Octopus Flux vs Cosy Octopus: Which One Actually Suits Your Solar Home in 2026

I get asked some version of this question most weeks: “I’ve got solar panels — should I be on Octopus Flux or Cosy Octopus?” It’s a completely reasonable question, because the names sound like they might do a similar job. They don’t, really.

Octopus Flux is built for homes with solar panels and a battery. It pays you well for exporting stored or surplus power back to the grid at exactly the moment the grid needs it most.

Cosy Octopus is built for homes heating with electricity — a heat pump, electric boiler or electric radiators. It gives you cheaper electricity at set points in the day so your heating costs less to run. It has nothing to do with exporting solar power at all.

One tariff is about selling power. The other is about buying it more cheaply. Below, I’ve set out exactly how each one works, the current 2026 rates, who’s actually eligible, and a straight answer on which one — or which combination — fits your home. There’s also a fairly important 2026 update: one of these two tariffs currently isn’t taking new customers, and I’ll explain what that means for you.

The quick answer

What is Octopus Flux, in plain English?

Octopus Flux is a combined import-and-export electricity tariff, and it’s only really relevant if you’ve already got solar panels and a home battery. Rather than one flat rate all day, your day is split into pricing windows — but the whole point of Flux is moving energy through your battery, not running a heat pump cheaply.

Here’s the daily shape of it, taken directly from Octopus’s own tariff page:

• 02:00–05:00 — the cheapest window. Good for topping your battery up from the grid if solar alone hasn’t filled it.
• 16:00–19:00 — the peak window, and the one that actually matters. This is when you’re paid the most for exporting stored or surplus solar power back to the grid.
• Everything else — a standard rate that sits between the two.

With standard Octopus Flux, you schedule your own battery — charging it overnight and discharging it at peak. With Intelligent Octopus Flux, Octopus takes that scheduling off your hands entirely and controls a compatible battery automatically, aiming to squeeze the most value out of every day.

I’ve broken all five Octopus export tariffs down side by side, with the full current rate table, in my Octopus Energy solar export tariff guide — worth a look if Flux turns out not to suit your setup, since Outgoing Octopus and Agile Outgoing are both explained there too.

What is Cosy Octopus, in plain English?

Cosy Octopus is a completely different kind of tariff. It’s built for homes heating with electricity — air or ground source heat pumps, electric boilers, and electric radiators. It’s purely an import tariff: what you pay for electricity coming in. It doesn’t touch solar export at all, and you don’t need solar panels to join it.

Instead of a flat rate, Cosy gives you three “Cosy Hours” windows a day, plus a peak window:

• 04:00–07:00, 13:00–16:00 and 22:00–00:00 — three off-peak windows, roughly 51% cheaper than the standard day rate in your region. Eight hours of cheap electricity in total, every day.
• 16:00–19:00 — the peak window, roughly 50% higher than the standard day rate.
• Everything else — the standard day rate for your region.

So, as an illustration: if your region’s day rate happens to sit around 26p/kWh, Cosy Hours would land somewhere around 13p/kWh, and the peak window around 39p/kWh. Those are illustrative figures only, since Cosy’s rates are set per region and updated quarterly — always check your own postcode for the exact number.

Octopus’s own modelling puts the typical saving at around £82 a year on electricity for a heat pump household moving from its standard tariff to Cosy’s fixed product, based on annual consumption of 5,877kWh. That’s specifically Octopus’s electricity-only comparison for its own fixed tariff. The wider real-world saving from moving a heat pump onto a dedicated tariff like Cosy — rather than a standard variable rate — tends to run higher once you look at the full running-cost picture; I’ve modelled this closer to £200–£400 a year in my heat pumps in the UK guide, depending on how much heating and hot water you can shift into the cheap windows.

Flux vs Cosy: the head-to-head

What the numbers actually look like

The chart above is worth sitting with for a second, because it’s easy to glance at “up to 29.32p” for Flux and “~39p” for Cosy’s peak and assume Cosy is the pricier tariff overall. It isn’t quite that simple. Flux’s headline figure is money coming in — what you’re paid to export. Cosy’s headline figure is money going out — what you pay to import. They’re measuring opposite directions of energy flow, which is really the single most important thing to keep in mind when people bundle these two tariffs together in comparison articles.

