What is AC Coupling?
A battery setup where the battery has its own inverter and connects on the AC side, ideal for retrofits.
Quick Answer
AC coupling is the usual choice in the UK when adding a battery to an older solar array, because it works with almost any existing inverter. Batteries like the Tesla Powerwall and many retrofit systems are AC-coupled. For a brand-new solar-plus-battery install, a DC-coupled hybrid inverter is often slightly more efficient.
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AC Coupling Explained
AC coupling is a way of connecting a solar battery where the battery has its own built-in inverter and joins the system on the AC (mains) side, alongside the existing solar inverter. Solar energy is converted from DC to AC by the solar inverter, then converted back to DC to charge the battery, and to AC again when discharged. The extra conversions cost a little efficiency, but AC coupling makes it easy to add a battery to an existing solar system without replacing the inverter.
How Does AC Coupling Work in the UK?
AC coupling is the usual choice in the UK when adding a battery to an older solar array, because it works with almost any existing inverter. Batteries like the Tesla Powerwall and many retrofit systems are AC-coupled. For a brand-new solar-plus-battery install, a DC-coupled hybrid inverter is often slightly more efficient.
Frequently Asked Questions
What is the difference between AC and DC coupled batteries?
An AC-coupled battery has its own inverter and connects on the mains side, making it easy to retrofit to any existing solar system. A DC-coupled battery shares a single hybrid inverter with the panels, which is slightly more efficient but usually means installing it together with the solar.
Is AC coupling good for adding a battery to existing solar?
Yes. AC coupling is the most common way to retrofit a battery in the UK because it works with almost any existing solar inverter, so you do not need to replace it. The trade-off is a small efficiency loss from the extra DC-to-AC conversions.
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John Rooney is the founder of Solar Info and has been covering the UK solar energy market since 2023. He researches every battery and inverter brand against manufacturer datasheets, MCS and Ofgem data, and feedback from the MCS-certified installers in our directory before publishing.