When the solar energy cannot meet the demand, the gas generator is used as a backup charging source in the off grid system to charge the battery pack. They are also used for backup power supply in case of equipment failure and need to bypass the inverter system.
This is our advice on how to choose a generator for your off grid solar system.
As a general rule, the solar power generators should be about twice the continuous output of the inverter. For example, a 4000 Watt inverter should be paired with an 8000 watt generator.
This is because the generator needs to charge the battery while supplying power to the load (an electrical appliance that uses energy).
It is a good idea to leave some space for solar power generators by rounding it slightly, especially at higher altitudes where the generator will lose part of its power. For every 1000 feet increase in altitude, the engine may lose about 3% of its power. If your system will be installed at high altitude, please make sure that you take this into account.
Can I use a larger generator?
If you have a large load such as an air conditioner or a welding machine that is only used when solar power generators are running, a larger generator may be helpful.
We often sell 12KW and 14kw Kohler generators and our off grid systems using 4000W inverters. Larger power generation opportunities burn more fuel, but otherwise they will work normally.
Can I use a smaller generator?
Smaller solar power generators can still work, but settings usually need to be adjusted to limit the output of the battery charger. Most battery chargers allow you to adjust the AC input current strength and charging rate.
You need to match the voltage of the generator with the inverter. For example, a 120VAC generator should be paired with a 120VAC inverter / charger, while a 120 / 240VAC generator needs an inverter that outputs 120 / 240VAC.
In rare cases where you use a three-phase generator or inverter, the same rule applies: the voltage of the generator needs to match the inverter.
We know there is one exception. Magnum PAE inverter is 120 / 240VAC, but can handle 120VAC input, provided that you reduce the charging rate to 50% or less, and adjust the AC input ampere to match the size of the generator. This is useful if you need an inverter that can output 120 / 240VAC but uses a smaller generator.