Octopus Cosy Tariff for Heat Pumps: Is It Worth Switching?

The Octopus Cosy tariff is one of the best-kept open secrets in the heat pump world. If you have a heat pump and you’re still on a standard electricity tariff, you’re likely overpaying by several hundred pounds a year. The Octopus Cosy tariff is specifically designed around the usage patterns of heat pump households — and understanding how to use it properly can make a meaningful difference to your annual energy bill.

What Is the Octopus Cosy Tariff?

The Octopus Cosy tariff is a time-of-use electricity tariff from Octopus Energy, designed for homes with heat pumps. Rather than charging a flat rate per kWh throughout the day, it offers significantly cheaper electricity during specific off-peak periods, with higher rates at peak times.

The core idea: heat pumps don’t need to heat your home at a specific clock time — they can pre-heat during cheap periods and coast through the expensive ones. A well-programmed heat pump on the Cosy tariff runs hard during cheap windows, stores heat in the thermal mass of the building and in the hot water cylinder, and reduces output during peak pricing. The result is the same comfortable house, at substantially lower cost.

Octopus Energy has grown rapidly in the UK and is now one of the largest domestic energy suppliers. They’ve invested heavily in smart tariff products designed to shift demand away from peak grid periods — which benefits consumers, benefits Octopus, and benefits the grid. Cosy is their heat-pump-specific offering.

How the Octopus Cosy Tariff Works

The tariff currently has three price periods:

Cosy hours (cheapest) — typically 4 hours per day, split into two windows: early morning (around 04:00–07:00) and afternoon (around 13:00–16:00). Rates in these windows are significantly below the standard cap rate, often in the range of 10–14p/kWh.
Standard hours — the bulk of the day, charged at a rate comparable to the Ofgem price cap.
Peak hours (most expensive) — typically 16:00–19:00, when grid demand is highest. Rates can be significantly above the standard rate, sometimes 38–45p/kWh.

Note: specific rates change regularly as Octopus updates the tariff. Always check the current rates directly on octopus.energy before switching. The structure — cheap morning, cheap afternoon, expensive evening — has remained consistent.

Eligibility: Who Can Get Octopus Cosy?

To join the Cosy tariff, you need:

A heat pump — the tariff is specifically for heat pump households. Octopus may ask for confirmation during sign-up.
A smart meter — Octopus needs to read your consumption in half-hour intervals to apply time-varying rates. If you don’t have a smart meter, Octopus can arrange installation.
Octopus Energy as your supplier — you need to be an Octopus customer, or switch to them. Switching is straightforward and handled by Octopus with no gap in supply.

There are no other significant restrictions. You don’t need a specific make of heat pump, a particular age of system, or any special controls. However, as described below, you’ll get more value from the tariff if your heat pump has good scheduling capabilities.

The Real Bill Impact: What Can You Actually Save?

The savings depend heavily on how much of your heat pump’s consumption falls within Cosy hours, and whether you successfully shift usage away from peak periods. In practice:

A heat pump that is well-optimised for Cosy hours can see 40–60% of its electricity consumption fall within cheap windows, delivering effective electricity rates significantly below the standard cap.
Octopus has published data suggesting average bill savings of £200–£500/year for heat pump households switching to Cosy from a standard tariff — though this varies significantly with property size, insulation quality, and how actively the household manages the system.
The peak penalty (expensive evening rates) is the risk. If your household uses a lot of electricity between 16:00 and 19:00 — electric showers, ovens, electric vehicle charging — you can end up paying more on Cosy than on a flat-rate tariff. Heat pump consumption itself can usually be shifted away from peak, but other household loads cannot always be.

The honest calculation: add up your likely cheap-hour and peak-hour usage, multiply by the relevant rates, and compare to a standard tariff. Octopus provides a calculator on their website. For most heat pump homes that can shift evening electricity use, Cosy is a clear win.

For context on what heat pump running costs look like overall, see our Heat Pump Costs guide and Savings Calculator.

