How To Connect A Generator To A Solar System? Best Detailed Guide [2021]

If you have a solar panel at your home, you will know that there will be days when the sun isn’t shining or your solar batteries may be low.

At this time, the option that you have is to charge your solar batteries using generators that are fueled by fossil fuels.

Now you must be thinking of How to Connect A Generator To A Solar System. So here is the answer.

Connecting a generator to a solar system is easy. All you need to do is to follow these steps one by one. First set bulk charge at 10% of the battery bank’s C20 rate, then program the correct bulk voltage onto your charger/inverter, later program the absorption charge time on your charger/inverter, and lastly create a system that will shut down the generator after reaching the bulk voltage.

All these steps are explained in great detailed below. Follow each step properly as messing with electric equipments is not a fun and one single mistake can ruin all your connection.

Creating electricity with a generator can be a costly affair and may cost anywhere from $2.50 t0 $5.00 per kilowatt-hour compared to the other $.05 to $.60 per kilowatt-hour for the different utility charges.

How To Connect A Generator To A Solar System

Steps To Connect A Generator To Solar System

1. Bulk Charge At 10% Of The Battery Bank’s C20 Rate

The first step to set your system to an existing solar battery is to program your generator/battery/inverter to a minimum charge of 10% of the C20 AH rating of your battery’s bank.

If you have a hard time figuring out the C20 amp-hour (AH) rating of your battery bank, go through your battery manufacturer’s handbook.

After figuring out the C20 AH rating, take that rating and then multiply it by 10 or 10%, and you will get the current setting bulk charge.

There are some manufacturers that will permit up to 15%, but that is defined at the C3 AH rating. To get the most of your dollars, try to get at least 10% of the AH rating of your battery bank.

Sometimes, there will be a situation when you cannot do this, because of the small size of the charger or the small generator. At this point, you charge it a lower current, but it won’t be efficient.

If you go beyond the 10%, then you are risking the damage of your batteries due to over-gassing and overheating.

If you have a bigger and larger generator/charger, then 45 amps will be the minimum target change rate. Current lower than this will mean excess run time for your generator and fuel consumption, and any more will damage your batteries.

2. Program The Correct Bulk Voltage Onto Your Charger/Inverter

Always consult with the manufacturer of the battery for the appropriate bulk voltage setting.

You should be careful, because there are some manufacturers who list the bulk voltage settings in following ways.

  • The absorption voltage (same thing as bulk voltage).
  • The bulk/absorption voltage (same thing as bulk voltage).
  • The bulk voltage as a range (i.e. 2.35-2.45 volts per cell).
  • The bulk voltage per cell.
  • The bulk voltage per battery.
  • The daily charge voltage (same thing as bulk voltage).

The terms that are stated above like daily charge, absorption, and bulk voltage are all referring to the bulk voltage settings.

If the bulk voltage is listed on the handbook as per cell, then think of each of the cell as being two volts.

  • A 6-volt battery or battery bank will have three cells.
  • An 8-volt battery or battery bank will have four cells.
  • A 12-volt battery or battery bank will have six cells.
  • A 24-volt battery or battery bank will have twelve cells.
  • A 48-volt battery or battery bank will have twenty-four cells.

Once you understand how many cells are present, all you have to do is to multiply the volts per cell and the total number of cells that are present.

3. Program The Absorption Charge Time On Your Charger/Inverter

Although this is not a necessary step, we must discuss it and we normally would not take use of the absorption charge to add extra to your 20% of the battery bank.

Most of the chargers will need a time set for completing the program for the bulk charge. The normal setting would be for 4 hours. This will be a correct backup if your automatic generator fails or malfunctions.

The whole process will take about 4 hours (if you are using 10% of C20) to completely charge your bank to its full state after reaching the bulk voltage.

4. Create A System That Will Shut Down The Generator After Reaching The Bulk Voltage

Correctly bulk charging your battery bank will take it up to 80% of its total State of Charge (SOC). If you use your bulk charger for any other purpose, it will waste fuel and will be inefficient.

If you want to add an extra 20% to your batteries you can complete the float charge and absorption charge but it will be a waste of fuel.

It would be more efficient if you could make your generator as your charger and your wind, solar a micro-hydro to increase the charge of the batteries to 100% SOC (State of Charge).

Almost all of the high-end chargers/inverter controllers of charge will have a programmable relay driver that can help you to stop the generator from reaching the bulk voltage. To learn how to set this up you should refer to your generator’s manual.

By following these step, you will get the most energy input for by using very little fuel.

How To Connect A Generator To A Solar System: FAQs

Can a generator charge solar batteries?

Yes, A generator can easily charge solar batteries as most of the modern off-grid solar may not be able to meet the entire need of the property from solar energy alone and is often paired with a generator. Gas generators are used as a backup source of charging. They can also be used if the inverter equipment fails and bypassing is required for the system.

If you have solar panels, do you pay for electricity?

Yes, you will receive the electricity bill, but you won’t be asked to pay anything because you consumed no electricity from your end. However, sometimes you may have to pay the electricity bill if your solar panels were not working. For example, due to a bad weather condition, they weren’t charged properly, and you utilized electricity from the supply.

Can i install solar panels on my roof?

Yes, you can install solar panel on the roof of your house which may have a life of around 20-25 years, but before that, you should check the state of your roof, if your roof is dilapidated then you must first repair your roof or then you must repair the roof and then install the solar panels. Also, you must check if there is enough space on your roof, for the panel to absorb enough sunlight.


Connecting a generator to a solar panel is necessary for conditions when your solar panels cannot get the necessary output for your needs. Connecting the generator helps keep your lights on especially in bad weather.

I hope this guide will clear all your important queries related to How To Connect A Generator To A Solar System. Feel free to ask anything if you still have more queries. I will try to answer your queries ASAP.

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