A battery and Inverter subsystem allows the generator to run when required for large loads and battery charging, while the inverter powers smaller loads when the generator is off. When shopping for an alternative energy system, it will eventually come down to your site and what resources are available for generation of energy. Generally, everyone has access to the sun. It is the simplest form of alternative energy, it's also the most expensive. Wind can be harnessed to produce large amounts of energy.
Wind energy is very site specific.
If you do not have a good wind site to start with, results will be disappointing no matter what you do. Micro-hydro harnesses the energy in falling water and produces electricity. It is the most cost effective of all alternative energy. If you have a source of running water, you simply must examine it's potential. Most systems are hybrid in design - they use more than one charging source, often varying with the seasons.