Charting home energy usage

After finishing the epic 1+ year long kitchen remodel, I lost quite a bit of steam to blog and remodel. But the creative juices continue flowing. I am still reading my beloved This Old House magazines and getting new ideas all the time. The bathroom remodel will be next. The planning is really slow going. Meanwhile, I thought I blog about something I’ve been meaning to share for a long time.

Ever since we bought the house, we’ve done quite a bit of home improvement. Back in my college days, I studied HVAC with some classes on power generation. I am really curious as to whether we have improved the energy usage in our home based on the significant improvements we put into it. The only way to tell is to get my hands on energy usage data and a lot of it. It dawned on me that I can grab the electricity usage data from my utility bills. I logged onto my account at the power company website and started copying the monthly meter readings.

Sounds easy right? Well, only if the power company is willing to share all the data online since the start of your account. I can only grab the most recent 40 months of data. Beyond that, the power company “requires a payment of $32.00 per year, or $2.66 per month” (exact words from their email reply to me) if I want to access the rest. We owned the house since fall of 2005. I want data all the way back 5+ years but I don’t want to pay for it. Anyhow, I still have some of the paper statements from the first 15 months we bought the house so I copied data from that. Starting in 2006, my green conscious kicked in and agreed to paperless bill. That’s when the trouble began. The online data only shows dollar amount paid between 2006-2007. Although the cost of electricity fluctuates and the bills include taxes and fees, I figured I can still use the dollar amount data to triangulate something into kWh from the few months before 2006 and after 2007. I am not going to go into all the mathematical details because I am sure all the math whiz out there will have a field day with me if I explain any further. Accuracy is not important here. A ballpark number within +/- 50 kWh would be fine with me.

The other main fossil fuel usage of the house is oil. Yes, we still heat the house with oil and I am not going to convert to gas, ever! A lot of people regret it after converting. Gas people will keep saying we can save money, etc. It might be true for other houses. We spend on average less than $1,000 a year on oil and that includes the annual furnace tuneup in late summer every year.  I am pretty damn sure plenty of people spend way more than that in just the winter months to heat their homes.

The oil usage data is good old fashion pen and paper. Unless I lose the notebook, I don’t need to beg some big company for it. There is still an issue of the oil stick measurement being way off the actual amount. Whenever we get a fill-up, we would measure the oil before and after. The stick reading never matches up the amount on the oil company receipt. I am pretty sure the oil stick is the problem. We had 8 fill-ups by the time I started this project. I used the stick reading and the receipt records to develop an “oil stick multiplier”. Again let’s not dwell into the math. Let’s just accept good enough because what I really want to know is whether we save energy.

I put all the data into a Google Spreadsheet and then generated an annotated timeline chart. Here’s a mini-view of it. The blue line at the bottom is the cumulative oil usage. The red line at the top is electricity. Click here for a fullscreen view of the chart.

The electricity is bouncing all over the place. The cumulative oil usage is steady. I am confident to conclude that the addition of the pellet stove insert is helping us to save oil. But does it mean we are using more electricity? May be. I can’t make any definite conclusion from the red line. I think adding temperature data would help but that’s another quest of data for another blog post a long time from now.

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