The normal off-grid system contains a battery bank and some kind of backup charging system. The backup charging system can be diesel, biodiesel, propane, or gas powered motor/generator. The solar/wind reduces the frequency of the backup generator run and its time. The combination of a generator, battery bank, and inverter is called a Genverter system.
Every off-grid power setup is a Genverter system PLUS free charging sources like wind, sun, and hydro. So for example, comparing a straight diesel only power system to a diesel powered Genverter system is easy. The generator only solution must be run, just to power a 20W light when needed, and all the excess power is wasted. When the other equipment for a Genverter is added, you only run the generator to charge batteries, otherwise power is available 24/7.
Hope this helps clarify things for you.