How do I use a time of use tariff?
Time of use, smart electricity tariffs vary the price depending on when you consume energy. Typically there's a period which is cheaper (off-peak), often at night when demand on the grid is lower. This is balanced by a slightly more expensive peak rate outside these hours.
By moving a significant proportion of your consumption (load) into that period, often overnight, you can save money (e.g. charging your EV).
A Vimma battery automatically charges when it's cheap, then powers your home during the more expensive period. By buying when it's cheap and avoiding the higher cost period (arbitrage) you save a chunk!
- Buy cheap: The battery charges overnight at, say, 7–10 p/kWh
- Use smart: It discharges during the day to avoid peak rates
- Result: Hassle free savings!
It’s the ultimate set-and-forget energy arbitrage.
What should I watch out for?
When comparing tariffs, check the terms:
- Electric Vehicle - Some tariffs require you to have an EV or at least a home charger, others don't. The energy supplier may ask for evidence.
- Device control - Some tariffs require you to give control of your EV charger or battery to the energy supplier. These are often known as agile tariffs.
- Compatibility - Vimma is not compatible with tariffs which control the battery. Controlling the EV or charger is fine providing you can charge the battery when it's cheap too.
- Period and rate - A fixed low cost window of 1 to 4 hours is required to charge depending on what size Vimma you have. Most periods are longer than this, but look closely at the unit rate and length of the off-peak period.
- Other charges - Watch out for increased peak rate charges and standing charges when comparing.
Which work best with Vimma?
Don't have an EV?
- E.ON Next: Drive
- Octopus: Go
Both tariffs deliver battery‑friendly off‑peak windows without requiring an EV, charger, or supplier control, making them perfect fits for Vimma.
Got an EV already?
- SO Energy: SO EV
- British Gas: Charge Power
- EDF: GoElectric
These tariffs require you to have an EV, but if you've already got one, great! You can consider these to work with your Vimma too.
Other things to watch out for
- Dynamic tariffs require smart meter
- Always check eligibility fine print (not all EV tariffs require a car)
- Make sure Vimma retain full control of the battery