By Russ and Tiña De Maris
You’ve seen the ad: 45 watt solar power system. Includes panels, wiring, mounts and regulator. Hurry in for less than $200. What a deal, especially for breaking into solar on the cheap! Deal? Depends. Look a little deeper.
About that 45 watt ouput: On a clear summer day it translates to about 45 amp-hours of usable power. Knowing how much power you use is the key to determining if it’s adequate. For example, an RVing couple boondocking on the desert in winter says they use the following electrical “stuff”:
•Incandescent bulbs, two to three hours a day, a total of 12 amp-hours.
•Fluorescent lamp, one to five hours a day, a total of five amp-hours.
•A nine inch color tv, two hours a day, a total of six amp-hours.
•A small furnace, one hour a day, a total of eight amp-hours.
•And miscellaneous items like a water pump, a total of two amp-hours.
Adding it up, their use works out to 33 amp-hours per day. The Harbor Freight system would be “big enough” provided each day is clear and the panels point south. But what about your use? With a laptop computer, printer, chargers for cell phones and all the other useful technology, power consumption is often much higher than our conservative example. If you need to go “bigger” you’ll need to add panels. The hangup: The solar controller included in the Harbor Freight system is already nearly “maxed out,” meaning more panels on the system equal a blown fuse.
A look at eBay reveals some 145 watt solar panels for $287 (free shipping) and a 20 amp solar controller for $64. Throw in $40 for a mounting system, a few dollars for wiring, you’ll have a system with three times the power for about twice the price. And the system is “expandable.” If you need more power, the controller is large enough to allow considerable expansion in the number of solar panels.
The Harbor Freight system has a big footprint. The 45-watt system is based on three solar panels of 15-watts each. Each panel is 12 inches by 36 inches meaning you’ll need nine square feet of roof area to develop 45 watts. Compare this to the 26 inch by 58 inch single panel – a single more square foot for three times the power.
If money is tight and you’re a low-power user, the Harbor Freight System may be just right. But if you’ll need more power, shop around.