihood, they're taking advantage of people's fear of high energy costs. Basic physics dictates how efficiently heaters operate, and no new physics has been discovered.