As the price of motor fuel shoots up, RVers are looking for ways to cut expenses. One way is by taking advantage of the beauty (and lower cost) of nature, versus staying at expensive RV resorts. For some RVers, the idea seems preposterous—go somewhere without hookups? No electric, water, sewer, television? Maybe somebody forgot to mention—recreational vehicles are self-contained. It’s true, most RVers do manage to get from RV park to RV park without trailing cords and hoses, but there are others who spend days, weeks, even months boondocking without those “shore-based” utilities.
Boondocking doesn’t mean the life of an ascetic. You won’t need to wear sandals and eat locusts, unless you really want to. Nor will you have to give up your computer, iPod, or even your television or microwave oven. Let Sol be your energy company!
Fossil Fuel Alternatives
For RVers, solar panels produce low-voltage direct current (DC) that charges up the rig batteries. The batteries store the power up for use when needed, even when the solar panels aren’t producing power. What about those “shore-power” devices like microwave ovens, computers or televisions? Most of these can be operated from stored battery power through the use of an inverter, which changes DC battery power into alternating current (AC) power that’s palatable to them.
Will solar, work for you? In most cases, yes. It comes down to how much power you use. What’s true for one RV family probably won’t hold true for the next. Space doesn’t allow us to go into detail on how to calculate how much power your own lifestyle uses, so we’ll need to use a few generalities.
How Much Power?
RVers certainly have these electrical needs in common: running the lights and water pump. Others will want to watch some TV, and if the weather is chilly, run the furnace to take the nip off. The power these devices consume is measured in amps, and adding the factor of how long they’re used equates to a figure called “amp-hours.” Before we talk about how many solar panels are needed, let’s talk about where we’ll “park” the electricity those panels produce.
A common misconception is that RV electrical devices draw their needs directly from solar panels. But the sun doesn’t shine at night—a time when you need those lights—and even at other times the panels may not produce enough power for the peak of power consumption. Enter your electrical “bank account.”
RV batteries are like a savings account for electrical power. With them you can save up the power your solar panels produce. Specially designed deep-cycle batteries are made for “house” use, that is, they can store and provide power for lights, pumps, etc. These batteries customarily produce low amounts of current over a long time. If you have a motorhome, you’ll also have one or more starting, lighting, ignition (SLI) batteries, which are designed simply to start up and operate your motorhome engine and associated operations.
An SLI battery won’t do the job of a house battery, and trying to make it do that job will quickly kill it. Deep-cycle batteries for house use are built differently, designed to be deeply discharged and recharged many, many times. SLI batteries produce a lot of current real fast—needed for starting up an engine—and then need to be quickly recharged.
Here’s why you need to know how much power you actually use. A properly designed electrical system for boondocking has the right amount of battery capacity to provide your electrical needs for at least two days, while only discharging the batteries to half of their capacity. That’s because if the sun doesn’t shine for a day, you’ll need that extra reserve to keep you going. Further, if a house battery is often discharged to less than half its capacity, its longevity will quickly be reduced.
Let’s say you’re an RVer who uses 43 amp-hours of electricity per day. You came to this conclusion by figuring out how many hours you use each given electrical device per day, multiplied the hours times the amps the device uses, then added the resulting amp-hour use for all your devices to reach your total use. If you are a 43 amp-hour user, you’ll need a battery bank with a minimum capacity of 172 amp-hours. How so? Double the use, 43 times two equals 86, and then never allow the batteries to be discharged to less than half their capacity, so double that again, 86 times two equals 172 amp-hours of storage capacity.
You probably won’t find a single deep-cycle battery that will have this kind of capacity. You’ll need two or more batteries wired properly to get the desired amount of capacity. In our example, let’s buy 12-volt batteries with a capacity of 80 amp-hours. We need three of them to meet the need, and we’ll have some extra capacity left over, as this “bank” will provide a capacity of 240 amp-hours.
Now that we know what our “bank account” looks like in terms of capacity, let’s talk about how to put “money in the bank.”
Solar: The Primary RV Alternative
How much solar power do you need? A rule of thumb says for every amp-hour of battery capacity, get a half-watt of solar panel power. In our scenario we need 120 watts of solar power for our battery bank. Solar panels need to “see” full sun. Add even a bit of a shadow across their surface, or a tiny bit of cloudiness, and energy production drops off significantly. When we consider panel production, we assume six good hours of sunshine a day. If you boondock in cloudy areas, you’ll need more solar panel muscle. Figure half of a watt per amp-hour of battery capacity.
Solar panels, left to themselves, can overcharge (read “cook”) your batteries; at night with no sun shining on them, they’ll discharge the batteries. You need an electronic “middle man” called a regulator to control the flow of electricity. Batteries full, the flow of current is cut off. At night, power is not allowed back up to the panels.
Where does that leave you in terms of dollars and cents? You can buy all the individual components, or some outfits will sell you a complete package. A glance at a popular Quartzsite, Arizona, solar retailer shows a package, including wiring, a 190-watt solar panel, mounting brackets (that allow for easy roof placement of the panel), and a regulator for less than $700. Of course, if you don’t feel comfortable installing a system, you’d have to add installation charges.
But what if your power needs are greater than our hypothetical example? Or what if your needs changed, and you need more power? The beauty of solar power is that it can be expanded with relative ease. Another panel can be mounted on the roof and wired into the existing system without much effort. Let’s say you need another 50 watts of power. You could find a suitable panel to add into the system for a little over $200. Mind you, these are new equipment prices. If you frequent heavily traveled RV hot spots like Quartzsite, Arizona, you’ll find solar dealers often have used equipment for less money. Since solar panels don’t “wear out,” a used panel is not like buying a used car—they’re far more dependable.
Over the years, RV solar equipment prices have dropped. And the beauty of the system is, one price will never change: The sun is free. n
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. Visit icanrv.com for more information.