Wednesday, October 29, 2003

Just a quick post, before I forget (or am too tired tonight)... Jennifer and I decided last night to definitely go with a DC powered fridge. We did some research and found out that liquid propane is not only a non-renewable energy source (duh, we knew that ;-) but also that is is basically just a by-product of crude oil or natural gas processing.

However, going with DC and wanting a decent-sized DC fridge really only leaves Sunfrost who seems to have a monopoly on larger DC fridges.

We haven't made up our minds yet whether to go with a fridge only (9.3 cu.ft. Sunfrost R10) and a chest freezer (5.8 cu.ft. from SunDanzer) or a fridge/freezer combination (10.3 & 3.9 cu.ft. Sunfrost RF16). It's about the same prize, but we'd end up with a cubic foot (or 3 inches in height) less fridge space, but 1.9 cu. ft. (or 50%) more freezer space. Jennifer prefers the combination and I prefer the separation - maybe it's because I grew up with a chest freezer back in Germany. Actually I just checked and our current freezer/fridge combo has a 6.58 cu. ft. freezer and a 14.28 cu.ft. fridge section. So maybe 3.9 cu.ft. is really, really small... The freezer would also be in the non-heated utility room below the kitchen, so that should reduce energy use even further.

What got this all started is that I ordered (from the Kill-A-Watt energy use meter. This site was the cheapest ($34.95) and no shipping cost. I ordered it on Monday and it came with the mail on Saturday. He even sent me this USPS tracking code, but that was no good (other than telling me that it was delivered). It didn't have "where is it now" information.

We used the Kill-A-Watt on Saturday to measure our energy usage of our vacuum (900 Watts). And then on Tuesday morning I plugged it in the fridge outlet. It showed (so I thought) 60 Watts usage. I was kind of surprised that when I opened the door the wattage did not change (so is the lightbulb on all the time???), but hey it was early in the morning...

So in the evening (about 12 hours later) it still read 60 Watts. I read the kWh and it showed 0.73 kWh. That's when I noticed that the 60 was the frequency, not the wattage. Then it started running and used about 212 Watts. Then I opened the door and it used 249 Watts. Ah! A 35 Watts lightbulb ;-)

That's when we compared the usage to the DC fridges. So our fridge, in a house that is at 58 degrees during the day and no door opening, uses .75 kWh per half a day. I haven't checked this morning but I'm sure it used more during those 3-4 "heating hours" where the ambient room temperature was higher. And now is October and the night temperatures dropped to the low 30s (that's right around freezing for our metrics readers out there). So I guess it is about 1.75 kWh/day on a year's average (1.5 kWh in the winter, 2 kWh in the summer). That is roughly 650 kWh a year.

Here is the comparison of freezer/fridge:
RF16 (@70°F): 0.49 kWh/day or 180 kWh/year.
R10 plus SunDanzer (@70°F): 0.19 + 0.28 = 0.47 kWh/day or 170 kWh/year.

So it's about a 1/4 of what we currently use.

[off topic: Did anybody ever wonder why fridge is spelled with a 'd' when refrigerator isn't? Go figure...]

So much for a quick post. Hope you enjoyed reading.


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