Utility Analysis 101: Three Easy Steps to Get Started
A few weeks ago I wrote a blog post intended to help get people started tracking their utility data. To recap the three easy steps were:
Understand Your Utility Bills
Register Online Accounts
Organize The Data
So I assume everyone followed my impecible directions and you now have spreadsheets full of utility data. What to do next? Let's start to analyze those data points and see if we can save some money.
1) Normalize Utility Data
The first step in analyzing utility usage is normalizing the data. Size is the primary way to do this. To normalize by size you just need to find the square footage of your home or building, and then divide your monthly or yearly gas, oil or electric usage by that square footage number. You can do this for each energy type individually, giving you one efficiency number in kWh/ft2/year, and and one Therms/ft2/year (Gallons/ft2/year in the case of oil). I talk about how to use these numbers to compare your property to itself and to other similar buildings in the next two steps.
You can also convert the electric and gas (or oil) usage into a common unit, Btus (British Thermal Units) and combine them to to calculate the Energy Use Intesity (EUI) of your property. EUI is a number that describes how much total energy your proprty consumes per square foot. The EPA use this number to compare buildings for it's recent National Building Competition. More information on EUI here.
To normalize water usage it's better to take the total gallons used at the property and divide by the number of people living in the property (if you're not sure about number of people, bedrooms are a good stand-in). We recommend using people instead of square feet to normalize water use because people are the primary driver of usage. For example, gallons/people/year is a really interesting number to compare before and after your son or daughter goes to college.
2) Compare to yourself
Once you have normalized the data you can start to compare different time periods to determine how much events, like a child leaving the home, affect utility usage. There are two ways to do this comparison: year-over-year and month-over-month. For the first comparison, year-over-year, sum a year of data from before the change and then a year of data after the change and then normalize for any changes in square footage or number of people.
Doing a simple percent change calculation ((most recent year - year before change)/year before change) will tell you if you how much more or less energy you are using for the two years. If you get a negative number, it means you saved energy. Congrats! You can do the same calculation for costs but it's important to remember that changes in cost can be misleading as the price of energy fluctuates. Cost savings may have nothing to do with energy savings.
The second way to compare your energy and water usage is to look at a specific month over two years of data. For example, it's July and you just switched out your incandesant lights for snazzy new LEDs in your living room. The easiest way to see if the change made any difference is to compare July usage this year to July usage last year. The percent change calculation described above will tell you if those LEDs are saving electricity.
3) Compare to others
Using normalized data (EUI or kWh/ft2/year) you can also see how your property compares to other similar buildings. This is often referred to as "benchmarking". Benchmarking your property will tell you exactly how much better or worse you are than similar buildings and in turn show the energy and water savings opportunity. If you are much worse than buildings of similar size and shape, then investing in energy conservation measures is a no-brainer. There are a few options to help you see how your building stacks up.
Our energy tracking platform, www.wegowise.com, is one way to automatically track utility data (lose the spread sheet), compare to yourself and compare to others. We have a link to the free 30 trial below if you're interested in signing up.
There are some others out there as well. The EPA has a free tool called Portfolio Manager that works well for commercial buildings like hospitals and schools. If you like looking at lots of detailed data the Department of Energy's Building Energy Data Book will tell you everything about how buildings, residential and commercial, use energy and water in the United States. Finally the Energy Information Administration also has great charts and graphs to help you understand your property's utility usage.
I hope these two posts helped you understand and analyze your utility usage.