Short Term Energy Monitoring to Define Energy Efficient Homes
One of the first things I do, after introducing myself at a home energy audit, is ask if I can see current electric and gas bills. I feel like I'm being rude, that I'm asking for personal information. A number of clients, by the way they respond, think I'm being rude too. When your looking for energy efficient homes, sometimes a little rude is OK.
It's an uncomfortable moment, like asking a women their dress size. I think 99% of the time, a women is going to be embarrassed by providing their dress size, as they believe whatever size they wear is too big. They might look like a fence post, but they would feel their dress size is too big.
Same is true of an electric bill.
Somehow the word got out that people should be ashamed if their electric bill is too fat. Shame on you if your home is not one of the energy efficient homes. A fat electric bill brings out an interesting response from homeowners, they are likely to explain by saying something that sounds like their trying to loose weight. "I'm sorry, we've been trying to cut down."
I'm not trying to investigate the reason why Lake Mead is turning into a puddle or why Washington DC may have to shave in the dark, I'm only trying to get a look at one of the few documents that can give some insight into home energy saving potential.
Duct Blaster Test
We have a hundred ways to determine if the body is fat - if one body is fatter than another - or if a body is likely to get fat in the near future. Everything from a talking weight scale on the bathroom floor to the number of calories in a peanut bar cookie can point the way to success. Just look at the number of pills down at the drug store that promise to take off a few pounds and keep them off.
At anytime, a person can climb up on the old scales and see exactly how their doing. Kick off the shoes and ditch the winter coat as you step upon the scales, you're about get a pretty good idea how your special order, energy efficient, weight loss breakfast bars are helping out.
When it comes to energy efficient homes and trying to determine how energy efficient measures, upgrades, retrofits, and behavior changes are effecting energy gain and loss, the electric and gas bill is about all we have to weight long term success.
Utility bills have their limitations as analytical tools for both homeowners and energy auditors, because they are sensitive to changes in occupant behavior and to climate conditions that can cloud the effect of an energy retrofit. After a retrofit has been completed, it takes months for energy bills to accumulate, and so it maybe a year before the household knows if the retrofit had any true energy saving benefit.
Short Term Energy Monitoring
Short term energy monitoring can give both the homeowner and the auditor much quicker information to evaluate the promising energy efficient homes. Most fuel driven appliances, meaning electric, natural gas, propane, oil and diesel, use energy at a constant measurable rate. We can use this measurable rate to calculate short term energy retrofit benefits.
If you know how long a device operates and you know it's power rating, you can calculate it's energy consumption over time.
1. A 100 watt light bulb 2. Burning for 10 hours 3. Uses 1,000 watt-hours 4. Or one kilowatt hour of electricity.
1. A 100,000 Btu per hour Furnace 2. Operating for 10 hours 3. Uses one million Btu's
Two activities are necessary to successful short term energy monitoring.
1. Measuring Power
2. Measuring Operating time.
You can buy a recording watt meter, which will measure both time and power, and connect to electric circuits around the home. The kill-a-watt meter will measure energy use over time for appliances like refrigerators and window mount air conditioners. Heavier meters will measure clothes dryers and water heaters.
Measuring the power of a gas furnace involves a stop watch and the ability to count the revolutions of the dials on the gas meter. By counting the dial revolutions you can learn the number of cubic feet per minute the furnace or other gas appliance uses. Then take the number of cubic feet and multiply the cubic feet by the number of Btu's in a cubic foot. Gas differs slightly, so you will need to ask your gas company for Btu's in a cubic foot.
By using both long term energy efficiency indicators like a power bill and using short term energy use indicators like kilowatt meters and short term energy monitoring calculations, you and the auditor can get a pretty good idea if your home is one of the energy efficient homes or if your home needs to loose a few therms.
If your lucky enough to have a certified Home Energy Auditor come to your home, don't be ashamed if your power bill looks like it could use a few diet pills. Have the bill ready and present it to the auditor so you both can learn a few things about your homes long term energy use.
Thank you for stopping by, hope to see you again real soon, but I won't leave the light on for you...