Excuse me while I throttle the next person I hear bragging about the 'free' solar electricity on their RV.
It's not free you
SO STOP ADDING TO THE PROBLEM!!! (And yes, I meant to yell.)
Don't get me wrong, I'm a huge fan of solar on the RV, I've been using it on my RV's for at least 20 years; but it is not and never has been free.
Checking today's prices, in order to replicate the current solar system on my van it would cost:
180 watt solar panel: $300
Charge controller: $260
200 ah deep cycle battery $440
So, if I ignore wire costs and installation charges, my 'free' solar electricity has already cost me $1000 (No, I didn't plan that nice round number, it just worked out that way.) But I'm not done yet! Deep-cycle batteries don't last forever and since I opted for middle of the line rather than much pricier top of the line that might last twice as long (But cost and weigh nearly twice as much too!), I figure on replacing the batteries every 4 to 5 years. Lets be optimistic and say every 5 years. Let's also say the solar panel and charge controller will last 20 years, even though it's not at all clear the RV under them will. (That's a pretty conservative estimate for the panel but maybe a little optimistic for the complex charge controller.)
So over 20 years and 4 sets of batteries, assuming battery prices stay the same, my basic solar system costs will be $2320 for an annual cost of $116.
Now for a few more assumptions and a little math:
If I assume an average of 6 hours per day at a continuous 180 watts of electrical generation from my solar system, in one year I will produce 394200 watt-hours, or 394.2 kilowatt hours of electricity. (Kilowatt hours is what the electric company uses on your bill at the house.) Using my $116 per year costs that works out to pretty close to 29.4 cents per kilowatt hour. I don't know what it costs where you are but after adding in all the taxes and line charges and hookup charges and use charges and all the other crap, last month my electric co-op charged me 13.4 cents per kilowatt hour!
But wait! It gets worse!
I don't actually use all of those potential 394200 watt-hours my system is capable of generating, in fact not even close! Let's assume a really bad day where the fridge (3 amps) runs 75% of the time, and the lights (2amps), fan (2.5 amps), TV (2 amps) and laptop (3 amps) are all on for 12 hours of the day. That adds up to 168 amp-hours. Throw in 12 more amp-hours for the constant parasitic loads such as the carbon-monoxide detector and standby on the inverter then another 20 for running the microwave for 15 minutes and you have a total daily usage of 200 amp-hours. (Again a serendipitously easy number, I must be charmed, though I can think of better things to use up charm on than a little math!) So now I'm consuming a fifth of a kilowatt-hour of electricity on a really bad day. (According to the US Department of Energy the average daily household electrical consumption is more like 30 kilowatt hours!)
So now back to the calculator!:
To continue with the best case scenario theme, let's also say I live in the van 365 days a year, (Which I don't, at least not so far, but you never know when you're going to pull a bone-headed stunt that gets you thrown out of the house!!) and let's also assume I never plug into shore power and never run the van's engine, both of which will also charge the battery. So now we're assuming 100% of my van-based electrical consumption is supplied by the solar system.
In this case my true annual electrical consumption from the solar system would be on the order of 73000 watt-hours or 73 kilowatt hours.
So now, even with all those assumptions and unrealistic best-casing, a last little bit of math shows that what I'm paying for my 'free' solar electricity is a whopping $1.59 per kilowatt hour!!!!
That sounds really bad but to put it into perspective, in New Mexico State Parks it costs $4 more for an electric site than it does for a dry site. That works out to $1460 for 365 days of electric, quite a bit more than my $116 for a year's worth of solar.
By staying away from air-conditioner weather and too many microwave meals, my solar system can meet 100% of my electrical needs with complete freedom from the power grid, and let's face it, many of the best camping places are miles from the nearest electric company.
But IT'S NOT FREE!!