Octopus Energy Fixed vs Flexible EV Tariff: Which Wins?

These are the two flagship overnight EV tariffs. They differ in three places: the cheap-rate window length, the rate itself, and the smart-charger requirement.

On 10,000 miles per year (roughly 2,700 kWh at 27 kWh per 100 miles), the gap is real money: Intelligent Octopus Go at 7p/kWh works out to about £190 per year for charging; Octopus Go at 9p/kWh is about £243. The £50 annual gap is meaningful, but the smart-charger requirement is a binary gate - if your kit is supported, Intelligent Octopus Go is the better tariff full stop.

Octopus Tracker is a wholesale-following tariff: every day, the rate is set by the previous day's wholesale gas and electricity prices, with no exit fees if you move away. As of mid-May 2026 the rolling average was around £1,488 per year for a typical UK household - lower than both the default price cap and the 12-month fixed.

For EV owners, Tracker works best when wholesale prices stay calm and the household is happy to flex charging to days where the rate is below 12p/kWh. The maths is straightforward: if Tracker's average daily unit rate sits below the Intelligent Octopus Go peak rate (around 24-27p/kWh on weekdays) AND you can schedule most of your charging to days the wholesale price is low, you save versus the overnight EV tariff.

The honest answer most days: Intelligent Octopus Go is the surer bet. Tracker rewards engagement (checking the app daily, scheduling around the cheap days) more than the EV tariffs do. If you don't want to think about it, the dedicated overnight tariff wins. If you enjoy optimising, Tracker can beat it - though the upside is rarely more than £100 per year on top of the Intelligent Octopus Go baseline.

Agile Octopus is half-hourly pricing: rates change every 30 minutes based on actual wholesale energy auction prices. Average household cost was around £1,520 per year mid-May 2026. For EV owners with a smart charger capable of charging in 30-minute slots (Ohme Home Pro, Zappi v2, Indra Smart Pro and others all support this), Agile can deliver charging at negative rates several times per month - the wholesale market sometimes goes negative during high wind output.

Practical reality: Agile is the highest-engagement tariff in this comparison. To get the savings, your charger needs to know how to schedule into the cheapest half-hour windows automatically. Ohme and Zappi do this well via Agile-aware automation. If your charger is on a Go-compatible list but not an Agile-aware list, stick with Intelligent Octopus Go - the extra fiddle isn't worth it.

Almost never, if you can charge overnight at home. Octopus 12M Fixed v18 in May 2026 sat at £1,632 per year - £218 below the upcoming July 2026 cap of £1,850 but still well above any of the EV-optimised tariffs once charging makes up a meaningful share of household usage. Where fixed earns its keep:

Cosy Octopus was built for heat-pump homes and gives three cheap windows per day: 04:00-07:00, 13:00-16:00 and 22:00-00:00 - plus a higher 16:00-19:00 peak that bites if you're not careful. For EV owners who also run a heat pump, Cosy is often the optimal single-tariff choice because both the heat pump and the EV can charge into the same cheap windows.

For an EV owner without a heat pump, Cosy generally loses to Intelligent Octopus Go. The cheap-window total is smaller (8 hours/day spread across three windows versus a clean 6-hour overnight block), and the 16:00-19:00 peak rate is more aggressive than Go's daytime rate.