We’ve been in our new home for 24 months now. Around this time last year, we got our twelfth bill from Entergy at the new place. That meant a year’s worth of accumulated energy consumption data. This was a handy baseline, coming just days before we insulated underneath the house with closed-cell spray foam.
So here we are, one year later. As promised, here is the energy use data for the last twelve months.
| Month | kWh Used | Days Billed | Avg. Daily Usage |
|---|---|---|---|
| 11/11 | 571 | 28 | 20.4 |
| 10/11 | 673 | 30 | 22.4 |
| 9/11 | 1169 | 29 | 40.3 |
| 8/11 | 1389 | 31 | 44.8 |
| 7/11 | 1362 | 29 | 47.0 |
| 6/11 | 1229 | 30 | 41.0 |
| 5/11 | 637 | 32 | 19.9 |
| 4/11 | 390 | 28 | 13.9 |
| 3/11 | 642 | 31 | 20.7 |
| 2/11 | 3072 | 28 | 109.7 |
| 1/11 | 3042 | 35 | 86.9 |
| 12/10 | 2368 | 32 | 74.0 |
Obviously the big question is how this compares to last year’s data. Crunch the numbers yourself if you’re so inclined. I’m simply going to put the average daily use side by side.
| Month | Avg. Daily Usage (After) |
Avg. Daily Usage (Before) |
|---|---|---|
| 11 | 20.4 | 23.7 |
| 10 | 22.4 | 30.1 |
| 9 | 40.3 | 57.3 |
| 8 | 44.8 | 68.1 |
| 7 | 47.0 | 46.4 |
| 6 | 41.0 | 46.7 |
| 5 | 19.9 | 18.7 |
| 4 | 13.9 | 23.5 |
| 3 | 20.7 | 88.8 |
| 2 | 109.7 | 92.3 |
| 1 | 86.9 | 174.9 |
| 12 | 74.0 | 82.0 |
On average, we used less energy after the house was insulated. More to the point, if we total up all the kilowatt hours for the respective years, we find we used 23,390 before the insulation and 16,544 after. That’s a drop of almost 7,000 kWh. Even accounting for the freakish cold snap of January 2009, it’s a substantial reduction.
Or so it seems. How much does a kilowatt hour of electricity really cost? It’s complicated. Our bill shows energy charges and fuel charges and lots of stuff I can’t quite figure. I appreciate that Entergy has some tools for analyzing your bill, but I don’t understand why they don’t retain data longer than one year. I do know that our November 2011 bill is $22.97 (31%) lower than our November 2010 bill. I assume our savings more than offset the $2000 we spent on insulation.
Caveats: I talked about energy consumption but this is actually only electrical usage. We have some gas appliances, most notably our upstairs furnace. However, the downstairs furnace and of course the air conditioning system runs on electricity.
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Awesome. There’s still much more that can be done however. Have you thought about the use of “smart” power strips, CFL or LED lighting. I’m still waiting for solar to become viable for my financial situation. If only everyone would audit their energy usage, like you have done.
Right now the projects at hand are sealing my home up, new front door, patio door and garage/entry door.
One kwH is usually in the ballpark of 12-15 cents. So you saved $800-$1000 on electricity. However, what was going on in March of last year vs this year? Looks like a cold one last year and extremely mild this year? With the aforementioned cold snap of January added to March, those two months account for a difference of 4600 kwH, or about 2/3 of your annual savings.
So while I don’t doubt you’ve saved money by doing the insulation, I wouldn’t say with accuracy that all of your savings can be attributed to that alone. You’d need to look at “degree cooling days” or and “degree heating days” that the bills usually have. That way, you establish how much you spent to heat or cool per degree from the outdoor temperature. Otherwise, your comparison is literally baseless. If your bills don’t have these data, you can download a spreadsheet of degree days online for your zip code (e.g., degreedays.net) and then recalculate.
BTW, how much was the closed cell insulation? I was thinking about something like this for our place.
Good stuff! I insulated my walls and roof with spray foam, before I moved in, so I can’t quantify the effect, but my bill seems to be roughly what my old place was, which was 1/3 the size.
Seconded on using the weather info in the comparison.
http://www.nws.noaa.gov/climate/index.php?wfo=lix
Lee: Our neighbor around the way got some grants to install solar panels. I’m not sure we’d ever be able to do that with our metal roof. I’ve installed plenty of CFLs, despite my reservations. I really should look into LEDs, and I didn’t even know smart power strips existed. Thanks.
Garvey: Entergy supplies data for our “degree days” but for some inscrutable reason they don’t track things past twelve or thirteen months, making real comparisons difficult. And even if I go to the trouble, it’s still full of holes. So many variants: vacation days, thermostat settings, air filters. Oh well. Insulating under the house cost just over $2K.
Boxchain: So much data. My head is going to explode.
We’ve had a smart power strip for our TV/VCR/DVD/Wii for a couple of years now. It’s temperamental sometimes, but I like knowing that when we turn off the TV, all those other devices which normally sit idle and leach electricity are completely cut off.
Think about painting your roof white. It’ll reflect a lot more heat in the summer.
j: I’m going to have to call you lowercase j to distinguish you from a certain other J around these parts. Thanks for another vote of confidence on the smart strips.
David: Ha! I don’t think it’s feasible to paint our roof, or most roofs for that matter, but we did have the flat roof of our addition re-surfaced last monith and you’ll be glad to know it’s white.
Editor B,
I randomly came across a picture you posted of a cross with a solar panel attached to it. Curious as to what it is and where it is. Not sure how to directly contact you so I thought this would be the most appropriate item to comment on. Interesting that you keep track of and analyze your utility bills. You are the 1%! If only everyone was that aware. If you get this message, and have the time, could you tell me more about that picture (see link below). You can email me at rschmidt@joule-energy.com. Thanks and keep up the blog! Great stuff.
-Robert
P.S – Metal roofs are some of the easiest to install solar on.
Link:http://www.google.com/url?sa=X&q=http://commons.wikimedia.org/wiki/File:Solar_Cross_New_Orleans.jpg&ct=ga&cad=CAcQARgAIAEoATAAOABAx4Wr-QRIAVgAYgVlbi1VUw&cd=2t8gW1lHb9I&usg=AFQjCNHnz49Xdwu6guyZvO9Fskq6RSqVrg
Link: http://www.google.com/url?sa=X&q=http://commons.wikimedia.org/wiki/File:Solar_Cross_New_Orleans.jpg&ct=ga&cad=CAcQARgAIAEoATAAOABAx4Wr-QRIAVgAYgVlbi1VUw&cd=2t8gW1lHb9I&usg=AFQjCNHnz49Xdwu6guyZvO9Fskq6RSqVrg