Wall-mounted home battery in utility room or garage

Retrofit-friendly battery storage

AC Coupled Battery Storage — Add a Battery to Your Existing Solar System

If you've already got solar panels, you don't need to replace your inverter to add a battery. AC coupled battery storage works alongside your existing solar setup — and it works as a standalone unit if you don't have solar at all.

Get a Free Quote Call 07516 762540

From £2,800 Standalone battery installed

0% VAT Until March 2027

Any solar Compatible with all brands

5-8 yrs Typical payback (no solar)

MCS & NAPIT Certified Insurance & warranty valid

5-Star Rated Across Google & Trustpilot

Free Survey Within 48 hours

Based in Milton Keynes Genuinely local

0% VAT Until March 2027

What is AC coupling?

In a normal "DC coupled" solar + battery setup, the panels, battery and grid all share a single hybrid inverter. That works brilliantly when you're installing everything new on the same day — but it's a problem if you already have solar and want to add a battery later.

An AC coupled battery system is the answer. Your existing solar inverter stays exactly as it is, and we add a separate battery inverter that charges the battery from the AC side of the system. No need to replace, upgrade or rewire your solar inverter.

It's also the right choice if you want a battery without solar at all — the same hardware can charge from the grid on a cheap overnight tariff and discharge during peak hours.

AC vs DC coupled — quick comparison

Most homeowners don't need to dig into the technical detail — but if you're choosing between a retrofit and a new combined system, this matters. Here's how they compare on the factors that affect your decision:

Factor	AC Coupled	DC Coupled (Hybrid)
Best for retrofit	✅ Yes	❌ Means replacing your existing solar inverter
Best for new install (solar + battery same day)	OK	✅ Slightly more efficient
Standalone battery (no solar)	✅ Works as-is	❌ Designed around solar
Round-trip efficiency	~90%	~94%
Typical retrofit cost premium	+£200-£600 vs DC retrofit	Higher — full inverter swap
Mix-and-match brands	✅ Any solar inverter, any battery	❌ Must match brand/system

Standalone battery (no solar required)

An AC coupled battery doesn't need solar to be useful. You can install one on its own and use it to:

Charge from cheap overnight rates — Octopus Agile or Intelligent Octopus at 5-7p/kWh, then discharge during the day at 24p+
Provide backup power during outages (with the right hardware — we'll specify if you want this)
Be ready for solar later — when you do add panels, the battery is already in place

Typical payback for a standalone grid-charged battery on Octopus Agile is currently 5-8 years, depending on your usage profile. With solar, payback drops further.

Compatible with any existing solar

We can add AC coupled storage to systems running:

SolarEdge (with or without optimisers)
SMA Sunny Boy / Tripower
Solis (1G, 3G, 4G, 5G)
Growatt (older and newer models)
Fronius Primo / Symo
GivEnergy AC inverter (existing solar-only setups)
Huawei SUN2000
Fox ESS solar-only inverters
Older systems including Power-One, Eltek, Aurora and decommissioned brands

We'll check compatibility during the site survey — there's almost nothing in the UK domestic market we can't AC couple.

Battery options we install

Battery	Capacity options	Best for
Tesla Powerwall 3	13.5 kWh modular	Larger homes, premium build
SigenStor by SigEnergy	5 / 8 / 12 / 16 kWh	V2H-ready, smart tariff integration
GivEnergy Giv-Bat	5.2 / 9.5 / 13.5 kWh	UK-built, value option
Huawei LUNA	5 / 10 / 15 kWh modular	SolarEdge / Huawei systems
Pylontech	2.4 / 3.5 / 4.8 kWh stackable	Off-grid and small standalone
Fox ESS	5.8 / 11.6 kWh	Budget retrofit

SigenStor — modular & scalable

Stack-and-grow architecture: start with 9 kWh, add modules as your needs change. AC coupled by default, V2H ready, and the same one-app ecosystem for solar, battery and EV. Best fit for households who want flexibility.

SigenStor service page →

Three SigEnergy SigenStor modular batteries side by side — Modular from 9kWh to 54kWh — grows with your needs

Tesla Powerwall 3 product close-up with red switch visible — 13.5 kWh, 11.5 kW continuous output, integrated solar inverter

Tesla Powerwall 3 — premium fixed capacity

Single 13.5 kWh unit with whole-home backup as standard. Industry-leading 11.5 kW continuous output (most rivals max out at 5 kW). Best fit for higher-demand households who want a "set and forget" install.

Powerwall service page →

Costs

Standalone battery

£2,800-£5,500

5-13 kWh installed, no solar

AC coupled add-on

+£200-£600

Above DC retrofit, for additional inverter / cabling

0% VAT

Until March 2027

All home batteries qualify

Smart tariff integration

Where AC coupled storage really earns its keep is on a time-of-use tariff. Most of our installs are configured for Octopus Flux (charges at 2-7p in solar hours and 5-7p overnight, discharges at 24p+) or Intelligent Octopus Go if you also have an EV. See our smart tariff guide for a full breakdown.

The battery management system manages the import/export schedule automatically — you set it once and forget about it.

Free survey and fixed-price quote

We'll check your existing solar system, recommend the right battery for your usage and tariff, and quote you a fixed price.

Get Free Quote

Frequently Asked Questions

Can I add a battery to my existing solar panels?

Yes — that's exactly what AC coupled battery storage is designed for. Your existing solar inverter stays in place; we add a separate battery inverter and battery.

Do I need to replace my solar inverter?

No. AC coupling means your existing inverter is untouched. This is the main reason to choose AC over DC for a retrofit.

What's the difference between AC coupled and DC coupled?

AC coupled has two inverters (solar + battery) — best for retrofits. DC coupled uses one hybrid inverter for both — slightly more efficient but only really suitable when you're installing solar and battery at the same time.

Can I install a battery without solar?

Yes. A grid-charged battery on a smart tariff like Octopus Agile pays back in 5-8 years on its own. When you do add solar later, the battery is already there.

Will the battery work during a power cut?

Only if it's specifically configured for backup. Most retrofit batteries are not by default — we can add backup capability if you want it (typically £400-£800 extra).

How long do home batteries last?

Typically 10-15 years in normal use. Most major brands warranty either 10 years or a specific number of full charge cycles (typically 6,000-10,000).

What's the round-trip efficiency?

AC coupled systems are around 90% — you get 90 kWh back for every 100 kWh stored. DC coupled is slightly higher at around 94%. The retrofit benefit usually outweighs the small efficiency difference.

Do batteries qualify for 0% VAT?

Yes — all home battery storage qualifies for 0% VAT until March 2027, including standalone (no-solar) installs.

Ready to get started?

Free no-obligation quotes from your local MCS & NAPIT certified installer in Milton Keynes and Buckinghamshire.