Something I should mention is that usually it will be more costly to purchase a complete system than to go out and buy everything separately, and these complete systems can be extremely expensive. For about $300 you will be able to pick up a single solar panel that provides you with 100 W of electricity, and exactly how many you need is determined by how large of a system you are building.
For those people who are just looking to cut their electricity costs or power their house if they have a small family home and they're the only ones living there, 3 or perhaps 4 solar panels should be more than enough panels. As for individuals who have a larger home and a larger family, in order to create all the electricity you need you may possibly need between 15 and 20 panels.
A charge controller for the batteries and also a power inverter are a couple of additional items that you're going to need to purchase in order to use this electricity. It's impossible to come up with an actual cost for the power inverter because there are plenty of different sizes and the larger the inverter you need the more cash you will need to pay for it.
When all is said and done it's going to cost anything from $1000 to $1500 to get set up with a solar panel system containing three/four panels, the deep cycle batteries and other required items. You need to bear in mind that it might become very expensive if you need to get an installer to set everything up for you and, if you choose this route you should include the installation costs as a part of the investment in going 'off grid'.