So, let´s look at your specification and how energy can get lost within your solar panel system.
Drawing Up Your Specification
Once you´ve taken all your devices and worked out how many hours you use them for, and done the math, you´ll have the total energy in Watt-hours required to make yourself happy with solar energy. There is some useful advice on this page regarding solar panel wattages and battery sizes. To be very broadly general, most panels will put out their maximum output for five hours per day.
Next, we should talk about the limitations of the technology, how to get the best out of it and match your needs.
One thing to bear in mind with all solar panels is that their stated output is calculated under test conditions. The actual output is affected by latitude, shading, haze, cloud, atmospheric dust, the time of day, and other factors, including which brand of panel you use. If you´re in a very hot place, your panel can actually produce less energy—about 5% less for every 10ºC rise in temperature over 25ºC! And if your panel is old, it´s less likely to generate energy well.
Cables are another area where you can lose energy due to resistance. To minimize cable losses, large core cables are needed. Longer cable needs to be even fatter than shorter ones. Buy marine-grade electrical wire.
Shading is one of the easiest ways to lose power from a panel. Even the shady stripe from a rope can wipe out a large amount of the output. This is because the shaded cell acts as a sink for the power produced by all the other cells. Cover the panel by 10%, and your output will drop to zero (unless you have an amorphous panel)!
Regulators protect your batteries, but they also inevitably lead to losses. MPPT-type regulators, such as a Victron 75/15, which can be bought for under $150, have both advantages and disadvantages. It´s recommended that you invest in one, to protect your battery or batteries, although it will account for some energy loss when the circumstances call for it.
So how do all these losses total up? You´re looking at an average of 40% loss. And on a good day, you´ll lose around 25%. These loses are unavoidable, but minimizing them is worth your while!
In Part 4, we´re going to look at tilting your panels, where to buy them and the tools you´ll need for the installation.