Cosy or Intelligent Octopus Go for an EV and heat pump?

If you have both an electric car and a heat pump, compare the electricity bill for the whole home. Intelligent Octopus Go is a sensible starting point when you regularly charge a compatible EV at home. Cosy deserves a closer look when daytime heating is a large part of your electricity use and its three cheaper periods fit your home. Neither is automatically cheaper just because you own both technologies.

Octopus's smart-tariff selector usually points EV-and-heat-pump homes towards Intelligent Go. That recommendation is based on modelled usage, including an assumed charging routine and heating adjusted towards cheaper periods. Your mileage, winter heat demand and ability to shift use may be different.

What changes between the two tariffs?

Intelligent Octopus Go has a fixed whole-home off-peak window from 23:30 to 05:30 and managed charging for an eligible EV. Check your exact car or charger, smart meter and current offer before relying on it. The amount of discounted managed EV charging is subject to the tariff's allowance and conditions; it is not an extra heating allowance.

Cosy Octopus spreads its cheaper electricity periods across the day: 04:00–07:00, 13:00–16:00 and 22:00–00:00. It has a higher-priced period from 16:00 to 19:00, with a separate day rate at other times. Those rates apply to household electricity, so an EV can use the Cosy windows too. The question is whether your charging needs fit those shorter blocks alongside the heating routine.

Use each supplier page for your postcode's current rates and standing charge. This is a comparison of tariff shapes, not a promise that today's cheapest advertised charging rate produces the lowest annual bill.

Start with the home you have, not a battery you might buy

For an EV-and-heat-pump home without a battery, overnight electricity cannot simply be saved for every later hour. Heating and hot water can sometimes be timed, but the building still needs to stay comfortable throughout the day.

If you already have a home battery, it may help cover some daytime import after overnight charging. Its usable capacity, losses, output and remaining charge matter. Do not assume it can run the heat pump all day, and do not count a proposed battery as free equipment that makes one tariff win. Compare the home as it stands first.

Solar and export add another decision. Our EV, solar and battery guide covers those flows in more detail; they should not obscure the simpler EV-and-heating comparison here.

When Intelligent Go belongs on the shortlist

It is particularly worth comparing when you charge regularly at home, your exact EV or charger can be connected and a useful share of other electricity already falls within the overnight window. Hot-water timing may help, where it suits the system and household.

Do not build the heating plan around hoped-for daytime EV slots. Before shifting the heat pump or other household use outside the fixed overnight window, confirm with Octopus how your applicable tariff treats that household consumption. Then check the corresponding billed periods. A charging schedule is not, by itself, proof of the heat pump's electricity rate.

If your setup cannot use Intelligent Go, standard Octopus Go is a separate fixed-window EV option to compare, not a guarantee that it will beat Cosy for your heating demand.

When Cosy deserves the closer comparison

Cosy's afternoon window may be useful when the home needs substantial daytime heating and can move some demand ahead of the 16:00–19:00 peak without becoming cold later. It can also be worth comparing when home EV charging is relatively modest.

Look at the car as well as the heating. An EV that needs a long continuous charge may not fit a single Cosy period. Work out when you will actually be plugged in and what happens to any charging outside the cheaper windows. Do not assume all home charging receives Cosy's lower rate.

Cosy also loses appeal if considerable unavoidable heating, cooking and other electricity lands in its evening peak. Count that use rather than removing it from a spreadsheet because you hope to shift it later.

Keep the heating efficient and comfortable

Energy Saving Trust's heat-pump guidance favours steady temperatures, longer running periods and suitable flow temperatures. Cheaper electricity can make a different schedule worthwhile, but forcing large temperature swings or high-temperature recovery can change electricity consumption as well as the rate paid.

Ask your installer about a routine that suits the building and system. A tariff comparison should not require a cold house or overriding the manufacturer's safety settings. Keep hot-water hygiene controls intact.

Compare a realistic year, including winter

Use actual half-hourly meter data where available. If the heat pump is new, use the installer's estimate as an estimate, with separate winter and milder-weather assumptions. Keep ordinary household use and home EV charging in the total.

For each candidate, price the electricity that lands in each of its own bands, then include its standing charge. Do not apply the same off-peak percentage to two tariffs with different windows. If a new heating routine changes how many units the system uses, allow for that rather than pretending only the price changes.

A quiet summer week will not represent winter heating. Equally, a very cold week will not represent every month. Include periods when the car is away, charging elsewhere or not needing a top-up.

Check the switching conditions before choosing

Both routes need suitable smart-meter readings and account activation. Having compatible equipment does not prove the chosen tariff is already active after a supplier switch. Check the interim tariff and when your new rate actually begins.

Read the offer's fixed or variable status, term and any exit fee, including the effect of changing tariff within Octopus. Do not assume switching between Cosy and Intelligent Go each season is unrestricted: Octopus's current smart-tariff terms include a 30-day restriction on returning to a smart import tariff after leaving one. Ask how that applies to the move you intend before booking it.

If Octopus still suits your home after the tariff, eligibility and switching checks, the referral page explains the site's direct signup route. Existing customers should use their account's tariff options instead of starting a new-customer referral switch.