What we fit

Adding a battery to your existing solar.

Panels fitted five or ten years ago are usually still doing their job — and still exporting most of what they make while the house is empty. Add a battery to that existing solar and it keeps the generation for the evening instead.

It is a different job from a new system: the roof stays as it is, and the work is at the inverter, the board and wherever the battery is going to live.

Get a free quote Try the roof studio
MCS certified
Certificate on the about page
Survey first
Before anything is designed
Based in
Ellesmere Port, Cheshire
A battery cabinet on a brick wall beside its isolator and warning labels
A battery cabinet on a brick wall, isolator and labels beside it

In short

Most existing solar systems can take a battery; whether it sits beside the current inverter or replaces it depends on what is already on your wall. A battery added to panels you already have is zero-rated for VAT until 31 March 2027 when one firm supplies and fits it.

HMRC VAT Notice 708/6 (energy-saving materials)

The roof studio

Turn the house, fill the roof.

A Cheshire semi on a turntable. Drag it round, then tell it about your roof and your house — the panels, the battery, the current running through it and the numbers all move together.

01Your roof

Which way the roof faces
Roof pitch
Shading

02Your house

£120 a month
Home during the day?
Book a survey with these figures

Estimated generation

3,870

kWh a year

Estimated saving

£834

a year, saved and earned

Estimated payback

10.1

years

System size

4.40 kWp

Panels

10

Your use covered

58%

Of what the roof generates

Used in the house70% Exported30%

Worked out for a typical Cheshire roof at the pitch and aspect you picked, on a unit rate of 28p and an export rate of 6.5p — rates this tool assumes, dated September 2026, rather than any tariff you have been offered. Nothing here is a quotation: your roof, your shading and how much electricity you use while the sun is up are what the survey settles.

Take the figures with you.

Copy what the studio worked out for your roof, or send it straight to us with a survey request. None of it is a quote: the survey replaces every figure above with your own.

Book a survey with these figures How we size a system
Every assumption behind the numbers
Unit rate
28p for every unit (kWh) you’d otherwise buy from the grid.
Export rate
6.5p for every unit the house and battery can’t use and send back to the grid.
Your yearly use
Worked out from your monthly bill at the 28p unit rate, after a standing charge of about 36p a day — and never less than 1,100 kWh a year.
What a panel makes
Each panel is 440 W (0.44 kWp). A kWp makes 880 kWh a year facing south, 760 facing east–west and 620 facing north-ish. For this part of Cheshire the EU’s PVGIS model gives 951 for a south roof at a typical pitch — the studio stays below it.
Pitch
Shallow (28°) makes 95% of a typical 38° roof; steep (48°) makes 97%.
Shading
A bit of shade costs 10%; heavy shade costs 24%.
How many panels
Two rows, growing with your bill from three columns to eight — six panels up to sixteen.
How much you use yourself
The share of what the roof makes that the house uses: 30% if you’re usually out, 46% in and out, 62% usually home. A battery adds 24 points and a car charger 6, up to 86% — and never more than 62% of your whole year’s use.
Saving
The units you use yourself at 28p, plus the units you export at 6.5p.
Payback
The yearly saving set against what a system like the one you’ve built typically costs to install: a base figure, an amount for each panel, and more again for a battery or a charger. The answer is held between 4 and 25 years. The studio never shows that cost, because only a survey can price your roof — so treat the years as a rough guide, not a figure to hold us to.

Monthly and yearly sunshine for this area: PVGIS 5.2, EU Joint Research Centre. The unit rate, the export rate and the standing charge are the studio’s own assumptions, set in September 2026 — not a tariff we have quoted you. Your own rates are on your bill, and a survey works from those.

Retrofit battery

Two ways to add storage to an existing array.

The first is AC-coupled: the battery has its own inverter and sits alongside what you already have. Nothing on the roof is touched, the original inverter keeps working, and the battery charges from the surplus at the board.

The second is a hybrid replacement: your existing inverter comes out and one that handles both panels and battery goes in. It is neater and often more efficient, but it means changing the part of the system that is currently working.

An inverter and two battery units on a brick wall beside a drive, isolators on white trunking between them
An inverter and its isolators on an outside wall

Retrofit battery

What we check on an existing system.

  • What is actually fittedInverter make and model, array size, and what the original installer left behind in the way of certificates and isolation.
  • How much it exportsYour half-hourly data, or a clamp on the meter tails for a week, tells us what there is to store — and stops us selling you capacity that will sit empty.
  • The boardWhether there is a way in for another supply, and whether anything at the board needs bringing up to date first.
  • The paperwork trailIf the original system has an MCS certificate and an export arrangement, we keep both intact; adding storage should not cost you either.
  • Somewhere to put itSame rules as any battery: temperature, clearances and access, settled at the survey.
Black panels on the tiled roof of a house with a first-floor balcony
Panels on a tiled roof, with a first-floor balcony below

Retrofit battery

What changes, and what does not.

The roof
Untouched in an AC-coupled retrofit. No scaffold, no panels moved.
The export
You export less, because you use more of your own generation. Any export arrangement you hold continues.
The network
Adding storage is notified to the network operator in the same way a new system is.

