Strike a Balance with Solar — RV Upgrades

By James Mannett

Most any household appliance can be powered from an RV battery bank, and an RV solar system can be designed to produce enough energy to replace what is consumed during a typical day. The trick is to strike a balance between the size of the solar system necessary to satisfy the daily power demand, and the needs and expectations of the user. James Mannett, a former energy industry executive and current owner of CEA Solar, answers questions from readers about the proper use of Solar Panels for RV use.

Dear James,

I have a small travel trailer with basic amenities. They include a propane/110V fridge, propane alarm, propane water heater, lighting, TV, and a Microwave Oven. When my wife and I boondock, we have to start the generator to watch TV or run the microwave. It seems like such a waste of fuel, not to mention the noise, for the short period of time we need to use regular household appliances. Is there a way to use solar on the travel trailer to run these items without breaking the bank?

Signed: Jonathan Rogers.

Dear Jonathan:

The short answer is YES. The cost of the solar system will depend on how much energy the RV appliances consume and how long you run them. First, let’s talk about the appliances, accessories, and how you use them.

A typical 32-inch flat screen TV consumes about 200 watts of power. More if it’s larger. However, a 19-inch flat screen TV that has a 12V power option consumes only 50 watts or even less. Now there are folks out there that will never give up their big screen TVs, and I understand that. For them, a larger and more costly solar system will be needed to keep up with the demand. However, if size is not important, these smaller 12V TVs cost less than $200, can plug directly into a cigarette lighter, and can be run for many hours without depleting an RV battery. And because they run on 12V, there is no need for a costly inverter. I know many RVers that use their big screens when parked in a campground when shore power is available, but bring out the smaller 12V TV when boondocking.

The microwave is another matter. Most microwave ovens consume between 800-1200 watts of power. But, because a microwave only runs for a few minutes each day, it is really a small energy user and very efficient. The trouble is getting it to operate from your battery bank. Currently I am not aware of any 12V microwave ovens. If the operation of a microwave is essential while boondocking, then I know of no other solution than to use an inverter. A simple ”modified sine wave” type would suffice, but for better operation, a ”true sine wave” type is best, but is four times the cost. Then there is the issue of installation. An improperly installed inverter can cause more harm than good. One RVer, who I know personally, recently had to replace his $1,000 inverter along with the RV’s $2,500 energy management system because the first inverter was installed improperly. Even worse, there is a real fire danger if the inverter is installed improperly. For a small travel trailer, the easiest way to avoid all of the cost and installation risk of an inverter would be to seriously assess the need to run the microwave in the first place. For the sake of the following analysis, let’s assume you have decided the microwave makes a much better bread box when dry camping than a cooking appliance.

To determine the size of the solar system, let’s examine the power demand from all of the electrical devices. (I threw in a laptop computer, even though you didn’t mention one) Also, you might be surprised to learn that even propane appliances consume some battery power, although small.

Propane Fridge	.5 amps	24 hours/day	12 amp/hours
Propane water heater	.25 amps	24 hours/day	6 amp/hours
Propane alarm (sniffer)	.25 amps	24 hours/day	6 amp/hours
3 standard RV lights	4.5 amps	4 hours/day	18 amp/hours
12V TV	4 amps	4 hours/day	16 amp/hours
Laptop Computer (w/12v adapter)	4 amps	2 hours/day	8 amp/hours
Total Power Demand:			66 amp/hours.

A typical 120W solar system will produce about 65 amp/hours of day of energy which, in your case, would be just enough to satisfy your energy demand. A smaller system could be used if you were to find ways to conserve. A roof-top system of this size would be comprised of just one solar panel. Or, if you didn’t want holes in your roof, a portable system would work well also. Either way, the cost would be somewhere in the $600-$800 range, or less than a typical generator. And a whole lot quieter!

Have questions about RV solar power? Would you like James’ RV power calculator? YWrite James Mannett at jmannett@rvsolarnow.com.