Letter Re: Advice on Photovoltaic Power Systems

Greetings! I’m a long time reader, first time writer. I have been interested in “off-grid” photovoltaic power systems as a way to generate power should the grid go down. I’m pretty well versed on electricity and concepts, but what name brands would you recommend for the main components (panels, charge controller, batteries and inverter)? Though I have heard of things like Trace, Xantrex, gel battery and pure sine wave, my practical knowledge is limited. I apologize if this has been covered before – point me in the right direction and I’ll check the archives. Also, have you ever heard of a dual setup where one could run their house the standard, “on-grid” way and then flip a switch near the breaker box to have all the outlets in the home powered by solar? Keep up the good work! – Josh in Illinois

JWR Replies: All of the major brands of monocrystaline weatherproof photovoltaic (PV) panels are essentially comparable in terms of their rated output, service life, glazing strength (impact resistance), and ability to withstand the weather. Most have similar warranties (although some are slightly better). For these reasons, PV panels should be considered a commodity, and as such, the price per watt should be the main determining factor in picking a brand. (Although if you are like me, you might prefer to buy an American-made product.)

Batteries are another commodity, at least if buy traditional lead-acid deep cycle (“golf cart” type) batteries. Because of their high shipping weight, I strongly recommend that you buy the batteries for your system from a local dealer, such as your local Interstate Batteries dealer. Be sure to do some comparison pricing before you buy. If the dealer offers a “core” credit and you are buying an entirely new system, be advised that dealers are often not particular about what you provide them for your trade in. (They are essentially just looking for a source of lead plates for recycling.) If their core refund terms are based strictly on battery weight or the combined number of Amp hours capacity, one trick is to ask around locally at venues such as Craig’s List, for free used car, truck, and tractor batteries. (Batteries that are so old and sulfated that they will no longer hold a charge.) Part-time mechanics often have a dozen or more such batteries available, free for the taking. Depending on the size of your system, if you have a strong back and aren’t afraid to get your hands dirty, this can save you several hundred dollars.

As for inverters: Inverter technology varies considerably, depending on maker. The Trace brand inverters are now sold under the Xantrex Technology name, and they still control a large portion of the market. Their major competitor in the US is Outback Power Systems, an up-and-coming company that was started by a group of former Xantrex engineers, following some serious disagreements with the Xantrex corporate management. The Outback brand holds a slight margin in inverter technology.

Charge controller technology is still advancing, but all of the major brands are roughly comparable. Just be sure to get a controller that can handle your anticipated needs, even if you eventually add a few panels. Also keep in mind that the more “bells and whistles” on a charge controller equals greater vulnerability to EMP. (They are fairly inexpensive, so it is wise to keep a spare, stored in a Faraday cage enclosure, such as a a steel ammo can.)

Ready Made Resources (one of our most loyal advertisers) offers free consulting on alternate power system system siting, load requirements/system sizing, and so forth. Be sure to take advantage of this very generous free service. They can design true “turn key” system for you that will require no upkeep other than periodic battery maintenance. A grid-tied system can be set up to provide “automatic failover””–meaning that there will be no interruption of power to your home or retreat more than at most a few moments, in the event of a power failure.You can also design a system that will allow you to sell power back to your power utility–the much-touted “meter running backwards”–depending on your local laws and power company policies.