Retrofit battery

Done in a day, in most houses.

A straightforward AC-coupled retrofit is a day’s work: mount the battery, run the cable, wire in at the board, commission and label. A hybrid swap takes longer because the array comes off the old inverter and on to the new one.

Either way, you finish with one app that shows generation, storage and use together, set up with you before we leave.

Battery cabinets on an outside brick wall, isolators and a distribution box on one run of white trunking
Battery cabinets on an outside brick wall, cabled through white trunking

Retrofit battery

How a retrofit runs.

  1. 01Photos firstPictures of the inverter, the board and the meter answer half the questions before anyone travels.
  2. 02SurveyThe rest on site: siting, cable route, and what the existing kit will play with.
  3. 03DesignAC-coupled or hybrid, what size, and what it will and will not do in a power cut.
  4. 04Install and hand overFit, commission, notify the network, and set the charging windows up with you.

What we fit on these jobs

The kit, and the rest of the work.

From the Google profile

Homeowners on this work.

3 of our 39 Google reviews are about a battery retrofit. Here they all are, word for word.

The Google profileSee them on Google →

Electrifyd saved the day. We wanted a battery upgrade to an existing system with some installation challenges and they weren't phased at all. No moaning about difficulty and no excuses. Just a straightforward plan and within a couple of weeks we were sorted. This is exactly what we needed after trying other companies and not getting very far.

Really neat installation and unmatched comms, I'd recommend them to anyone.

Gareth TerraceGoogle review · November 2025

TLDR - Excellent team who provided 5 service throughout at a great price with excellent technical knowledge to deliver a 17.28kW peak solar panel system with 67.5kWh Tesla battery storage

Excellent team at Electrifyd; Andre and Daniel ensured that my solar project was delivered at a great price with support all the way through the planning; installation and after care.

I had a complex installation planned with all 4 roof surfaces to have panels installed and a multiple powerwall 3 set up that needed to work with an existing solar system installed on my garage and eddi solar hot water diverter.

Andre ensured the G99 application was completed quickly and kept me updated on the progress which resulted in approval for 22kW inverter acceptance and a 15kW export limit.

Andre worked with me to provide the highest output of panels that would fit on the roof and meet MCS requirements not just supplying a default panel but looking at the best way to design the system.

The installation went smoothly, Andre and Daniel consulted with me throughout to deliver a neat and minimally intrusive installation. Ensuring all cables were hidden where possible and confirming their route before committing to installation.

Commissioning the system went well and Andre ensured I knew how the Tesla app worked and demonstrated how the system would respond to a grid failure.

The system has performed well so far and has generated 5,653kWh in just under 3 months making my electricity bill negative with SEG export and arbitrage through importing off peak electricity and exporting at peak times.

Andre ensured my Eddi system worked well with the new setup and installed a wireless CT clamp to allow both my existing system and the tesla system to heat the hot water as needed.

After care communication has been good and Andre has answered all questions quickly.

I have recommended Electrifyd to work colleagues because I was happy with the work provided and I would use the team again for future projects.

Read it in full on Google
Daniel HaighGoogle review · June 2026

Following the initial installation of a full system - PV panels, Inverter, EV charger and Battery - Electrifyd have added two additional battery modules to increase capacity! Again, a prompt, professional service, a satisfied customer and a first class solar system!

Jim BlackGoogle review · September 2025

All the reviews, with the replies

Asked on every survey

Retrofit battery, the questions first.

If yours isn’t here, give us a ring and ask, or see every question.

Yes. Adding a retrofit battery to your existing solar system is a smart and cost-effective way to get more out of your investment. We install retrofit batteries to boost solar efficiency, cut energy bills, and provide backup power.

All our FAQs

From the blog

Worth reading before you decide.

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Where we do it

Adding a battery to existing solar, town by town.

From our base in Ellesmere Port, across Cheshire, Merseyside and Greater Manchester. The towns nearest us come first.

Cheshire

The kit we fit in Cheshire: Tesla Powerwall installer, Cheshire · Fox ESS installer, Cheshire · EcoFlow installer, Cheshire.

Merseyside and the Wirral

The kit we fit in Merseyside & Wirral: Tesla Powerwall installer, Merseyside & Wirral · Fox ESS installer, Merseyside & Wirral · EcoFlow installer, Merseyside & Wirral.

Greater Manchester

The kit we fit in Greater Manchester: Tesla Powerwall installer, Greater Manchester · Fox ESS installer, Greater Manchester · EcoFlow installer, Greater Manchester.

Before the survey: Adding a battery to the solar you already have · Fox ESS batteries, explained.

Add a battery to existing solar anywhere on the map: the survey starts with the inverter you already have.

Start here

Start with a conversation, not a quote.

Tell us the postcode and roughly what you use. We’ll tell you honestly whether the roof is worth doing — and if it isn’t, that’s a perfectly good answer too.

Tell us about your roof

What are you after?

Or call 0330 133 6441

Thanks — we have it.

It’s with us now, and we aim to reply within a couple of hours.

  • Takes about a minute
  • You get a person, not a brochure
  • No obligation, and no visit until you ask for one