Should I be on a time-of-use or EV tariff with solar?
If you have solar plus a battery or an electric vehicle, a time-of-use tariff usually saves more than a flat tariff. You charge the battery or car cheaply overnight (often under 10p per kWh), then use free solar and stored energy by day, and export at peak rates. Without a battery or EV, a simple tariff with a strong export rate is often best.
How solar and smart tariffs combine
- Charge a battery or EV overnight at a low off-peak rate.
- Run the home on free solar during the day.
- Export surplus solar when export rates peak.
- Top up from the battery in the evening instead of buying at peak.
Who benefits most
Households with an EV and a battery gain the most, because cheap overnight charging plus daytime solar can slash both fuel and electricity bills. An EV typically adds 2,000 to 3,500 kWh to annual usage, which a larger solar system and smart tariff help cover. SunSum's calculator lets you flag an EV or heat pump so the system size reflects it.
Frequently asked questions
- Do I need a battery to benefit from a time-of-use tariff?
- A battery or an EV makes time-of-use tariffs most worthwhile, because both let you shift cheap off-peak energy into peak times.
- Can solar charge my EV directly?
- Yes. Many EV chargers can be set to use surplus solar, charging the car for free when the panels are generating more than the home is using.
Related questions
Indicative estimates based on UK average data. Last updated 27 May 2026.