Octopus Cosy tariff review (UK, 2026): is it worth it?
A practical, UK-specific guide to Octopus Cosy: how the off‑peak heat pump windows work, who it suits, what to watch for, and how to compare it fairly with other tariffs.
- Designed for heat pumps: multiple off‑peak windows, not just one overnight slot
- Works only with a smart meter and compatible set‑up (eligibility can vary)
- Best judged on your likely “shifted” usage, not headline unit rates alone
Figures are illustrative and will vary by region, meter, and Octopus terms. Always check your personalised rates and eligibility before switching.
Fast answer: is Octopus Cosy a good tariff in 2026?
Octopus Cosy can be a strong option if you have (or are installing) a heat pump and can reliably move a meaningful share of electricity use into Cosy’s off‑peak windows. It’s less compelling if you can’t shift demand, if your home relies heavily on peak‑time electric heating, or if your set‑up can’t consistently “pre‑heat” without comfort issues.
Best for
- Homes with an air/ground source heat pump
- Smart meter households that can shift usage
- Homes that can pre‑heat (thermal mass / good insulation)
Watch outs
- Eligibility and tariff availability can change
- Peak unit rates may be higher than a standard tariff
- Comfort can suffer if schedules are too aggressive
What to do next
- Check you have a working smart meter
- Estimate your off‑peak share (heat pump + hot water)
- Compare against whole‑of‑market quotes
Important: Octopus Cosy is a time‑of‑use electricity tariff. Your bill depends on when you use electricity, not only how much. Always check your exact unit rates and standing charge for your postcode area.
How Octopus Cosy works (plain English)
Cosy is built around the idea that heat pumps can run a bit harder during cheaper periods (to “charge” your home’s warmth), then run less during expensive periods. Unlike many time‑of‑use tariffs that mainly offer one overnight cheap window, Cosy typically provides multiple cheaper windows spread across the day (exact times and prices can vary by product version and region).
What you normally need
- A working smart meter that can send half‑hourly readings (SMETS2 is common, but functionality can vary)
- Electricity supply on a tariff that uses time bands (Cosy is electricity‑based; any gas supply is separate)
- A heat pump (or planned installation) to get the most value from the cheaper windows
- Ability to shift demand (heating/hot water schedules, possibly EV charging or appliances if suitable)
How you can “win” on Cosy
- 1) Move heat pump run-time into cheap windows
- Set heating/hot water schedules so more kWh land in the lower-priced bands (without making the home uncomfortable).
- 2) Reduce usage in peak bands
- Avoid high-consumption activities at peak where possible (e.g., tumble dryer, immersion heater, EV charging).
- 3) Keep settings realistic
- Over-aggressive pre-heating can backfire if it increases total kWh use (or triggers resistive backup heating in some systems).
Caveat for 2026: Tariff names, time bands, and eligibility rules can change over time. Treat any “window” examples as typical patterns, then confirm the exact bands and rates in your personalised quote and tariff terms.
Compare Cosy vs other UK tariffs (whole of market)
If you’re considering Cosy, it’s worth checking fixed and other time‑of‑use options too. Submit your details to get a tailored comparison.
Two quick checks before you decide
- Smart meter working? Time‑of‑use tariffs usually require half‑hourly readings to be received reliably.
- Can you shift heating? If most of your heat pump consumption happens at peak times, Cosy may cost more than a flat-rate tariff.
Realistic scenarios (illustrative numbers)
These examples show why off‑peak share matters. We use simple maths so you can replicate it with your own rates. Assumptions are listed under each scenario and exclude standing charges to keep the comparison focused on unit rates.
Scenario A: well‑set heat pump schedule (Cosy likely helps)
A home shifts a good chunk of heat pump and hot water into cheaper windows.
- Monthly electricity use: 900 kWh (typical for an all‑electric heat pump home in colder months)
- Off‑peak share on Cosy: 55% (495 kWh) | Peak: 45% (405 kWh)
- Illustrative Cosy rates: Off‑peak 18p/kWh, Peak 36p/kWh
- Comparison flat tariff: 28p/kWh
| Cosy energy cost (excl. standing charge) | £233.10 |
| Flat tariff energy cost | £252.00 |
| Illustrative difference | ~£18.90/month cheaper |
Calculation: (495×£0.18) + (405×£0.36) vs (900×£0.28). Your actual rates and standing charges will change the outcome.
Scenario B: limited shifting (Cosy may not suit)
A home struggles to pre‑heat (e.g., draughty property, comfort constraints), so most usage remains in peak.
- Monthly electricity use: 650 kWh
- Off‑peak share on Cosy: 20% (130 kWh) | Peak: 80% (520 kWh)
- Same illustrative Cosy rates: Off‑peak 18p/kWh, Peak 36p/kWh
- Comparison flat tariff: 28p/kWh
| Cosy energy cost (excl. standing charge) | £210.60 |
| Flat tariff energy cost | £182.00 |
| Illustrative difference | ~£28.60/month more |
Calculation: (130×£0.18) + (520×£0.36) vs (650×£0.28). Even small shifts can change the result; check your half‑hourly data if you can.
Standing charges: always include them when deciding. A tariff with a slightly better unit rate can still be worse overall if the standing charge is higher for your region.
