How to Choose an Energy Tariff for Solar Panels, Batteries and Electric Cars
Choosing an energy tariff used to be mainly about comparing one unit rate with another. For homes with solar panels, battery storage or an electric car, the calculation can be more complicated.
Some households buy electricity from the grid, generate their own power, store electricity and export surplus energy. They may also move a large part of their consumption to cheaper hours.
This means the cheapest looking tariff is not automatically the best match for every home.
Start with your household’s energy setup
Before comparing tariffs, identify which technologies your home uses and when they consume or generate electricity.
A home with only solar panels has different requirements from a home with solar panels, a battery and an electric vehicle. One may benefit most from a strong export rate, while another may gain more from cheap overnight electricity.
The main information to collect includes:
- Annual electricity consumption
- The times when most electricity is used
- Annual solar generation
- The amount of solar electricity exported
- Battery capacity and charging pattern
- Electric car mileage and charging requirements
Your smart meter or energy account may provide half hourly consumption information. Solar and battery apps can also show how much electricity is being generated, stored and exported.
Understand import and export tariffs
An import tariff covers the electricity you buy from the grid. An export tariff pays you for eligible electricity sent back to the grid.
These are separate parts of the calculation.
A supplier may offer an attractive export rate but charge more for imported electricity. Another may offer cheaper overnight charging but a lower export payment. The better option depends on how much your home imports and exports.
For example, a household that exports a large amount of solar electricity may place more value on the export rate. A household that consumes most of its solar generation at home may need to focus more heavily on import prices.
Solar panels and the Smart Export Guarantee
The Smart Export Guarantee allows eligible households in England, Scotland and Wales to receive payment for renewable electricity exported to the grid.
Payments do not begin automatically when solar panels are installed. The householder must apply for an eligible export tariff.
A smart meter capable of recording exported electricity is normally required. Suppliers may also request proof that the solar installation and installer meet the required certification standards.
There is no single national Smart Export Guarantee rate. Suppliers set their own rates, terms and eligibility conditions. Export tariffs may be fixed or variable, and some of the strongest rates may require the household to buy its imported electricity from the same supplier.
The Energy Saving Trust’s Smart Export Guarantee guide explains the eligibility requirements and application process.
Solar panels with battery storage
A home battery can store surplus solar electricity for use later in the day. It can also potentially charge from the grid during a cheaper tariff period.
For households with solar panels and a battery, Energy Saving Trust suggests considering either:
- A dedicated solar and battery tariff
- A suitable export tariff combined with a dynamic or Economy 7 import tariff
There is no universal winner between these arrangements. The outcome depends on the system size, household consumption and how effectively the battery is scheduled.
Battery storage also involves an upfront cost. Energy Saving Trust estimates that a typical 5kWh battery system costs around £4,600, although prices vary widely. A battery should therefore be assessed as a long term purchase rather than judged only by one month of tariff savings.
The organisation also notes that a typical battery may last around 10 to 12 years, which is generally shorter than the working life of solar panels.
What is a time of use tariff?
A time of use tariff charges different electricity rates at different times.
Economy 7 usually provides one cheaper overnight period. Other smart tariffs may include several price periods, while dynamic tariffs can change prices every half hour according to conditions in the electricity market.
These tariffs can work well when a household can move significant consumption into cheaper periods. This might include:
- Charging an electric car overnight
- Charging a home battery
- Running a dishwasher or washing machine
- Heating water
- Using certain electric heating systems
However, the peak rate may be higher than a standard tariff. A household that cannot change when it uses electricity could pay more despite having access to a cheap overnight period.
Choosing a tariff for an electric car
EV tariffs usually offer a reduced electricity rate during the early hours of the morning. This can make home charging cheaper when most charging can be scheduled within that window.
The key question is whether the cheap period is long enough to supply the energy the vehicle regularly needs.
Check the EV’s battery size, average weekly mileage, charger speed and the number of hours available at the lower rate. Also compare the tariff’s daytime rate and standing charge because the same tariff normally supplies the rest of the home.
An EV tariff is not automatically cheaper for every driver. Someone with low mileage or regular free workplace charging may receive less benefit than a high mileage driver who charges mainly at home.
SaveAmp’s EV vs Petrol Cost Calculator can help compare estimated running costs based on mileage and the figures entered.
Look at the whole tariff
The best tariff is the one that works with your complete energy pattern. Before changing, compare:
- Daytime and off peak import rates
- Export rates
- Standing charges
- Length of cheap periods
- Exit fees
- Fixed or variable terms
- Smart meter requirements
- Technology and charger compatibility
- Any requirement to use one supplier for both import and export
It is also worth checking how much work is required from you. Dynamic tariffs and battery scheduling may reward flexibility, but a simpler tariff could suit someone who does not want to monitor prices or adjust settings regularly.
Solar panels, batteries and electric cars do not automatically make one type of energy tariff best. Each technology changes when electricity is bought, used, stored or exported.
A useful comparison should therefore begin with your real energy pattern. Compare the value of cheap imports and export payments together, then consider how easily your household can move consumption to different times.
That provides a more realistic answer than choosing a tariff because it carries a solar, battery or EV label.
