AC-coupled vs DC-coupled: how a home battery connects

There are two ways to add a battery to a home electrical system: on the AC side (AC-coupled) or on the DC side (DC-coupled, through a hybrid inverter). Which suits you depends mostly on what you already have – an existing solar system with a working inverter, or a new installation. This guide sets out the differences and what your installer has to arrange with the network operator (DNO) in Great Britain.

How power flows

Solar panels and batteries work on direct current (DC); your home and the grid use alternating current (AC). Every conversion between the two costs a few per cent.

AC-coupled: the retrofit option

An AC-coupled battery has its own inverter and connects to a circuit in your consumer unit like a large appliance. A meter or current clamp at the incoming supply tells it when you are exporting and when you are importing.

Pros

• Works with any existing solar system, whatever the inverter brand.
• Battery and solar are independent, so replacing or adding either is simpler.
• Works without solar at all – for example to shift grid power on a time-of-use tariff.

Cons

• Solar power is converted twice more before it is stored.
• Two inverters: more wall space and more standby consumption.

DC-coupled: the hybrid inverter

A hybrid inverter has inputs for both panels and battery, so solar power can charge the battery directly. One box manages panels, battery and grid.

Pros

• Fewer conversions for stored solar energy.
• One inverter, one app, one point of contact.
• Many hybrid inverters offer a backup (EPS) output.

Cons

• Battery and inverter must be compatible – manufacturers publish compatibility lists, and high-voltage batteries only work with inverters designed for that voltage range.
• If your solar inverter is young and healthy, you pay to replace something that still works.

Does coupling decide efficiency?

Fewer conversions help in theory, but system quality matters more in practice. HTW Berlin tests AC- and DC-coupled systems in separate categories; in the 10 kW class its 2026 System Performance Index ranged from 89.3% to 97% ¹. A good AC system can beat a mediocre DC one, so look at measured efficiency and standby draw rather than the coupling alone. More in usable vs nominal capacity.

What our database shows

Of the 39 home batteries in our database, 10 state their coupling explicitly: 8 DC-coupled and 2 AC-coupled. For the rest, the inverter you choose usually decides; many high-voltage batteries are designed for a hybrid inverter from the same or a compatible manufacturer.

Backup power: for 24 of the 39 models the manufacturer lists a backup function. That does not mean your whole house stays on in a power cut. Usually a separate backup circuit or changeover switch is needed, sometimes an extra module. Ask your installer which circuits will stay live and how quickly it switches over. See our list of home batteries with backup power.

Grid connection: G98 and G99

In Great Britain, DNOs treat energy storage as demand when it imports and generation when it exports ². So a battery counts towards the generation limits, whether it sits on the AC or the DC side ²:

This matters when adding a battery to existing solar: a 3.68 kW solar system that was fine under G98 can move into G99 once a battery is added. Plan for the DNO’s response time.

Choosing an installer

The Energy Saving Trust recommends getting at least three quotes from MCS-certified installers ³. An MCS installer handles the DNO paperwork and follows the MCS battery storage standard.

Which should you choose?

• Existing solar with a working inverter: AC-coupled battery.
• New system, or inverter due for replacement: hybrid inverter with a compatible DC battery.
• Backup matters: a hybrid system with an EPS or whole-home backup option; check switchover time and which circuits are covered.
• No solar, but a time-of-use tariff: an AC-coupled battery is the simplest route – see home batteries and time-of-use tariffs.