Why your tariff moves payback more than your kit does

Same system, three tariffs, seven years of difference

Take one system and hold everything about it constant. A 10 panel 4.5 kWp installation with a 5.2 kWh battery, £9,644 from the OVO regional partner pricing matrix, generating 4,492 kWh a year at the UK average of 998 kWh per kWp. The home uses 3,500 kWh of electricity a year, keeps 1,800 kWh of what the roof makes and sends 2,692 kWh to the grid. Every unit imported costs 26.11p, the Ofgem average capped electricity unit rate for 1 July to 30 September 2026. None of that changes in the table below. The panels are the same panels, the battery is the same battery, the roof faces the same way, and the only variable is what somebody pays you for the exported units.

Worked on the system described above at £9,644 installed, 1,800 kWh self consumed and 2,692 kWh exported, with imports valued at the Ofgem average capped unit rate of 26.11p per kWh for 1 July to 30 September 2026. Simple payback, with no rate inflation and no discounting. The 20p rate is OVO SEG Install Exclusive, which requires OVO to have installed both the solar and the battery, that you take your electricity supply from OVO, and a system under 30kW. Solar only on the same tariff pays 15p. Rates correct at July 2026 and subject to change.

That is a £430 a year spread and just over seven years of payback, produced entirely by a decision made before anyone climbed a ladder. There is no extra hardware in it and no better roof, only the same units leaving the house at four different prices.

What the same money buys in kit

Put that £430 a year next to what you would have to spend on hardware to earn it. Installed cost on our pricing matrix runs at roughly £439 per extra kWp once the fixed costs are paid, and each extra kWp yields around 998 kWh a year. To generate £430 of value at a 20p export rate you need about 2.15 kWp more, which is roughly five more panels and about £944 of spend. That is a perfectly good use of £944, and on most roofs it is the right call, but it is £944 set against a tariff decision that costs nothing extra and delivers the same result. Unlike panels, the tariff is not limited by how much roof you have or by what your network operator will let you connect.

• Kit choice decides how much you generate. Panel wattage matters most when roof space is the binding constraint rather than budget. If the roof has room, size beats specification, which filling the roof first time works through.
• Kit choice decides how well you cope with shade. This is the one place hardware genuinely rescues a difficult roof. Optimisers, microinverters and string inverters sets out which applies where.
• Kit choice decides what you still have in year 12. Retained capacity terms differ meaningfully between battery manufacturers, and battery warranties explained covers what to read.
• Tariff choice decides what all of that is worth. It multiplies every kWh the system will ever produce, and it is settled by who installs the system and who supplies your electricity.

Which band your export rate sits in

Headline rates look wildly inconsistent until you sort them by what they are conditioned on: 3p to 6p open to anyone, 12p to 15p where you have to buy your electricity from the same supplier, 17.5p to 25p where that supplier installed or sold you the system as well, and a separate time of use option for battery homes that pays its best rate for a narrow late afternoon window. The full band table, with the named tariffs and the date each rate was checked, sits on the 20p export rate explained.

The time of use option is the one people miss. It pays a peak rate for a few hours a day, which only works if you have a battery holding charge until that window opens. That is a strategy question rather than a rate question, and our solar and battery strategy page goes through how the two interact.

The import side moves too, and it moves every quarter

Half of the return in that first table came from imports you no longer buy, so the price cap sits underneath every payback figure anyone quotes you. The cap for 1 July to 30 September 2026 rose 13% on the previous quarter, announced on 27 May 2026, driven mainly by wholesale gas. Average capped rates for the quarter are 26.11p per kWh for electricity and 57.19p a day standing charge, with regional and payment method variation on top. Ofgem also restated the typical annual bill from £1,862 to £1,663 without changing a single unit rate. It cut the assumed consumption of a typical household to 2,500 kWh of electricity and 9,500 kWh of gas, because homes now use 7% less electricity and 17% less gas than the October 2023 benchmark. Same cap, different arithmetic underneath the headline. It is a useful reminder to check what a quoted saving is measured against.

How to check a headline rate before you believe it

1. Find the condition. Every rate above about 12p is gated on your supply, your installer or both. If the condition is not stated on the page, it exists anyway.
2. Check the term. Some of the top rates are fixed for 12 months and then fall a long way. A 20p rate that becomes 4.5p in year two is not a 20p rate.
3. Check the system size limit. The bands vary from 15kW to 30kW to 5MW depending on the supplier, and it is the number that quietly rules people out.
4. Check whether you need to switch import supplier, and price that switch. A better export rate on a worse import tariff can leave you behind.
5. Check the date the rate was published. Export tariffs move often, and a comparison article from six months ago is describing a market that has already changed.
6. Do the arithmetic on your own export volume, not a national average. At 2,692 kWh a year each penny is worth £27. At half that volume it is worth half as much.

Where that leaves your decision

Choose the kit for the roof you have, then choose the tariff that pays the most for what that roof produces, and understand that the second decision is usually worth more than any refinement of the first. Our solar panel costs page sets out what the hardware runs to, the Smart Export Guarantee page carries the eligibility detail in full, and why the best export rates have conditions explains what suppliers are buying when they pay above the market. When you want it costed on your own roof, the coverage map finds the local OVO expert for your area.