I live in Colorado, and when it's cold it is very, very cold. Since I hate paying high heating bills, I typically have my thermostat set to a chilly 62°F. My husband and I have gotten used to this, and really like being able to use a warm comforter while the air stays cooler.

There are some nights, however, that even this setting seems too high and the heater is running a lot more than I'd like it to. When it's below 0° overnight, or even sometimes during the day, we occasionally break out our oil-filled space heater when we're only using one room. That has me wondering: is it more energy- and cost-efficient to use a space heater for 8–10 hours while keeping the thermostat low, or does the wattage required by a space heater make up for the cost of running the heating system?

The answer is: it depends. There are multiple factors to consider such as:

  • How much energy the space heater uses (in my case, 1500 watts)
  • How efficient the heating system is (mine is old and not so efficient)
  • How much the utility charges, for example, for natural gas and electricity (my utility company charges different rates for both).

Beyond that, the variables get even murkier: how cold it is in the home (obviously, if it's below 50°F it will take some time to build the heat back up later on, plus there's the matter of frozen pipes to think about)? How hard does my space heater need to work to keep the room warm? How well can I control my space heater's heat setting?

Let's start with a basic tenet: electric space heaters are less efficient than HVAC systems. I cannot replace my heating system with room heaters if I want to save money. Besides, who wants to wander around their house manually managing space heaters? It's too time-consuming (and potentially dangerous too, since they can pose a burn hazard).

If you're considering buying a space heater, take a good look at the features and warranty to make sure you're getting the most energy-efficient model for your needs. Here are a few tips:

  • Buy one that is made to heat a room about the size that you plan to use it in
  • Compare wattages of similar models to see which uses less energy
  • Look for thermostat and timer settings—these can save energy and keep the room from being overheated

Look for more tips for using space heaters safely and efficiently on our Portable Heaters page. In addition, see our seasonal tips for more ideas for staying warm in the winter.

In the meantime, I'm using my space heater on the lowest setting on only the coldest nights, and keeping that cozy comforter on!

Andrea Spikes is a communicator at DOE's National Renewable Energy Laboratory, which assists EERE in providing technical content for many of its Web sites.