I Locked My EV Tariff at 6.6p. Here's Why That Matters—Even Though It Doesn't Look Like a Saving

I switched from Octopus Intelligent Go variable to Intelligent Go Loyalty fixed this month. The mathematics looked thin: 6.6p per kilowatt-hour, guaranteed for 12 months, versus the 7.0p I was paying on the variable rate.

A 0.4p saving. That's about £30 a year on my electricity.

But that number is a trap. It's today's number. And it's completely the wrong way to think about a tariff lock when the energy market is bracing for a 12–14% price cap spike in January.

The Rose Cottage Picture

Let me set the actual context. Rose Cottage—a stone-built rural property in Oxfordshire where I live—imported 12,483 kWh in 2025, with 88% of that between 11:30 p.m. and 5:30 a.m. That 88% figure is verified. I've got a Zappi charger that's disciplined enough to pause during the day peak, and because of that, the overnight window captures nearly all of my consumption: EV charging, heat pump defrost cycles, occasional night-time appliance runs.

Export sits at the other end: 2,580 kWh exported in 2025, climbing to 5,024 kWh in the first seven months of 2026 as the solar arrays ramped up. I'm on the Outgoing Octopus flat export rate (12p per kWh, a fair deal that beats the alternatives).

For 18 months, I've been on Intelligent Go variable because the smart tariff's game—let Octopus's machine learning find the cheapest, greenest charging window within the 11:30 p.m.–5:30 a.m. window—made sense when variable rates were stable. The 7.0p overnight rate felt solid.

Now the market is moving. And that's changed the calculation.

Why January Matters

The UK's energy price cap—which sets the ceiling for standard variable tariffs—is forecast to jump by 12–14% in January 2027. The current cap, in force until the end of 2026, sits at £1,723 for a typical dual-fuel household. Analysts are penciling in £1,932 (EDF), £1,941 (E.ON Next), and £1,970 (British Gas) for the first quarter of next year.

Those forecasts don't directly hit Intelligent Go. It's a smart tariff, outside the price cap. But smart tariffs don't exist in a vacuum. They track wholesale electricity costs. And wholesale electricity is driven by the same forces pushing the cap up: Middle East volatility, constrained gas supply, winter demand.

The pattern is familiar. In early 2022, when wholesale prices spiked, Octopus's variable smart rates followed. At Rose Cottage, I rode the volatility on Agile and Intelligent Go because I had the solar and battery to absorb the shocks. But volatility cuts both ways. When rates spike, locking protects you.

Right now, locking has no short-term appeal—your locked rate looks slightly worse than the variable rate you'd pay today. The trade-off is invisible until January arrives and doesn't. Then it becomes a visible saving.

The Math on 6.6p

Here's the cold calculation. At Rose Cottage's current usage—roughly 6,400 kWh imported in the first seven months of 2026, annualizing to about 11,000 kWh for a full year with battery helping through summer—and assuming that 88% night share continues:

That's the bet I'm taking. I'm accepting a 40-quid upside if prices hold flat, to hedge against a 180-quid downside if they spike. And the downside is more likely than the upside.

The break-even is around 7.3p per kilowatt-hour—if the variable rate averages above that over the next 12 months, I'll have locked at a profit. Given the January forecast, 7.3p feels very achievable.

Why This Tariff Exists

Intelligent Go Loyalty fixed is new, and it exists because Octopus has a problem: customers like me have seen the energy market signals and are starting to lock. If Octopus only offered the variable rate, sophisticated users would migrate elsewhere. So they've created a fixed option to keep volume.

It's priced carefully. At 6.6p, it's not cheap—it's just cheaper than the risk. Octopus has to hedge the January spike themselves. If they underprice the lock, they lose money. If they overprice it, they lose customers. 6.6p is where that meets.

The £50 exit fee is standard and, for my use case, irrelevant. I'm not planning to leave the tariff early. The annual import is stable. I've got no reason to break the lock.

The Honest Caveats

This is a bet on volatility, not a sure saving. Three things could go wrong:

Who This Is For—And Who It Isn't

If you're a Rose Cottage type—solar, battery, disciplined load-shifting, and high confidence you'll be in your current home and usage pattern for the next year—locking at 6.6p makes sense. You're trading a statistically small upside for a hedge against a more probable downside.

If you're on a standard variable tariff and thinking about switching to Intelligent Go Loyalty, you need different analysis. The smart tariff itself has a cost: it needs a compatible charger, it's reliant on Octopus's API staying up, and you lose the optionality to shift to Agile if the market moves. The fixed version on top of that locks you into 6.6p and a £50 exit fee. For someone not already living in the smart-tariff ecosystem, it's a bigger commitment.

If you're paying standard variable rates and expecting prices to fall, don't lock anything. Wait for April 2027, when analysts expect a 2% drop as summer demand arrives.

Why Now Is the Window

The key insight isn't that 6.6p is cheap. It's that January is closing. Once the price cap spike lands and variable rates rise, the lock will look retrospectively obvious. Right now, in September, when variable is still 7.0p and the spike is just a forecast, locking feels like you're overpaying for insurance.

You're not. Insurance costs money because the risk is real.

I've locked. Over the next 12 months, I'll either have paid 40 quid for peace of mind, or I'll have hedged against a spike that saved me more. Either way, I'll know by January 2027 whether it was the right call.

For now, the math says it is.