With solar and a Powerwall but no EV, Octopus Flux came out on top in our numbers, as long as the battery sells spare charge at the evening peak. Add an EV and Intelligent Octopus Go takes over.
Solar + Powerwall: Octopus Flux, −£101 a year (Octopus pays you).
Solar + Powerwall + EV: Intelligent Octopus Go, −£16 a year with peak selling, or £295 without.
For comparison, the same solar and battery home on Flexible pays £339.
Battery allowed to sell spare charge at the evening peak. South East, yearly electricity cost.
| Tariff | Paired with | A year |
|---|---|---|
| Octopus Flux | Flux export | −£101 |
| Intelligent Flux | Intelligent Flux export | −£4 |
| Agile Octopus | Agile Outgoing | £132 |
| Flexible Octopus | Outgoing (12p) | £339 |
Flux charges the battery cheaply between 2am and 5am (14.8p), runs the house from solar in the day, then pays about 29.8p for every unit you sell between 4pm and 7pm. If you'd rather keep the battery for the house, the order changes: Intelligent Flux £177, Flux £209, Agile £231.
| Tariff | Paired with | A year |
|---|---|---|
| Intelligent Octopus Go | Agile Outgoing | −£16 |
| Octopus Go | Agile Outgoing | £100 |
| Octopus Flux | Flux export | £236 |
| Agile Octopus | Agile Outgoing | £420 |
| Intelligent Flux | Intelligent Flux export | £461 |
| Flexible Octopus | Agile Outgoing | £843 |
Intelligent Go's 6.6p night rate does the heavy lifting: the car and the Powerwall both fill up overnight, and the battery covers the house through the 29.0p day rate.
| Region | Solar + battery | A year | Solar + battery + EV | A year |
|---|---|---|---|---|
| East England | Octopus Flux | −£97 | Intelligent Octopus Go | −£14 |
| East Midlands | Octopus Flux | −£86 | Intelligent Octopus Go | £19 |
| London | Octopus Flux | −£108 | Intelligent Octopus Go | −£29 |
| Merseyside & North Wales | Octopus Flux | −£51 | Intelligent Octopus Go | £53 |
| West Midlands | Octopus Flux | −£62 | Intelligent Octopus Go | £35 |
| North East | Octopus Flux | −£45 | Intelligent Octopus Go | £82 |
| North West | Octopus Flux | −£130 | Intelligent Octopus Go | −£15 |
| Southern | Octopus Flux | −£102 | Intelligent Octopus Go | −£18 |
| South East | Octopus Flux | −£101 | Intelligent Octopus Go | −£16 |
| South Wales | Octopus Flux | −£91 | Intelligent Octopus Go | £46 |
| South West | Octopus Flux | −£80 | Intelligent Octopus Go | £18 |
| Yorkshire | Octopus Flux | −£29 | Intelligent Octopus Go | £61 |
| South Scotland | Octopus Flux | −£9 | Intelligent Octopus Go | £95 |
| North Scotland | Octopus Flux | −£63 | Intelligent Octopus Go | £48 |
Whichever tariff you pick, put its prices into the Tesla app's time-based settings so the Powerwall knows when power is cheap and when it's dear. Allow grid charging if you want it to fill up overnight, and choose whether it may export everything or solar only. Tools like Predbat in Home Assistant can plan this day by day.
Intelligent Flux only works with batteries Octopus can control directly. Check Octopus's current list of compatible batteries before choosing it. Plain Flux works with any battery, as long as you set the battery's timings yourself.
On Flux, selling at the 4–7pm peak (about 29.8p in the South East) is where most of the value comes from. In our numbers it turned a solar and battery home from £209 to −£101 a year on Flux.
Then Intelligent Octopus Go usually wins. In the South East a home with solar, a 13.5 kWh battery and an EV came out at £295 a year on Intelligent Go without selling battery power back, or −£16 with it.
Usually not the winner, but it widens the gap: a bigger battery can carry more cheap night power into the evening and has more to sell at the peak. Try 27 kWh in the Tariff Finder.
We run a typical home through a year, half hour by half hour, on each tariff using Octopus's published prices for the region. The example home uses 3,100 kWh a year before any EV or heat pump; the EV does 8,000 miles at 3.5 miles per kWh and charges in the cheapest slots; solar is 4 kWp (about 3,600 kWh a year); the battery holds 13.5 kWh and charges or discharges at up to 5 kW. Agile uses the average price for each half hour of each month from October 2025 to September 2026, so a cold, still winter can cost more. Each tariff is paired with whichever export tariff pays more. Figures are electricity only, including the standing charge, and negative numbers mean Octopus pays you.
Run your own numbersPick your region, tick what you have, or upload your Octopus usage file. Free, no sign-up.
Open the Tariff Finder →