What's Your Home Energy Efficiency Number?
I've analyzed and improved the energy efficiency of numerous homes. The starting point is, of course, the analysis because you want to put your efforts—and your dollars—where they're going to generate the best results.
It drives me crazy, for example, when I see stories in the media about home energy efficiency because their top two recommendations are almost always to weatherstrip your doors and caulk your windows. Arrrrggghhhh! There are much bigger holes in your building enclosure than those.
Here's a simple thing you can do to find out where your home stands on the energy efficiency scale, from super efficient to energy hog. All you need is 12 months of your energy bills (electricity and gas). With your energy bills in front of you, find out how many total kilowatt-hours of energy you used for those 12 months. Divide by the square footage of conditioned floor area. (To do this properly, you have to convert all energy units to kilowatt-hours. See below for an easy way to do that.)
The number you get will almost certainly be between 1 and 30 kilowatt-hours per square foot per year. Here's the breakdown of how to interpret your number:
- 0 - 5: Super efficient
- 5 - 10: Efficient
- 10 - 15: Moderate
- 15 - 20: Bad
- > 20: Energy Hog
So, what's your number?
If you need some help with the calculation, I've put together a home energy calculator in the form of an Excel spreadsheet that makes it easy. All you do is plug in your numbers, and it spits out your home energy efficiency result. It also gives you a graph of your monthly energy use over the 12 month period, as shown below.
If you'd like to go further with analysis or improvements, call a home energy rater for assistance.