Home → The strategy
The strategyCharge off-peak. Fill the roof. Sell the rest at 20p.
The order you do things in changes what solar pays back. Here is the sequence we design to, and the maths behind it.
Size the battery to your day, not your roof
A battery isn't a solar accessory. It's a tariff arbitrage machine that happens to pair well with panels.
A typical UK home uses 8 to 12 kWh of electricity a day, and a large chunk of that lands in the 4 to 9pm peak, exactly when electricity is most expensive. Fill a battery overnight at the off-peak rate, run the house off it through the evening, and you're buying the same electricity at roughly half price.
Crucially, this works in January. It doesn't wait for the sun. That's why it comes first, it's the part of the system with no weather risk attached.
Oversizing wastes money: a battery you only half-cycle earns half as much. Match it to what you actually get through in an evening.
A typical day, on the right tariff
Illustrative. Off-peak windows vary by tariff, OVO's Off-Peak plans typically run overnight plus an afternoon window.
We size the battery around your evenings, not your roof.
Fill the roof. All of it.
Scaffolding, labour, the inverter, the DNO application and certification cost the same whether you fit 6 panels or 14. Only the panels scale.
Cost per kWp falls off a cliff as the system grows
+25% on the price. +133% on the generation. Bar length shows cost per kWp; the label shows total installed price.
Fixed, whatever the size
Scaffolding, labour (£2,051 flat), inverter, DNO paperwork, MCS certification. You pay it on 6 panels or 20.
Per extra kWp
The marginal cost of capacity. Cheap, which is exactly why you should buy as much of it as your roof allows.
Paid for every surplus unit
You don't need to consume it. At 20p per kWh export, extra generation is income rather than waste.
45 minutes on video. See your own roof laid out panel by panel.
Sell what you don't use, and be smart about what "using it" means
This is the part that decides whether a battery pays for itself.
Two ways to fill the same battery
Both give you a full battery for the evening peak. They are not worth the same amount.
Charge the battery from your solar
benefit per kWh
- Import you avoid+26.11p
- Export income given up-20.00p
- Net+6.11p
Charge the battery off-peak, export the solar
benefit per kWh
- Import you avoid+26.11p
- Off-peak unit you buy-13.00p
- Net+13.11p
Plus your solar still earns the full 20p on the way out.
The reason it works: a 20p export rate is high enough that exporting is nearly as good as self-consuming. So the battery's job stops being "store sunshine" and becomes "buy cheap electricity". Your solar goes out to the grid at full price instead.
Assumes 26.11p import, ~13p off-peak, 20p SEG Install Exclusive. Off-peak rate depends on your tariff, confirm your own before relying on it. Our design tool models both strategies for your home and configures whichever pays more.
What it adds up to
A 14-panel system with a 5.2 kWh battery, on a typical home using around 3,500 kWh a year.
Where the money comes from, each year
- Total benefit, year one≈ £1,531
- System price installed£10,434
- Payback≈ 7 years
Payback by system size
Panels are warranted to keep performing for 25 years. A 7-year payback means roughly 18 years of pure return.
Instant prices are a thing of the present
You should not need a salesperson in your front room to find out what solar costs. Answer a few questions and see a real number for your home.
If it looks right, this is the whole process from there:
- We consult and design, on videoYour roof on screen, sized around how you actually use energy. About 45 minutes.
- You get a quote in writingA fixed price from your local expert, on the call, not posted out next week.
- Letter of authority and grid applicationYou sign an LOA so we can handle the grid application for you, and a deposit holds your install slot.
- Technical survey, then installYour local team confirms everything agreed remotely, then fits it. Usually one to two days.
Want your own numbers, on your own roof? A free 45 minute remote design gives you the layout, the generation forecast and a written price, with no home visit.
Get your free quote →Solar & battery installers in Bristol
Yes, show me →Why being the supplier and the installer matters
A standalone installer can't offer you an export rate. They don't own a tariff. OVO does, which is the whole reason these numbers work.
| Rate | p / kWh | Who gets it |
|---|---|---|
| SEG Install Exclusive, solar + battery | 20p | OVO installs both your solar and your battery |
| SEG Install Exclusive, solar only | 15p | OVO installs your solar, battery elsewhere or none |
| SEG Beyond Exclusive | 12p | OVO energy customers |
| SEG Standard | 4p | Open to customers of any supplier |
| Import, Standard Variable | 26.11p | What you pay at peak |
| Import, off-peak (illustrative) | ~13p | Depends on your tariff and time window |
Rates correct at July 2026 and subject to change. Standing charge 57.19p per day. Confirm current rates before purchase.
What actually goes on your wall
Your local OVO expert fits the EcoFlow OCEAN 2. Here is what it looks like, and why its shape suits the way we size systems.
It stacks, so it fits your usage
The OCEAN 2 is built from 5 kWh packs that stack on top of each other. That matters because of the point we made further up this page: the right battery is the one that covers your evening and overnight use, not the one with the biggest number on the box. Stacking lets your expert size it to your actual day.
If your usage changes later, a bigger EV, a heat pump, someone working from home, the stack takes more packs. One inverter carries up to twelve of them.
It keeps the house on in a power cut
Whole-home backup is built in rather than being an extra box on the wall, and it switches over in 0 ms, which is fast enough that your lights do not flicker. Most batteries need separate hardware to do this at all.
Indoors or outdoors, floor or wall
It is IP66 rated and can be floor or wall mounted, so it does not have to live in the one spot your garage happens to allow.
Single phase or three phase, both covered
Most UK homes are single phase and there is a single phase inverter for exactly that. If your property is three phase, there is a three phase version, and your expert will tell you which one you have on the design call rather than leaving you to work it out.
The inverter handles the solar and the battery together, so there is one unit doing both jobs rather than two boxes and two things to go wrong.
OCEAN 2 specifications from EcoFlow's OCEAN 2 three-phase product brochure, March 2026: 5 kWh battery packs, up to 12 packs per inverter, 10,000+ battery cell cycles, 0 ms switchover with 63A whole-home backup, IP66 rating, up to 97.8% maximum efficiency. Warranty terms as quoted by EcoFlow. Capacity fitted depends on your usage and your property, and is confirmed on your design call.
Go deeper before your design call
Straight answers from the OVO Solar and Battery team, sourced and dated.
AC versus DC coupled batteries, explained simply
One suits a retrofit, one suits a fresh install. The plain English difference.
Read the guide →Adding a battery to solar you already have
Your panels stay untouched. The grid application is the part that catches people out.
Read the guide →What a gateway does, and when whole home backup is worth it
A full battery is no use in a power cut without a gateway. Here is what one does.
Read the guide →How to read a battery warranty before you sign anything
Four numbers, the conditions underneath them, and a five minute way to compare two quotes.
Read the guide →A home battery without solar panels, honestly assessed
A battery with no panels still earns every night. Here is how much, and where it does not stack up.
Read the guide →How much a home battery saves, unit by unit
What a battery saves per unit, per night and per year, with the losses taken off.
Read the guide →Get your free quote
Takes about two minutes. Your local OVO expert confirms your free video design within one working day.
Have it designed properly
A local OVO expert will model this for your roof, your usage and your tariff on a free 45-minute video call. No home visit. No obligation.