Can You Add Battery Storage to an Existing Solar PV System? Leave a comment

Yes. In many cases you can add battery storage to a solar PV system that has already been installed.

The main question is not whether a battery can be added, but how it should be connected. That depends on your existing inverter, the age and type of the solar system, whether you want to retain the existing inverter and whether backup power is part of the plan.

Option 1: AC-coupled battery storage

An AC-coupled battery system has its own battery inverter. Your existing solar inverter can normally remain in place, so the battery operates alongside the solar system rather than replacing it.

This is often a straightforward route for retrofits, particularly where the existing solar system is working well and there is no good reason to replace its inverter.

It can also be useful on older systems because the battery is electrically separate from the PV inverter. The exact design still needs to be checked against the property, metering arrangement and any existing generation scheme.

Option 2: Replace the solar inverter with a hybrid inverter

Another option is to replace the existing solar inverter with a compatible hybrid inverter and connect the battery directly to it.

This can produce a neat integrated system, but it involves changing more of the original solar installation. Whether that is worthwhile depends on the age of the current inverter, the panels already fitted and the battery platform you want to use.

If an older inverter is approaching the point where replacement is sensible anyway, a hybrid upgrade can be worth considering. If the existing inverter is relatively new and performing well, AC coupling may be the simpler route.

What if you have a zappi or eddi?

Third-party batteries can coexist with myenergi equipment, but the system needs to be configured so the battery and devices do not unintentionally compete with each other.

myenergi’s own guidance explains options such as export margin settings and, for standalone AC-coupled batteries, using an additional CT so the system can recognise battery power flow and avoid draining the battery when that is not wanted.

See myenergi’s guide to using a third-party battery for the current manufacturer guidance.

What information do we normally need?

For a retrofit battery enquiry, the most useful starting information is:

• the make and model of your existing solar inverter;
• the approximate solar array size;
• a photo of the consumer unit;
• a photo of the proposed battery/inverter location;
• your approximate annual or daily electricity use;
• whether backup power is important to you.

From there we can work out whether an AC-coupled system, a hybrid replacement or another arrangement is the most sensible route.

You can also use our Battery Storage System Builder to narrow down suitable options, or see our Solar & Battery Installation page if you want a fully installed system.

Sources: Energy Saving Trust — Battery storage (updated August 2026) and myenergi — Using a third-party battery with myenergi devices. Information checked September 2026.