When we talk with many new RVers, the question invariably comes up: “How much would it cost me to put solar on my RV?” It’s a great question, but not one that can be answered with an off-the-cuff response because situations vary. But for illustration, we’ll draw up a sample RV solar panel system for a typical couple, based on prices for equipment available in Quartzsite, Arizona. Why there? We’ll get to that in a minute.
How Much Power?
Knowing the true cost of solar means knowing how much solar power you really need. Each RVing family has different needs; so we’ll create a fictional RVing couple, Bill and Ruth Homah. The Homahs are looking to do some boondocking in the desert this winter, away from electrical hookups. Since they’re staying in sunny Arizona, they’ll be able to count on pretty much sunny days seven days a week.
Here’s what the Homah family uses in terms of electricity:
Lighting: The family primarily uses energy efficient 12-volt fluorescent light fixtures, the typical two-tube variety. They’ll run two of those fixtures four hours a day. Since each fixture uses two amps per hour, that’s two fixtures x two amps x four hours, which equals 16 amp-hours per day.
Water: Yes sir, got to use electricity to get water in your RV. They’ll run (on average) their three-amp water pump for about 15 minutes a day. Three amps x .3 hours equals one amp hour.
Recreation: The television figures little in Bill and Ruth’s life. They tune in for about a half hour of news an evening, and maybe one hour of other viewing. That’s 1.5 hours at 3.5 amps for their set: 1.5 x 3.5 equals 5.25 amp-hours.
Staying away from the computer is more difficult. While they go to the library to get Internet access, they do spend a bit of time on computer games and preparing e-mail. They use an energy saving laptop, which they run through their portable inverter. While the laptop uses 120 watts of shore power, they’ll have to convert that over to watt hours: 120 watts times three hours daily use equals 360 watt-hours. Now they convert this watt-hour figure to something they can use when figuring solar needs. Because an inverter isn’t completely efficient, they multiply the watt-hour figure by a factor of 1.2, with a result of 144 watt-hours. Converting this to amp-hours is done by dividing watt-hours by 12. Result? Thirty amp-hours.
And the grand total is: Adding up all their daily power consumption, Bill and Ruth’s “tab” with their personal power company is a smidgen over 52 amp-hours. Where do we go from here?
Our RVing family needs to buy solar panels that will produce at least 52 amp-hours of power daily, but we’re not living in a perfect world. Another 10 percent should be added to this, as batteries are not completely efficient. So let’s say Bill and his wife need 60 amp-hours of solar power a day.
Since Bill and Ruth will make sure their solar panels point south (by tilting them when parked for extended periods), we’ll say they can expect about six hours of peak sun per day. Dividing the needed 60 amp-hours by six means they’ll need solar panels capable of producing 10 amps. They’ll also need good storage capacity for that power.
The bare minimum rule of thumb is to have battery storage capacity at least twice the production capability of your panels. Many RV solar experts suggest even more. Why so? “Save it for a cloudy day” is the answer. For this couple, that means at least 120 amp-hours of battery capacity. The Homahs settle on two six-volt deep-cycle golf cart batteries with a capacity of 232 amp-hours, meaning they’ve got close to four times the output of their solar array.
So what does it all cost? Let’s put it together.
What You Need to Buy
To meet their solar needs, Bill purchases two solar panels, a 130-watt panel, rated to produce 7.4 amps, and an 85-watt panel, rated to produce 4.5 amps. In reality, the combined total of these two panels is about 12 amps, more than they need, but better to have too much than too little. Then there are the two deep-cycle batteries. Between the two, of course, Bill will need wire, and a solar controller, a device that acts as a safety system. The controller, or regulator, prevents the batteries from being overcharged, basically cutting off the flow of electricity from the panels to the batteries when they’re fully charged. At night, the regulator prevents electricity from flowing back from the batteries and into the solar panels, unnecessarily discharging the batteries. Bill also purchases mounting and tilting hardware to keep the system up on the roof, and to allow him to tilt his panels to get the most sun available in winter, when the sun is lower on the horizon.
We base our cost estimates on price averages by dealers in the Quartzsite area. Here, with thousands of snowbirds shopping for panels, the competition among dealers is good, and there is no shipping cost associated with your purchase. Shop the Internet and compare prices when working out your own system details.
Here’s how the costs break out:
Two deep-cycle batteries $198
130-watt solar panel $575
85-watt solar panel $425
30 feet of solar wiring $37
Mounting hardware $20
25-amp solar regulator $125
Total cost $1,380
Some would gasp at that cost. However, compare the purchase and running costs of a small generator. Add in the aggravation and noise factor, and really, for many RVers, solar is an attractive option. Of course, if you shop around you may be able to find suitable used panels. For example, it’s not uncommon to find used (but in good condition) 80-watt solar panels for less than $300 each. New flexible film technology solar panels are also less than the cost of the rigid (and breakable) solar panels that most RVers are using today. We’ll discuss them in a future story.
Next month, we’ll conclude our two-part series on propane that we began in the January issue.
Russ and Tiña De Maris are authors of RV Boondocking Basics—A Guide to Living Without Hookups, which covers a full range of dry camping topics. They also provide great resources in their book, Camp Hosting USA—Your Guide to State Park Volunteering. Visit www.icanrv.com for more information.