Photovoltaics and sun-heated water have come a long way in the past 10 years - they're now highly efficient and can generate electricity/heat water even in poor light conditions.
You might also consider wind power if conditions near you are right. Garden turbines are quiet and efficient, as well as being cheaper than you'd think.
Have a look at sites that sell the hardware - they usually have information about the battery system you'll need, installation etc.