Travis asked in EnvironmentGreen Living · 7 years ago

how much solar power do i need for my electronics?

I plan on living out a van for camping for about 2 months and more to come such as trips and what now. I am wondering how to get a setup or electricity inside.

If i had 1 deep cycle battery(12v 120Amp hours) with 2x 100 watt solar panels(12v) hooked up to a solar charges and power inverter. how many amp hours will i produce in a day. also will this be enough to run these things

small energy efficient 24 inch led tv for 2-3 hours(60kwh a year)

1.7 in cu.ft fridge(115v on lowest setting, i assume around 60 watts)

a laptop charger for 3-4 hours(3.5 amps)

microwave once for about 3 minutes

and a phone charger for 10 hours

just curious if i will have enough power, more than enough or do i need more, if i need more then what will i need


Thank you so much for the advice. A couple things though if you don't mind.aren't mini fridges 110v, and what about a 700watt microwave, will that work? I saw a mini fridge that consumed 315kwh a year.

3 Answers

  • 7 years ago
    Favorite Answer

    Hey Travis, this project is difficult to nail down exactly, but I'll give you some rough numbers. The TV probably uses 30 to 40 watts, at 2.5 hours per day, with a 87% efficient inverter, will need around 10 amp hours per day from the battery. The laptop at 3.5 amps, which I assume is the current draw on the low voltage side of its 15 volt transformer, for 3.5 hours will need another 12 to 15 amp hours at 12 volts. The phone charger is almost negligible, but we'll call it 1 amp hour. All that, which are your "electronic" loads can easily be handled by 1 of your 100 watt panels with a suitable battery and charge controller if you have sun every couple days. The fridge is a killer. I don't know if I buy the 60 watts, more like 90 for even a small one, but even if it is 60, at 10 hours per 24 hour period, will eat over 50 amp hours at 12 volts, maybe more in warm weather. Even with 200 watts of solar, which is 11 amps at an 18 volt open circuit voltage panel set (typical for 12 volt systems), the best you'll get on a clear sunny day is 50 amp hours. One cloudy day with the fridge and you have no battery power all night.

    The microwave has its own problem. At 3 minutes, even for 1200 watts for a large one, it is only using 2 amp hours, but you'll need about 2000 watts of inverter to start it up, even for 1 second, so you are overbuying for one item, and the larger inverter will use more power at idle than an inexpensive 750 watt car model.

    Does the motor on the van run? That could augment your power on cloudy days or at night, but you'll be running it an hour or two each day. I like cold drinks, ice, and refrigerated food as much as the next guy, but the fridge is your Achilles heal here. John Vigor, in his book "Everything I wish I know about sailing before I bought my boat" addresses this pretty well. We have setups like this in several places, a barn, campground and my truck. If you used two golf cart batteries, specifically Trojan T-105, hooked in series for 12 volts, you would have 220 amp hours of storage for the same money, and they would last longer than one 12 volt model. Then if you used LED lighting (you didn't list any lighting), a car model cell phone charger, a 750 watt inverter from an autoparts store, your TV and laptop only when needed, those 2 panels would work great, and you might need the motor once or twice a week is all. There are always cloudy rainy periods, panels produce very little then. It's a doable project, but you either have to lose the fridge and go with an RV model 12 volt microwave, or get a huge inverter and more like 500 watts of solar. Don't take my word for it though, look at the yellow energy label in a small fridge for annual KWH usage. Multiply by 1000, then divide by 365 for daily watthours, then divide by 12 for voltage, that will give you minimum amp hours per day, it is staggering. I'll list some sources below, good luck, and take care, Rudydoo

    Yes, virtually all mini fridges I have seen are 110 volt. At 315 Kwh per year, is .92 per day, plus losses from the inverter, your battery has to deliver 80 amp hours per day at 12 volts to provide the .92 kWh necessary at 110 volts for the fridge. That is about twice your total production on a clear sunny day with 200 watts of solar. Most calculators at solar websites would recommend 500 to 600 watts solar for that. The 700 micro is good, we have a 750 here, but it will require higher start up power, about a 1200 watt inverter. You can find them for $120 - 180 if you shop around. A 750 watt inverter can be found easier for about half the price, popular size. Good luck.

    Source(s): Home Power Magazine, Midwest Reneewable Energy Association, MREA.ORG: Solar Energy International,
  • 4 years ago

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    7 years ago

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