If you want to be completely self-sufficient in terms of energy generation, you must be prepared for times when the sun is covered for many days by clouds and your solar panels are left with insufficient light to charge the batteries fully.

This is where your solar system’s backup generator comes in handy!

Remember, while buying a generator is a significant financial commitment it is a worthwhile investment to provide backup power for your off-grid energy system!

So we’ve hunted down all the useful information you’ll need to be sure you have the correct size generator for your off-grid farm!

industrial diesel generator

But how do you calculate what size generator you’ll need?

When selecting a backup generator for your solar system, there are several factors to consider to ensure that it has the power needed to meet your demands.

The correct size generator will be determined by how it will be used in your solar power system and how much power you want for your off-grid home.

Generator output

As a general guideline, the generator should be at least 2 times the continuous output of the inverter. A 4,000-watt inverter, for example, should be connected with an 8,000-watt generator.

This is due to the fact that the generator must charge batteries while also powering other loads, such as your household appliances using up energy when operating.

If the load is 4,000 watts and the charger is 60 amps at 48 volts, the total continuous power is roughly 7 kW:

60 amps x 48 volts = 2,880 watts plus 4,000 watts equals 6,880 watts

A minimum generator size of 8kW would be sufficient to power the loads while also charging the battery bank. It’s a good idea to round up a little to give the generator some breathing room and have some excess capacity in case you need more power.

This is especially useful at higher elevations when the generator output could be reduced, depending on what generator you are using.

For every 1,000 feet increase in altitude, conventional generators lose about 3% of their output. If your system will be put at a higher altitude, make sure to account for this!


Generator power is often given as kVA.

This is a measurement of the absolute power available if a system was 100% fuel-efficient. However, this is unlikely to be achieved as some energy consumption will occur when the machine operates.

So when you see the power output of a generator it will often be shown in kVA, and you’ll need to calculate what that means to match the consumption of your off-grid home.

Is bigger better?

installing an emergency generator

What is the best-sized generator for off-grid solar systems?

Bigger generators are ideal for homes or businesses with heavy energy loads.

This can be very useful especially when you have heavy loads that will only be used when the generator is running, such as an air conditioner or a welding machine. You will also want to ensure all your power requirements can be covered by the generator during power outages.

For off-grid systems, a 4000w inverter is often sufficient for 12kW and 14kW generators. Remember that larger conventional generators, like diesel generators, consume more fuel than smaller generators so you may not want to choose one that is very much larger than your requirements.

Will a smaller generator be preferable?

Smaller generators can still be used, but the output of the battery charger must be limited by modifying the settings.

The AC input amperage and charge rate may usually be adjusted on most battery chargers. You’ll need to match the inverter’s voltage to that of the generator.

alternative energy

The same criteria apply whether you’re using a three-phase generator or inverter: the generator’s voltage must equal the inverter’s voltage. It requires you to alter the parameters to control the battery charger’s power in order for them to work properly.

So, what is the ideal generator size for a small home?

The average modest home uses 2.86kWh of electricity, and if we add a 20% safety buffer we can round off to 3.5kWh for our calculations. To determine the size of generator required for this type of power consumption, divide this number by 0.8.

4.375kVA = 3.5kWh / 0.8

It can be rounded up to 4.5kVa, which is the generator size required to power your home. The extra safety features incorporated supplied enough increased power to recharge the battery and power your home at the same time.

How about a medium-sized home?

A medium-sized home’s energy use is around 6.5kWh, and with the 20% safety margin, this rises to 7.8kWh, which we’ll round up to 8kWh. When we use the 0.8 power factor in the same computation, we get the following result.

10 kVA = 8kWh / 0.8

A 10kVA generator would be required to power a medium-sized residence and charge the solar batteries.

For a large-sized home

A typical large-sized home consumes 17.8kWh of energy, which is increased by 20% to 21.35kWh, which we will round up to 22kWh. We repeat the computation to determine the generator size that would be required for a residence of this size.

