Professionally installed solar power systems are too expensive these days and it could take many years to see a return on the investment. Most sites that sell 100-watt solar panels price them at around one thousand dollars. Build your own solar panel kits are not that difficult to find. Once you have a quality manual to explain what is needed and how to built the panels. A home-built solar panel costs $200 to $250 to make, so for same price as buying a 100-watt solar panel, you could make a 500-watt solar panel.