Solar battery and tariff terms, explained
The words you meet when you own a home battery or solar panels in the UK, each explained in a few lines, with real figures where we have them and a link to the guide that goes further.
What you pay, and when.
A battery earns its keep from the difference between prices, so the tariff decides most of what it can save.
Five Octopus tariffs over a yearWhat is a time of use tariff?
A tariff whose price depends on the time of day. Some have two or three fixed bands, such as a cheap night; others change every half hour. They need a smart meter, which records your use each half hour, and they are where a battery saves most.
What is Octopus Agile?
An Octopus import tariff whose price changes every half hour, following the wholesale market. The next day’s prices are published between 4pm and 8pm. In North West England from October 2025 to September 2026 they ran from −11.7p to 90.6p a kWh: below zero, Octopus pays you to use power. Is Agile worth it with a battery?
What is Octopus Go?
An Octopus tariff with a cheap rate for five hours each night, 00:30 to 05:30, and a single rate the rest of the day. Made for electric cars, and used by battery owners to fill up overnight.
What is Intelligent Octopus Go?
A version of Go for electric car owners, in which Octopus schedules the car’s charging and gives a cheap rate overnight and for the extra hours it chooses.
What is Octopus Flux?
An Octopus tariff for homes with solar panels and a battery, in which both import and export have three bands: cheapest from 2am to 5am, dearest from 4pm to 7pm, and a day rate between. Export pays most in the evening peak, so a battery that holds charge for those hours is paid for it. How Flux compared over a year.
What is Intelligent Octopus Flux?
A version of Flux in which Octopus charges and empties a compatible battery for you. On 13 October 2026 Octopus’s page said it was temporarily unavailable. The ways to schedule a battery, compared.
What is the energy price cap?
The most a supplier may charge per kWh and per day on a standard variable tariff, set by Ofgem every three months. From 1 October 2026 the average single rate by Direct Debit was 26.32p a kWh. It is a cap on the rate, not on the bill.
What is a standing charge?
A fixed amount a day for being connected, paid whatever you use. A battery can’t reduce it. On Octopus’s tariffs in 2026 it was about 43p to 50p a day.
Being paid for what you send out.
With solar panels and no battery, simply being paid for export was worth £408 a year to the typical home in our year of 20 homes.
Store solar or export it?What is the Smart Export Guarantee (SEG)?
The rule that larger suppliers must offer an export tariff that pays more than zero to homes with small generation such as solar panels, fitted by an MCS certified installer. Each supplier sets its own rate and terms. Whether they pay for power a battery charged from the grid and then exported is up to each supplier.
What is Outgoing Octopus?
Octopus’s fixed export rate: the same price for every kWh at any hour. It paid 15p to February 2026 and 12p from March. Against Agile Outgoing on one real home.
What is Agile Outgoing?
Octopus’s export tariff whose price changes every half hour, like Agile for import. It pays least in the middle of the day, when most solar homes export, and most in the evening: in autumn 2026 about 10p between 10am and 3pm against 24p in each day’s best three hours.
What is an export MPAN?
The reference number for the meter point your exports are counted on, separate from the one for import. A supplier needs it before it can pay you for export; if you don’t have one, your supplier can apply for it.
What is an export limit?
The most power your home may send to the grid at once, set when your system was connected. Your inverter enforces it, whatever the sun and the battery could give. What it is, and what it cost one home.
What are G98 and G99?
The rules for connecting generation to the grid. Under G98 a home may export up to 3.68 kW (16 amps on one phase) by telling the network operator; anything bigger needs its approval first under G99, which often sets a limit.
How it is sized, and what it loses.
The numbers on a battery’s datasheet, and what they mean for what it can save.
Is a solar battery worth it?What is the difference between kW and kWh?
A kWh is an amount of energy: what a battery holds, or what you use in a day. A kW is a rate: how fast a battery can charge or empty, or how much a kettle draws. A 10 kWh battery that charges at 5 kW fills from empty in about two hours.
What is round trip efficiency?
The share of what goes into a battery that comes back out, the rest lost as heat in the battery and inverter. On the real home in our guides about a tenth is lost, so a kWh stored is worth a little less than a kWh bought.
What is a battery’s reserve?
The charge a battery keeps back and won’t empty below, often 10% or 20%, to protect its life and to cover a power cut if it supports one. What it can actually use is its size less the reserve.
What is a hybrid inverter?
One inverter for both the solar panels and the battery, so sun can charge the battery without being converted twice. A battery added to existing panels often comes with its own inverter instead, called AC coupled.
What does kWp mean on solar panels?
Kilowatts peak: what the panels produce in full sun under test conditions. In our year a 4 kWp roof facing south made 4,954 kWh, from 147 kWh in December to 712 kWh in July. The sun and the saving, month by month.
Is there VAT on a home battery?
Not until 31 March 2027. Batteries installed in homes are zero rated, whether fitted with panels, added to panels you have, or on their own. From 1 April 2027 the reduced rate of 5% applies.
What a battery is told to do.
The same battery saved the typical home £171 a year in self use and £431 planned every half hour, on the same tariff.
The ways to schedule a batteryWhat is self use (self consumption) mode?
A battery’s default: it stores sun the house doesn’t need at that moment and empties into the house when the sun can’t cover it. It never fills from the grid when power is cheap, and never holds charge for a dearer hour.
What is smart battery scheduling?
Deciding ahead, for each part of the day, when a battery should charge from the grid, hold its charge, power the house or sell, from the tariff’s prices, the solar forecast and how the home uses power. Orza does this every half hour, through the battery maker’s own cloud.
What is battery arbitrage?
Buying power when it is cheap and using or selling it when it is dear. On Agile with Agile Outgoing in autumn 2026, selling in each evening’s best hours and refilling at night cleared about 7p a kWh, after what the battery loses, on 21 of 35 days.
What is clipping, or curtailment?
Sun that is thrown away because the battery is full and the house and the export limit can’t take any more. The inverter turns the panels down, and that sun is lost.
What are Octopus Saving Sessions?
Events in which Octopus pays its customers for using less than usual at a set time, when the grid is under strain. A battery can cover the house through them.
What is Orza?
Orza is free smart scheduling software for home batteries in the UK. It plans your battery every half hour around your tariff’s prices, your solar forecast and how your home uses power, through your battery maker’s own cloud, so there is nothing to install. Free during the beta.
Every half hour of your battery, explained as it happens.
Free during the beta. Connect in a few minutes, and start in Monitor only.