Back-up generators

A generator is an essential part of any domestic scale solar system. Although it is theoretically possible to design a system with enough battery storage capacity to see you through a prolonged period of cloudy weather, the cost of such a system is just too high. Typically a battery bank is sized to store enough energy to last the household for 3 days without any sun.

Back-up generators can run on a variety of different fuels such as petrol, diesel and bottled gas. Each fuel type has its advantages and disadvantages and to some extent the generator's output governs the type of fuel used.

Sizing a generator is generally straightforward and involves determining the size of the load that the house will draw from the generator and adding that to the power needed to re-charge the batteries. This total should be no more than 75% of the generator's output to ensure that it is not run too hard and to allow for some extra power now and then if necessary.

More advanced (and therefore expensive!) generators have the ability to be started and stopped by your solar system without any human intervention. These are used on installations where automatic generator back-up is desired/required.