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AC Vs. DC Battery For Solar Panels

Feature image for "Ac vs DC battery for solar panels". It shows a cylindrical battery connected to multiple solar arrays.

Batteries help you maximize all the energy your solar system produces, but choosing one can be a bit of a headache. From brands to capacities, all these things can be confusing. To help you narrow down your choices, though, let’s talk about the differences between an AC and DC battery for solar panels.

If you’re in a hurry, the short answer is that DC-coupled systems are more cost-effective for new systems, while AC-coupled systems make adding battery storage systems easier for an already existing solar system.

Having said that, below is a more detailed discussion. The bullets represent the topics I’m covering, so feel free to tap on any of them to skip sections. Otherwise, let’s get started.

Let’s define what AC and DC powers are

Direct Current (DC) is the form of electricity produced by solar panels and is also the type stored in solar batteries. This makes DC essential for solar PV systems, as it is its energy’s first stage.

Alternating Current (AC), on the other hand, is the type of electricity that powers most household appliances and is used by the electrical grid. This is why an inverter is crucial, since it’s also what converts your solar panels’ DC power into its usable AC form.

Now, how do batteries come into play?

Well, you likely won’t use all the solar energy that your solar panels produce. In a sense, that’s throwing away potential savings. Having a battery storage system, however, lets you preserve your excess energy for later use. This brings us to our next point of discussion.

AC- vs. DC-coupled batteries

The fundamental difference between AC- and DC-coupled solar batteries lies in the energy conversion process.

In AC-coupled systems, DC electricity from your solar panels is converted to AC before storage. Conversely, DC-coupled solar systems store electricity in its original DC form.

There are, of course, pros and cons to each setup. So let’s dive deeper.

AC-coupled batteries: pros and cons

PROS:

  • Because the energy stored in an AC-coupled system is, well, AC, it’s also easier to integrate into pre-existing solar systems.
  • AC-coupled solar batteries operate independently from your solar PV system. This gives them more flexibility in terms of where you can install them.
  • Again, because they operate independently, they can also be used to store energy from other green sources, including wind and hydro.

CONS:

  • An AC-coupled battery tends to cost more than its DC counterpart. Partly because of the need for a separate inverter, but also because it potentially needs more maintenance.
  • The energy conversion process in AC-coupled batteries also involves more steps. This can lead to more energy loss.
  • The conversion process in AC coupling also lends itself to less efficient charging and discharging.

DC-coupled batteries: pros and cons

PROS:

  • It’s the more affordable option. Having one hybrid inverter that converts DC to AC electricity from the solar panels and the batteries is going to save you money.
  • A DC-coupled system is more efficient. The conversion process involves fewer steps, so there’s also less energy lost in the process.
  • A DC-coupled battery could potentially last longer than its counterpart. This is, again, due to the simpler conversion process, which also puts less stress on your system’s components.

CONS:

  • While it’s more affordable, it’s also only recommended for new installations.
  • You would need to invest in a hybrid inverter. This type of inverter is pricier than its conventional equivalent, but the cost of the whole system will still be cheaper than its AC-coupled cousin.

AC vs. DC solar battery: Which one is better for your home?

If the pros and cons of these batteries still leave you confused, then let’s chalk up some scenarios.

  1. Do you already have an existing solar PV system?
    • Yes. Then go with the AC battery system. It’ll be easier to retrofit into the solar system you already have, which, in this case, also makes it a more practical choice.
    • No: A DC battery system is your safe choice. Tell your trusted solar installer about your plans and call it a day.
  2. If you already have solar panels installed, what inverter do you have?
    • A hybrid inverter: Then you planned well. Go with the DC-coupled battery system.
    • Anything else: You have no choice but to go for AC battery systems. Unless, of course, you want to change your inverter to one that’s hybrid.

Ultimately, the choice between an AC vs. DC solar battery depends on your existing solar setup, energy goals, and budget. If you’re still confused, I recommend speaking with a professional.

Conclusion

To summarize, AC-coupled battery systems need their own inverter. For this reason, they’re also easier to integrate if you already have solar panels. A DC-coupled system, on the other hand, uses the same hybrid inverter as your solar panels, making it a more affordable choice, particularly for new installations.

If you need help deciding, or even if you’ve already made a decision, we have a network of pre-vetted solar installers that can help. Just let us know, and we’ll send 3 FREE quotes your way.