for the good time Jerry’s ramblings…

Now that we’ve been in our house for a few years, I’ve seen enough electric bills to know that we really do consume a lot more energy here. This was particularly highlighted when I looked into adding solar panels to the house. What has perplexed me is why, exactly, this is happening. I’ve been working at auditing devices for a while to try to unravel the mystery. In the summer months when we aren’t spending as much energy on heating, I’m especially wondering where all of that energy is going?

I hate to admit it, but last month, with basically no A/C, we consumed 600KWh. Of that, I suspect 250KWh is explained by the water heater. So where is the rest going? I think I found the next large chunk in an obvious place – the refrigerator.

We have two refrigerators in our house, one of which was probably made in the 1980′s, ironically named the “Amana 22 energy saver”, a white elephant left in the house when we moved in. Three years ago I incorrectly assessed its energy consumption and thought nothing of running it since the annual cost seemed fairly small. But since my estimates on home energy consumption weren’t adding up to the total bill, I decided to take the measurements again, this time running the study for 200+ hours. The results surprised me.

Last month, our refrigerators consumed 33% of our total bill (200KWh). Ouch!

A quick search at Home Depot shows a basic, no frills refrigerator / freezer for $800 that consumes ~37KWh/month. Compared with the white elephant, it will pay for itself in a mere 4.5 years at our “green” electricity rate of $0.12/KWh (and rising…).

Now, ignoring space constraints, does it make sense to buy one big refrigerator or two medium sized refrigerators? I took the energystar.gov refrigerator summary and plotted annual energy vs. volume. As far as I can tell, once you get to ~15cf and larger, energy consumption versus volume scales proportionally*. It doesn’t appear that there is a huge benefit of one versus two refrigerators if you need a more than 30cf of space. One interesting note, though – if all you really want is extra freezer space, a chest freezer may be a better option than another refrigerator. Too bad I didn’t realize this 3 years ago.

* I should note that these results aren’t entirely surprising. As far as I can tell, Energy Star criteria are at least partially defined by KWh/cf.