Worked examples: what could you actually earn or save?

Scenario A — solar + battery, on an Octopus export tariff

Using the figures from my Octopus export tariff guide: a typical 4kWp system exporting 1,200kWh a year earns around £144 on flat-rate Outgoing Octopus at 12p/kWh, versus just £49 on the basic 4.1p SEG-only rate. If every one of those units could instead be exported at Flux’s 29.32p peak rate, that’s worth roughly £352 on paper. In practice you won’t hit that ceiling on every unit — you’re only exporting at the best rate for the kWh your battery can actually hold and discharge inside the 16:00–19:00 window, so your real blended rate across the year will usually land somewhere between the 12p flat rate and the 29.32p peak figure, not right at the top of it.

Scenario B — heat pump home, on Cosy Octopus

Octopus’s own figures suggest around £82 a year in electricity savings for a typical heat pump household switching to Cosy Fixed, and my own running-cost modelling in the heat pumps guide puts the wider saving (heat pump on a dedicated tariff vs a standard variable rate) closer to £200–£400 a year, depending how much of your heating and hot water you can shift into the three Cosy Hours windows.

Want your own numbers rather than a national average? My free SEG income estimator will give you a personalised export income estimate based on your system size, roof orientation and self-consumption.

Can I be on both tariffs at once?

Not exactly, and this catches people out. Cosy is an import tariff. Flux is a combined import and export tariff. But you can only have one electricity import tariff live on your meter at any given time — so if your home has solar, a battery and a heat pump, you have to pick a priority. Here’s how I’d think it through:

Is Octopus Flux available right now? (2026 update)

Cosy Octopus, by contrast, is open as normal and carries no exit fees, so there’s no equivalent waiting game if a heat pump is what you’re weighing up.

Eligibility checklist, side by side

Thinking about adding a battery specifically to qualify for Flux? My solar battery storage guide runs through real 2026 installed costs and payback periods before you commit to anything.

Government schemes and rules that affect this decision

Neither tariff exists in a vacuum — both sit on top of wider UK government policy, and it’s worth knowing the framework:

• Smart Export Guarantee (SEG): the government scheme requiring large suppliers to pay for exported solar electricity, which is the legal basis Flux (and every other Octopus export tariff) sits on. Full rules are on the official GOV.UK Smart Export Guarantee page.
• Boiler Upgrade Scheme (BUS): if you’re weighing up a heat pump specifically to access Cosy, this is the £7,500 government grant (£9,000 for oil/LPG homes until 31 March 2027) that reduces the upfront cost. Details and eligibility are on the GOV.UK Boiler Upgrade Scheme page.
• 0% VAT on qualifying installs: both a battery (for Flux eligibility) and a heat pump (for Cosy eligibility) currently qualify for 0% VAT until 31 March 2027. Check what you personally qualify for with the UK Solar Grant & VAT Savings Checker.
• The Ofgem price cap: Ofgem confirmed the price cap rose to £1,862/year from 1 July 2026, up around 13% on the previous quarter — see Ofgem’s official announcement. That rise is exactly why both Flux’s export value and Cosy’s off-peak saving matter more this year than last, and I go through what it means for solar payback in more depth in my energy price cap guide.

Pros and cons, honestly

My verdict

If I’m honest, this isn’t really a straight “versus” at all once you look past the marketing names — it’s two tools for two different jobs, and most households only need one of them. If your solar panels are the main thing and you’ve got a battery sat there capable of holding charge until the evening, Flux (when it reopens) is the one worth watching. If your main cost driver is a heat pump working overtime through a British winter, Cosy is worth joining today — there’s no fee and no risk in trying it. And if you’ve genuinely got both a battery and a heat pump, don’t feel like you need to pick a “winner” between the two guides you’ve read online — run Cosy for your heating and bolt on a plain export tariff for your solar, and revisit Flux once it’s open again.

Not sure what size solar and battery setup you actually need before any of this becomes relevant? My solar panel calculator is free to use, and if you’re ready to get quotes, my find an MCS-certified installer tool is a fast way to compare a few before committing.

Frequently asked questions