How to Set Your Heat Pump to Use Cosy Hours

Getting value from Cosy requires more than just switching tariff — you need to programme your heat pump to pre-heat during the cheap windows and reduce demand during peak times. Here’s how to approach it:

Space Heating Schedule

Set your heat pump’s heating schedule to run at full target temperature during the early-morning Cosy window (04:00–07:00). The thermal mass of your home and radiators will retain heat for several hours. By 16:00 when peak pricing starts, the house should still be close to comfortable temperature — if your insulation is reasonable, you may not need the heating to run much at all until the peak window closes at 19:00.

During the afternoon Cosy window (around 13:00–16:00), the heat pump can top up the building temperature and heat the hot water cylinder. This acts as pre-heating before the expensive evening period.

Hot Water Schedule

Set your hot water cylinder to heat during Cosy hours — either the morning or afternoon window, or both. Most modern heat pump controllers allow you to set specific time windows for hot water heating. Aim to have the cylinder fully heated before the 16:00 peak starts. A well-insulated cylinder loses only a few degrees over a 4–6 hour period, so hot water heated at 13:00 will still be available at 19:00.

Weather Compensation and Flow Temperature

Weather compensation — where the heat pump automatically adjusts its flow temperature based on outdoor temperature — is compatible with Cosy and helps efficiency. However, avoid the temptation to turn off weather compensation in favour of aggressive pre-heating; running at unnecessarily high flow temperatures during Cosy hours trades efficiency for tariff savings, and the net result may not be worth it.

Our Heat Pump Efficiency guide covers flow temperature settings in detail.

Smart Controls and Integration

Some heat pump controllers integrate directly with Octopus tariff data via the Octopus API, automatically adjusting operation based on real-time prices. Brands including Vaillant (with the myVAILLANT app), Daikin (Daikin Residential Controller), and several third-party smart thermostats support this. If your heat pump controller supports API integration, setting this up is well worth the effort — it removes the manual scheduling burden entirely.

Who Benefits Most From Octopus Cosy?

The households that see the biggest savings share a few characteristics:

Well-insulated homes — higher thermal mass and lower heat loss mean the building retains pre-heated warmth longer, so the heat pump needs to run less during peak hours.
Large hot water cylinders — more storage means more cheap electricity can be banked as hot water.
Flexible daytime schedules — households where someone is at home during afternoon Cosy hours can benefit more, since cooking and other loads can also be shifted.
Programmable heat pump controllers — you can get value from Cosy with a basic time-clock, but smart thermostats and API-integrated controllers unlock much more of the potential saving.

The households that benefit least are those with high evening electricity demand that cannot be shifted — for example, homes with electric showers, induction hobs, and EV charging that all happen to concentrate in the 16:00–19:00 window.

Octopus Cosy vs Other Heat Pump Tariffs

Octopus Energy offers several tariffs relevant to heat pump households, including Agile Octopus (variable half-hourly prices matching wholesale market rates) and Octopus Go (a simpler cheap overnight window). Cosy is specifically tuned for heat pumps with its two daily cheap windows that align well with morning and afternoon heating cycles.

Other energy suppliers are increasingly offering their own smart tariffs for heat pump customers, and the market is developing. The Energy Saving Trust maintains an updated list of smart tariff options for heat pump households. Always compare your specific usage pattern against available tariffs rather than assuming Cosy is automatically the best option for your household.

That said, Cosy has been purpose-designed for heat pump use and has a strong track record. For most heat pump households considering a tariff switch, it’s the obvious starting point.

Making the Switch

Switching to Octopus Energy and signing up for Cosy takes around 10 minutes online. Octopus handles the switch from your current supplier. If you need a smart meter, they’ll arrange an appointment — smart meter installation is free. You can switch back if the tariff doesn’t work for you, though it’s worth giving it at least one full heating season to assess properly.

Before switching, run through the bill impact calculation on octopus.energy using your current annual consumption figures (available from your current supplier or from your smart meter). This gives you a realistic estimate of what to expect rather than relying on headline saving figures that may not reflect your usage pattern.

For a broader view of how to reduce heat pump running costs, see our comparison of heat pump vs gas boiler running costs in 2026 and our Efficiency guide.