An off-grid system supplies electricity in a place where there is no utility power available.
This could be to power a remote cabin, a large off-grid residence, or a single device such as a water pump, gate opener, or other type of load.
The off-grid power supply must be capable of providing sufficient power year-round, unless the need for power is seasonal.
The typical main source of power for an offgrid system is solar (PV) modules. Power generated during the day from the modules is typically stored in a battery unless the need for the power coincides with the sunny times of the day, for example a well pump to fill a tank.
For an offgrid full-time residence, a system powered solely by solar modules will be insufficient in the winter time in our area due to the shorter days and cloudy/rainy weather we usually experience. Therefore, a fossil fuel powered generator (propane or diesel) is typically used as a secondary source of power. A well-designed system should be able to operate 8-9 months of the year without the generator. The generator becomes critical for the remaining months.
The key to correctly sizing an off-grid system is to calculate (or record) the average daily electrical usage for the system. The unit of measure for electrical usage is the kilo-watt hours (kWh). The average daily electrical usage may change with the seasons, so that should be take into account.
Radiant Solar uses an in-house spreadsheet that we have designed for sizing an off-grid system. Keep in mind that the occupants of an off-grid residence ultimately determine the viability of the system by their usage patterns.