27.5kVA = 22kWh / 0.8

The 27.5kVA result can be rounded up to a 30kVA generator for powering your home and charging your solar battery.

Solar system components for off-grid applications

To achieve maximum performance, the off-grid solar system includes four components.

Photovoltaic panels

construction worker installing solar panels

Solar panels are physically fixed on a mounting frame to generate DC electricity, which is then routed through the charge controller and stored in the battery bank.

The size and output of a solar array are determined by the quantity of sunshine available in the area, as well as energy consumption requirements and available roof space.

Charge controllers for solar panels

The solar charge controller, also known as a battery charger, is essential for the battery to preserve energy. Its primary role is to regulate the voltage and current that the solar battery receives in order to prevent overcharging or breakage.

Charge controllers have two main functions: they prevent the battery from overcharging and stop the reverse current flow from the batteries to the photovoltaic panel at night.

Other factors to look for when buying off-grid generators

It has a 2-wire start

The automated generator start function for off-grid generators linked with solar power systems requires 2-wire start capabilities. When the voltage on your batteries falls below a particular level, the AGS activates, causing the generator to start and recharge your battery bank. It’s important to note that a 2-wire start is not the same as an electric start.

Some generators will have an electric start/stop button, but they won’t work with a 2-wire signal, which means the inverter won’t be able to connect with the generator to activate the AGS mechanism.

Double-check its warranty

Off-grid and prime power applications aren’t covered by most generator warranties. Make sure the generator’s guarantee allows it to be used off the grid.

Why should you utilize off-grid solar systems?

Actually, both types of solar systems have their own set of benefits and drawbacks.

As a result, it is entirely up to you to select the best option for your power supply requirements. The numerous advantages of employing off-grid solar energy in your home cannot be overstated, particularly because it will set you apart from other homeowners during a power outage!

solar power regulator

To make things easier for you, here are some of the reasons why an off-grid solar system is better for your home and workplace.

Helps clean up the environment

You should go solar if you want to keep your surroundings green and clean at all times. Many businesses provide electricity through environmentally dangerous methods.

Using an off-grid solar system will ensure that you have access to pure solar energy while reducing your environmental impact.

Monthly rates are low

You will be helping the environment while also saving money in the long run if you use off-grid solar systems!

You won’t have to be concerned about exorbitant monthly rates or rising electricity costs. The average monthly cost of solar energy for homes is around $84, but this varies greatly based on a variety of factors.

Installation is simple

Since the equipment required to run off-grid solar systems does not rely on the grid to function, the installation process is fairly simple. Complicated infrastructure or connections are not required. All that is required for you to install this system is a working knowledge of basic tools. A professional can guide you and show you the ropes if you are not sure.

In addition, there is no need to go through the costly trenching process that is often necessary when joining solar energy to the grid.

Despite power disruptions, there is always light

You will be in a blackout if there is a power loss caused by a storm and you are grid-tied! You will be powerless until the power is restored because most home and workplace appliances operate on electricity. Natural disasters have wreaked havoc in several areas of the United States in recent years, necessitating the need for a solid backup.

This is accomplished by storing energy in batteries so that your home is always powered, regardless of the weather!

A better way to reside in rural areas

One of the issues that residents in rural areas confront is the high cost of connecting to the main electrical grid, which is frequently expensive and time-consuming.

You can save money by using off-grid technologies, especially if you live distant from the main electricity grid. You will also be able to generate clean electricity wherever you want to live!

solar panel on hillside

This will save you time and money while also guaranteeing that you have a reliable power supply. By moving off-grid, you can avoid the hassle of overcoming the obstacles that come with being grid-tied.

Take away

Keep the following in consideration while looking for a generator to power your off-grid solar system:

  • The output of your generator should be at least twice that of your inverter
  • Match the voltage of the generator to the voltage of the inverter
  • Off-grid generators must be covered by a warranty
  • To work automatically with a solar system, a 2-wire start is required
  • 3600 RPM generators are less expensive, whereas 1800 RPM generators are more expensive initially but last longer and are more effective