I went on energystar [dot] gov and used their product finder to find the lowest "annual energy use" compact refrigerator. For my use, that turned out to be the FURRION - FCR43ACA-BL which has an estimated 151 kWh/yr annual energy usage rating. I then wanted to run this off of one solar panel. Now I'm new to solar, so I also need a battery, an inverter, and a charge controller.

What I'd like to know is after expenses

(1) solar panel
(2) battery
(3) inverter
(4) charge controller

at what point, in practice, does this pay itself off compared to PG&E at $0.12/kWh? I mean, if 1-4 costs, say, $300, then if the fridge is costing me $18.12/yr from PG&E to run, then does that mean it takes 16.5 years to pay off? If so, then can I get 1-4 low enough to make the investment worth it? Paying it off in 3-4 years seems worth it but 1-4 isn't going to cost $72.48.

  • Hrm...I wonder if this isn't the only approach to a solar fridge...thermal solar + intermittent absorption comes to mind... – ThreePhaseEel Oct 27 '17 at 3:12
  • @ThreePhaseEel, what, like this? – user74623 Oct 27 '17 at 3:40
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    This reminds me of the guy who used to run to work behind the bus to save the bus fare. He decided to run behind a taxi to save more money. :-) Solar is expensive energy as an investment. Plus, if you're using it for food that can spoil, you need to keep it running for the longest expected period of no sunshine (a stormy day with night on either side is a long time). – fixer1234 Oct 27 '17 at 4:09
  • @fixer1234, oh, no, not at all. I'm just testing locally for a commercial application, if that makes sense. – user74623 Oct 27 '17 at 4:52
  • You seem to have answered your own question: By your criteria the investment is worthwhile when 1-4 (incl. installation etc) cost < $72. It is unclear to me what you expect an answer to look like. – RedGrittyBrick Oct 27 '17 at 10:02

You've ignored two major factors:

Batteries don't live forever, and require maintenance as well as periodic replacement - more so if they are abused (typical when people save money on batteries and then over-discharge them.) This is one reason that "grid-tied" solar is far more common where the grid is available - it eliminates the battery storage and its related costs and labor costs.

The second is harder for most people to grasp - if you paid the $19 dollars to run the fridge, and invested the rest of the $300, how much would that investment yield in 16.5 years? It's a little hard to know for certain since guaranteed bank interest is in the doldrums, but typical returns for sensible investments are near 5% - which would nearly pay your next year's power bill, and if there was any growth in the investment, you might end up making more per year than the power bill comes to.

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  • Good point, particularly your second point, which, I mean, give "most people" a break, it's not that hard to grasp. It's weighing the benefits between having physical capital or paying for a service with invested interest. – user74623 Oct 27 '17 at 17:51