This week’s article comes from one of our senior energy auditors, John Matejka (read his bio here). He’s been in the industry for years so he really knows his stuff. He picked a great topic that has great information for EVERYONE (I even learned some things)….analyzing your utility bill. If you’re like me, you just pay your utility bill each month without even looking at it. But it is good to dive into your bill and really break things out. Hope you enjoy this read.
In comes John…
Do you know how much energy your home uses on a daily basis? You may look at your utility bill when it shows up every month, but do you consider what used all of that energy? The amount used by your heating and cooling equipment changes based on the conditions outside, but the rest of the appliances in the house operate on a steady basis(with exceptions such as vacations and long-term houseguests). These two portions are called seasonal consumption and baseline consumption. The baseline includes things like water heating, refrigeration, lighting, entertainment, etc. You can estimate your baseline consumption by looking at a full year’s worth of bills. Find the three months with the lowest consumption(summer for gas bills, spring and autumn for electric), and average them out; that is your baseline. You can then subtract that amount from the other months to see your seasonal consumption. Let’s look at two examples of electric bills.
This is a 1700 square foot home, inhabited by a retired woman. Her stove and water heater are both gas-powered. She has mostly incandescent light bulbs. Her attic insulation is rated at R-17, and her duct system is leaking 50%. The usage in her three lowest months averages out to 558kWh, or roughly 18.6 kWh per day. Subtract that from 1601 in July and we see that she used 1043kWh to cool her home that month, or almost an additional 36kWh per day.
This is a 1500 square foot home, inhabited by a young woman and her husband. She works from home every day, and conserves energy by keeping the air conditioning set in the high 70s. The water heater is electric and all of the light bulbs are CFL or LED. Her attic insulation is rated at R-4, and her duct system is leaking about 15%. The three lowest month average out to 329kWh per month, or roughly 10kWh per day. Subtracted from the July bill, we see she used 531kWh to cool her home, or 16.6kWh per day.
So what does all of this tell us? Both women are at home during the day and using electronics(television for one, computer for the other). The homes are similarly sized. One thing we can take away from this comparison is how easily baseline consumption adds up, and also how easily it can be reduced. CFLs and LEDs normally use 75-80% less energy than incandescent bulbs of similar brightness; a light turned off in an unused room uses 100% less energy than one left on. Conservation is equal parts performance and behavior. Both homes have performance issues in their insulation and duct systems, but one woman was more willing than the other to sacrifice a few degrees of comfort in the interest of conservation.
The main point here is that you can learn a lot about your energy usage from your utility bills. Analyzing them and learning what is going on in your house on a daily basis is a good first step towards saving energy and money.