Learn how solar inverter is connected to the grid and how each inverter functions when connected or not connected to the grid.
Welcome to our series answering reader questions and concerns about how to cut the utility-company cord.
How can I convert my off-grid energy system to a grid-tied system?
David, Texas
We’ve all heard the adage “If it ain’t broke, don’t fix it.” So, why would someone who likely spent considerable effort and money to get off the grid later choose to tie their system back into the grid? It may seem backward, but getting back onto the grid is actually an option worth looking into – when it’s not cost-prohibitive. Because most off-grid systems are built in remote areas where bringing in distant utility power would cost more than the off-grid components, I’ll assume grid power is close enough to consider a tie-in for you.
If you’re planning to convert to grid-tied, don’t get rid of your old system. For most circumstances, an off-grid system with generator backup is the most expensive system you can build. Instead, convert to a grid-tied system with energy storage (batteries) and generator backup.
Three Types of Inverters
Three types of inverters serve the market for both grid-tied systems with battery backup and traditional grid-tied systems. Because I don’t know your current system specifications, I’ll explain all three.
- Synchronous inverters only operate with the grid and so are also called “grid-following” inverters. For safety reasons, they turn off when the grid goes down to prevent electricity from back-feeding through power lines that might have repair workers servicing them. If you have solar panels that send electricity back into the grid, you’re using synchronous inverters. Older (and some newer) off-grid systems also use synchronous inverters to convert solar energy into electricity, but, to operate correctly, they must pair with the “asynchronous” type that simulates the grid.
- Asynchronous inverters make battery-backup systems possible. They “trick” synchronous inverters into believing the grid is operating. In times when the amount of solar and stored energy aren’t sufficient, an asynchronous inverter starts up a generator until the batteries get recharged. Both synchronous and asynchronous inverters have a place in traditional off-grid systems. But if the grid is available, the better approach is to simply add an automatic transfer switch (ATS) that ensures only the grid or a generator is supplying power to the asynchronous inverter at a given time.
- Hybrid inverters are, in my view, one of the best innovations of recent times. They combine the functions of both the synchronous and the asynchronous inverters into a single unit. This reduces the cost of a system while taking up a lot less space.
Your off-grid system no doubt uses one or more of these types of inverters. Either the hybrid or the asynchronous inverter will allow you to connect directly to the grid (alongside an ATS and associated electrical components). As you get set up, choose components that’ll allow you to prioritize where your system gets its energy. I recommend that solar be your primary source of power, including for charging batteries. When solar isn’t available, prioritize batteries next. When solar isn’t available and your batteries are low, move on to grid power. (It’s cheaper to use your own established stored energy than to buy it from the grid.) A generator should be your last resort, used only if the grid goes down, solar isn’t available, and your batteries are low – because a generator is the most expensive source of electricity. In this way, adding grid power can save you money if used as a backup source.
Send Us Your Power-Full Questions
We’ll do our best to answer your questions on energy in upcoming issues. Email them to Letters@MotherEarthNews.com with “Energy Q&A” in the subject line. May all your days be filled with sunshine – even when it rains!
Hoss Boyd is founder, president, and CEO of TeraVolt Energy and a recognized solar and energy-storage expert. Learn more about TeraVolt Energy at http://TVNRG.com.
Originally published in the June/July 2025 issue of MOTHER EARTH NEWS and regularly vetted for accuracy.
