Space heaters are a reliable way to keep your home warm, but choosing the wrong sized unit can cause quite a bit of discomfort. Choose a unit that is too small, and you risk driving up your energy costs as the heater will strain to generate enough heat to warm a space that is beyond its capacity. On the other hand, if you choose a unit that is too big, you’ll end up paying extra for the heat you don’t use.

All standard space heaters are built under one basic law i.e. 10 electric watts per one square foot of space. For example, a typical medium room in your home would require a space heater that provides 1500 watts. However, to purchase the right size heater for your space, there are a few factors that you need to put into consideration. These are:

  1. INSULATION– Rooms with double the recommended R-Value (heavily insulated rooms) require less energy to heat them, approximately 7.5 watts per square unit. On the other hand, rooms with half the recommended R-Value (lightly insulated rooms) require more power to heat, that is approximately 12 watts per square unit. Space heaters aren’t suitable for use in rooms without insulation such as garages and basements. Heat transfers at a very high degree thus it gets drained faster than it is generated. Consider improving the R-Value in these rooms if you spend more time there than in other rooms.
  2. HIGH CEILINGS– Most space heaters work with the convection principle. When turned on, the air near it is heated. It then expands upwards displacing the cooler, denser air which sinks, gets in contact with the heater, heats up, expands upwards, and the cycle continues. This type of heating works best in rooms with low ceilings. For rooms with high ceilings, the hot air gathers at the ceiling and takes time to come back down and warm the occupants. To make up for this, increase the wattage of your heater by 25 percent for every two extra feet space above. For example, a 10 by 12 room with a 10-foot-high ceiling would require a heater with 1500 watts to heat it while the same sized room with a 12-foot-high ceiling would require a space heater with at least 1800 watts to heat it.
  3. WINDOWS– Windows (even the best ones), are very poor insulators. They make up a good percentage of a classic home, but they are responsible for a majority of the heat loss in a house. Install windows with materials that are good at trapping heat to counter the “window effect” or increase the wattage of your space heater.
  4. OUTSIDETEMPERATURE – the amount of heat loss from your home depends on its construction as much as its environment. If your home is located in an extremely cold region, you will lose heat at a much higher rate compared to those in warm regions. You can make up for this by increasing your heater wattage estimation from 10 watts per square foot to 15 watts per square foot when shopping for a space heater.

There you have it. A few measurements and a bit of math will help you keep your home warm all winter.