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Then I thought about it. I realized this was an opportunity rather than an inconvenience. I can save energy costs! I was inspired some time ago by the Fort Collins net-zero electric energy home, and maybe this is one of many steps I could take to reduce my energy consumption at home.
I did the calculations (see comments for my actual calculations) and found that I will be saving $68.58 per year on energy costs by having a manual garage door opener in place of an electric one.
I was speaking with a coworker about this very calculation, and she pointed out that the marginal utility of having an electric garage door opener versus a manually-opened garage door is highly in favor of the electric opener, given the cost savings. For some people, spending $5.71 per month to have an electric garage door opener is worth the cost. For myself, it's not; we only park the bikes in there, not the car, and don't use the remotes -- just open it from the inside anyway.
For now, I'm happy with the arrangement. The cost savings is definitely worth the marginal utility loss.
How I arrived at garage door opener energy cost:
ReplyDeleteFirst, I used the table from http://www.absak.com/library/power-consumption-table# to find the energy output of garage door opener (350 W) and associated two lights (120 W).
Second, I used the load calculator form from http://www.absak.com/pdf/docs/loadeval.pdf to calculate the load. A typical garage door opener run at .133 hours/day (8 minutes, 2 minutes per use at 4 uses per day) plus the two lights on mine (which stay on for about 5 minutes after door is used) at .333 hours/day each. There's also the Load Correction Factor: "Load Correct Factor compensates for losses in the system. Batteries and other power system components are not 100% efficient. We have found that increasing load value by 30% adequately factors in these losses." So the corrected Watt-hours/day is 124. This translates to 45.26 kWh/year.
Next is standby power, also known as phantom loads. According to http://standby.lbl.gov/summary-table.html, a garage door opener's average standby power is 4.48 W, or 40.32 kWh/year. Amazingly, this almost doubles the load!
Adding the two loads gets me 85.58 kWh/year total. At my current utility rate (0.06678 per kWh per month, or 0.80136 per kWh per year), this results in a cost SAVINGS of $68.58 per year. Just for the garage door opener!