Eternal Vigilance is the Price of Efficiency — power is ever stealing [into your home]. — Me, with apologies to Wendell Phillips, Thomas Jefferson, or whoever said it first.
Those who know me know that I’m a little obsessed with energy, specifically renewables, and conservation/efficiency (it all goes hand in hand; with more conservation & efficiency, renewables can be that much closer to powering our world).
To that end, I’ve done a lot of efficiency work on our house, and have tried to make some behavioral changes as well, to conserve. Some of this work has been chronicled in an answer at Quora.
But how do I know if it’s really paying off? Not from a financial payback sense, but from a “am I actually using less energy than before” sense? We measure, of course… and we graph.
Let’s start with Electricity. It’s easy to measure from monthly bills, and since by and large we don’t use AC, our electricity use isn’t terribly seasonal (modulo more lighting in the winter, and a couple hot weeks in the summer). I’ve found two types of graphs to be informative. The first and most obvious is to graph usage over time. Because the number of days in a given utility bill can vary, I plot the usage from each month’s bill, normalized to kWh per day for that period:
The pure month-to-month is pretty noisy; a rolling 6 month average gets things reasonably smoothed out, and there I can see a trend that I like. It’s plateaued a bit, though; we seem to have reached an ongoing average of around 12 kWh/day, or around 365kWh/month. While that is less than half of the Minnesota state average, I do know of a family of four who can come in under 200kWh/month – so there is room for improvement (somewhere… finally getting this server down to 18W will help to the tune of about 10kWh/month).
(Note, above is actual household usage, independent of any solar production, which is another variable. I have, however, plotted the ongoing percentage of our use covered by solar on the green line.)
But there is indeed some seasonal variability; for that, it’s neat to plot each month against the same month from previous years, a trick I learned from the soon-to-be-defunct Microsoft Hohm:
Apparently, around September 2009 is when I started paying attention. A few months after that, it got even better. Early on, it was obvious things like getting rid of the insane power-hogging Pentium 4 Mythbox that ran 24/7, and not leaving the electric heater running in the basement. Many other improvements followed – incremental lighting efficiency improvements, diligent use of the clothesline, making sure all computers slept/suspended appropriately, etc. What amazes me is that we’ve cut it almost in half since those early days. Maybe I was just an unabashed power-pig before?
It looks like we’re hanging in there at 12kWh/day – I’m sticking to my diet. Yay! I’ll talk about graphs for water and gas in subsequent posts. I’ve slipped a bit on one of them. Stay tuned…