Cosy vs other tariff types (what to compare)
Use this table to compare structures rather than brand names. Actual prices vary by region and change over time.
| Tariff type | How pricing works | Best for | Key risk |
|---|---|---|---|
| Octopus Cosy (time‑of‑use) | Different unit rates across several daily time bands (cheap windows + peak) | Heat pump households that can shift a meaningful share to cheap windows | If you can’t shift usage, peak rates can outweigh off‑peak savings |
| Single‑rate (flat) fixed | Same unit rate all day, locked for a term (standing charge may vary) | People who want predictability and don’t want to manage time bands | Exit fees and missing out if market prices drop |
| Single‑rate variable | Same unit rate all day; supplier can change rates (within rules) | Flexibility without exit fees (often), lower commitment | Price changes can increase bills; not tailored for heat pumps |
| Economy 7 / two‑rate | Cheaper night rate for a set number of hours, higher day rate | Storage heaters, immersion heating, some EV charging patterns | If you don’t use enough at night, it can be more expensive overall |
Decision checklist: Cosy is likely to suit you if…
- You have a heat pump and can schedule hot water sensibly
- You can keep comfortable while shifting demand (insulation helps)
- Your smart meter reliably submits half‑hourly readings
- You’ve checked the standing charge for your region
Cosy may not suit you if…
- You can’t shift usage (work from home with daytime demand, comfort constraints)
- Your heating frequently relies on resistive backup (immersion / direct electric) at peak times
- Your smart meter data is unreliable or you’re in the middle of a meter issue
- You prefer simple bills and don’t want to manage time bands
Costs, exclusions, and common pitfalls (UK-specific)
Time‑of‑use tariffs reward the right pattern. Here are the most common issues we see when people try to judge Cosy quickly.
1) Ignoring standing charges
Standing charges vary by region and can materially affect the result—especially for lower‑use homes.
2) Overestimating how much you can shift
If your property loses heat quickly, aggressive pre‑heating may increase total kWh (and cost) rather than reduce it.
3) Hot water settings that trigger expensive backup heating
Some systems use immersion as backup. If it runs during peak, it can wipe out off‑peak gains.
4) Smart meter data problems
If half‑hourly reads aren’t received, time‑of‑use billing can be delayed or estimated. Resolve meter issues first.
5) Assuming it’s automatically best for EV charging
Cosy is designed around heating windows. EV-focused tariffs may have different cheap periods that suit charging better.
6) Exit fees / contract terms (if fixed)
Some tariffs include exit fees or eligibility requirements. Always read the tariff’s Key Terms before switching.
Payment method: If you pay by Direct Debit, you may see different prices than other payment methods. Also consider how your monthly Direct Debit is set—suppliers can adjust it based on usage and account balance.
Octopus Cosy FAQs (UK, 2026)
Do I need a smart meter for Octopus Cosy?
In most cases, yes. Time‑of‑use tariffs typically rely on half‑hourly smart meter readings to bill you correctly across different time bands.
Is Cosy only for heat pumps?
It’s designed with heat pump usage in mind. You might still use it without a heat pump, but the value usually comes from shifting large heating and hot water loads into cheaper windows.
Will Cosy definitely reduce my bill?
No. Savings aren’t guaranteed. If you can’t shift enough usage to off‑peak windows (or your peak rate is significantly higher), Cosy can cost more than a flat tariff.
Do the off‑peak times stay the same year‑round?
Time bands are defined in the tariff terms, but suppliers can change products over time. Always check your current tariff information and app/statement for your exact band times.
What if I have gas as well as electricity?
Cosy is about electricity pricing. If you have a separate gas supply, it will be billed on its own tariff. For heat pump homes, gas is often not used for space heating—but setups vary.
Can I use Cosy with solar panels or a home battery?
Possibly, but the economics depend on your export arrangements, battery size, and when you generate/use power. You’ll want to compare your import/export rates carefully and consider whether the tariff’s cheap windows align with charging needs.
Is there an exit fee?
It depends on the specific tariff version and whether it’s fixed. Check your tariff’s Key Terms and your account details before switching.
How do I compare Cosy fairly against a fixed tariff?
Estimate your off‑peak share (from smart meter data if possible), then calculate a blended rate: (off‑peak kWh×off‑peak rate + peak kWh×peak rate) ÷ total kWh. Then add standing charges for a like‑for‑like annual comparison.
Trust, methodology, and sources
Page details
- Written by: EnergyPlus Editorial Team
- Reviewed by: Energy Specialist
- Last updated: February 2026
How we assess Octopus Cosy (and similar tariffs)
We focus on customer outcomes, not marketing claims. Our review framework looks at:
- Eligibility & compatibility: smart meter requirement, time‑of‑use billing practicality, typical household fit
- Cost drivers: peak vs off‑peak rates, standing charges, how sensitive results are to off‑peak share
- Risk & effort: comfort trade‑offs, setup complexity (schedules), likelihood of bill surprises
- Comparability: we encourage blended-rate comparisons plus standing charges for like‑for‑like annual figures
Limitations (what this page can’t do)
- We can’t publish one “UK-wide” Cosy price: electricity rates vary by region, meter type, and product version.
- We can’t guarantee eligibility or acceptance; suppliers may change criteria or availability.
- We can’t know your true off‑peak share without your half‑hourly usage pattern and heating controls.
Independent UK sources we rely on
- Ofgem (energy regulator: rules, switching, consumer protections)
- Citizens Advice energy guidance (billing, complaints, switching help)
- GOV.UK: Boiler Upgrade Scheme collection (heat pump support overview; eligibility and details may change)
- GOV.UK: switching energy supplier (process and consumer rights)
We recommend checking your supplier’s tariff terms directly for exact time bands, rates, and exit fees.
Ready to compare Octopus Cosy against the market?
Get a tailored comparison using your postcode and usage profile. We’ll show options that may suit heat pump households, including time‑of‑use and fixed tariffs.
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