How many watts per square foot for your electric heater?
Sizing your electric heater is necessary for an optimized heating solution that is just right. If it is too big, then you may end up paying extra for capacity that you will never need. If you wind up with an electric heater that is too small, then it may fail to keep you cozy and comfy. Heaters that are too small could keep working continuously since the thermostat may never reach the target temperature.
Factors that Affect Wattage
On average, 10 watts per square foot will work well on most spaces where the ceiling is no more than 8 feet high. However, you may need extra heating capacity if you live in a particularly cold place. Likewise, you may have to invest in extra heating capacity if your property has a lot of windows or if the ceiling is quite high.
Having a ceiling fan may be a helpful solution since it can allow the quick distribution of heat.
If you have to replace your old heater, then it is advisable to buy a heater of the same wattage if the old heater worked well for you.
How well your heater performs in a given space depends on your room attributes. If your room is north-facing, has poor insulation and has lots of draughty windows then the heater may not be optimal for the given space.
The shape of your room could also be one factor. If your room has a different shape then this could have an effect on air circulation and leave some parts of the room colder than other sections. This can happen for instance, with plenty of bookshelves.
Wattage for High Ceilings
Bear in mind that the 10 watt normally works for ceiling heights of around 8 feet.
Thus, if your room measures 20 by 20 feet while the ceiling height is 8 feet, then the wattage requirement may be = 20 x 20 x 10 = 4000 watts.
But what if your ceiling height is in excess of 8 feet? In that case, it is better not to use the 20 watt rule since it is generally applicable to 8 feet high ceilings.
For higher ceilings, it is better to go with volume or cubic feet. Thus, for each cubic foot of room space, you should allow $1.25 watts.
Thus, for a 9 foot high room measuring 20 by 20 feet, the required wattage is = 20 x 20 x 9 x 1.25 = 4500 watts.
Conclusion
You have to contemplate certain factors to decide how much wattage will be sufficient for your electric heater. While 10 watts per square feet is a rough general guideline, you may have to factor in other issues like ceiling height, number of windows, how cold your area is and other issues.
Additional Reading
