Solar & Battery
Solar PV and battery storage to generate, store and control your own energy
Your roof earning all day, your battery spending it all evening — with 0% VAT on the install and the Smart Export Guarantee paying for whatever is left over.
See How It Works
Two drawings. How the system works, and what it does to your money.
*Illustrative guide figures while launch pricing is finalised — your exact numbers follow the free survey.
What We Do
Solar panels let you generate clean electricity from your own roof, and a home battery lets you store it for the evening instead of exporting it cheaply to the grid. OKPW designs and installs MCS-certified solar PV and battery systems sized to your actual usage, with a clear, honest projection of savings and payback — not inflated promises. We handle the structural assessment, the DNO and G99 applications, the install and the monitoring set-up, and because we're a design & build company we can integrate everything cleanly with a heat pump, EV charger or a wider renovation.
What It Is For — and What It Is Not
Solar generates electricity on your roof. A battery does not generate anything — it moves when you use what you generated. Understanding that difference is most of what decides whether a battery is worth buying.
Right for your house if…
- You have an unshaded roof with a decent orientation. A 4 kWp array on an unshaded south-facing London roof at about 30° generates roughly 3,400–3,900 kWh a year; east, west, shaded or shallow generates materially less.
- Somebody is home during the day, or you will genuinely shift washing, dishwashing and car charging into daylight.
- You are staying put. This is a decade-scale proposition.
- The roof covering has plenty of life left. Stripping panels to re-roof later is money spent twice.
- You want a battery for a time-of-use tariff, not just to store your own sunshine — that is where the numbers actually work.
Not what you want if…
- You expect it to run the house off-grid. It cannot: anti-islanding means the system shuts down in a power cut unless backup is specifically specified and wired, which is not included by default.
- You are buying a battery purely to store your own generation on a flat single-rate tariff. On current figures it does not repay its cost inside its warranty.
- The roof is near the end of its life, or visibly shaded. A quote showing no shade factor on a shaded roof is not compliant with the standard it claims to work to.
- You are out all day, use little electricity, and will not change when you use it.
- You are moving within about five years. We make no claim that solar returns its cost in the sale price.
- You are a leaseholder without written freeholder consent. Planning rights are a planning matter; most London leases separately prohibit alterations to the roof.
- The building is listed. That is a separate consent regime and unauthorised work is a criminal offence.
There is no general domestic solar grant in England. The Boiler Upgrade Scheme is heat pumps and biomass only. 'Solar grants available' is one of the most common misleading claims in this market, and you should treat anyone making it with caution.
Key Benefits
- Generate your own electricity and cut reliance on the grid
- Store daytime solar to use during the evening peak
- Honest, usage-based payback figures — no inflated promises
- MCS-certified, with all DNO paperwork handled for you
Our Process
Survey & Roof Check
We assess roof orientation, pitch, shading and structure, and review your electricity bills to size the system around how you actually use power.
System Design
A bespoke MCS design for panels, inverter and battery, with a transparent generation, self-consumption and payback estimate.
Applications
We handle DNO / G99 notification and all paperwork so your system is fully compliant and eligible to export.
Installation
Scaffold, mounting, panels, inverter and battery installed safely and tidily by our qualified team, typically in one to two days.
Commissioning & Monitoring
The system is tested, registered, and connected to a monitoring app so you can see generation, storage and savings in real time.
What's Included
- Roof & structural assessment
- Bill analysis & system sizing
- MCS-certified solar PV panels
- Hybrid inverter
- Home battery storage
- Bird & pest protection
- Scaffold & safe access
- DNO / G99 application
- MCS certificate & MCS handover pack
- Real-time monitoring app set-up
- Smart Export Guarantee guidance
What You Need to Know Before You Buy
The numbers that decide it, including the ones most quotes leave out.
You will use about a quarter of it, not half
Without a battery, the industry's own modelling puts self-consumption at about 24% for a typical household. The widely quoted 50% is not a measurement — it came from the old Feed-in Tariff, which deemed export at half of generation for administrative convenience. Any quote built on 50% is overstating your saving by a wide margin.
What a battery actually buys
Self-consumption goes to roughly 60–64% at 4–6 kWh of storage and about 73% at 10–11 kWh, then flattens. The first 5 kWh buys around 36 percentage points; the second only about 13. Bigger is not proportionally better.
The battery payback, bluntly
Shifting that extra generation is worth roughly £150–£260 a year depending on your export rate. A £4,000–£5,000 battery therefore takes something like 16 to 30 years to repay, against a 10–12 year warranty — before round-trip losses and capacity fade. It earns its keep on a time-of-use tariff, or where an export tariff requires one. Not on its own.
What export actually pays
Exported units earn far less than imported ones cost. Across the last full reporting year the average actually paid was 15.4p per kWh on tariffs tied to your import supplier and 7.3p untied, against an import cap of 26.11p. Average annual export earnings were £151 tied and £119 untied. There is no floor — rates as low as 1p have been offered — and it is not the Feed-in Tariff.
Payback on the whole system
Roughly 12 to 18 years on current figures. About £7,100 installed for 4 kW; roughly £450–£670 a year in saved imports plus export income, before you replace the inverter. Adding a battery on a flat tariff lengthens it. Challenge any quoted payback under eight years.
A structural check is mandatory, and London roofs often need an engineer
The standard requires the roof structure to be checked by a competent person, and names traditional cut roofs with hips or valleys — most of London's Victorian stock — as needing a structural engineer. Since June 2026 documented evidence of the assessment and a wind-load calculation for the specific mounting system is required. Budget for the engineer.
Your roof warranty needs written agreement
The standard requires the warranty provider to be consulted, notified in writing and to give explicit written agreement. A clause in the installer's own terms does not satisfy it. Ask to see the correspondence.
Planning, and what changes on 27 August 2026
Panels are normally permitted development within limits — no more than 0.2m beyond the roof slope and not above the ridge. A front roof slope in a conservation area is permitted, because the restriction bites on walls rather than roofs. A flat roof on article 2(3) land — much of inner London — needs prior approval first. A statutory instrument in force on 27 August 2026 rewrites these rules, so we work from the instrument itself rather than a summary page.
The inverter and battery are consumables
Both will need replacing within the life of the panels. Ask any installer to show you their payback figures with those replacement costs included, using the warranty terms of the specific products they are quoting.
VAT is 0% until 31 March 2027
Then 5%. About £600 on a £12,000 job. It applies UK-wide, and it covers batteries too — including a battery retrofitted to existing panels, or one storing grid electricity on its own. Many people still believe a battery only qualifies if fitted at the same time as the panels. It does not.
Figures correct at 10 August 2026, from Ofgem's Smart Export Guarantee annual report, MCS guidance, DESNZ solar cost statistics and HMRC. Prices are market guides, not a quote.
Why Choose OKPW
Generate & Store
Panels plus battery means you use your own power in the evening instead of buying it back at peak rates.
Honest Payback
Clear, realistic savings and payback figures based on your real usage — no inflated sales numbers.
Integrated Energy
Pair solar with a heat pump and EV charger for one coordinated, future-proof home energy system.
Common Questions
How many panels do I need?
We size the system from your actual electricity bills and roof space, so you’re not over- or under-sold.
Is a battery worth it?
For most homes, yes — it lets you use more of your own solar instead of exporting it cheaply. We’ll show you the numbers for your usage.
Can I add it to a heat pump or EV charger?
Yes — we integrate solar, battery, heat pump and EV charging into one coordinated system.
Make Your Home Worth More
A free, no-obligation survey by the people who do the work — covering Putney, Wandsworth, Richmond, Kingston, Streatham and Lewisham.
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