The cheapest quoted interval is not your annual electricity price. What matters is the price when you actually consume.
Know what changes
Dynamic tariffs expose the energy component to changing market prices. Read the supplier’s pricing formula and billing interval rather than assuming every offer works the same way. Check the required metering arrangements with the supplier and meter operator.
Measure useful flexibility
List consumption that can realistically move, such as some vehicle charging. Separate it from demand you cannot shift. A heat pump or battery does not automatically make a tariff worthwhile; operating constraints and comfort still matter.
Compare the complete bill
Include fixed charges, supplier fees, metering costs and any automation needed. Test your actual interval consumption against a plausible range of prices, not just cheap examples. Ask how you will see price changes, what happens during expensive periods and how you can leave the contract.
Calculate the price you actually pay
For a simple two-period example, buying 4 kWh at €0.15/kWh and 6 kWh at €0.35/kWh costs €2.70. The consumption-weighted price is €0.27/kWh, not the €0.25 arithmetic average of the two prices. Apply that logic to the contract’s billing intervals and add charges not already included. A chart of low market prices is not a calculation of your household’s annual bill.
Put a limit on useful flexibility
Identify how many kWh you can move and the hours in which they can move. A car required early in the morning has a charging deadline; hot-water and heating schedules have comfort limits. Check whether the controller can enforce these boundaries and what happens if a price feed or internet connection fails. Automation should implement a household plan rather than chase the lowest price regardless of the consequences.
Compare a difficult month as well as a good one
Ask for a historical comparison using your demand profile and a conventional tariff over the same period. Then test a scenario with fewer cheap intervals or less available flexibility. Include subscription, metering and control costs without double-counting charges already in the rate. Record the contract’s notice period and the process for changing offers so the financial comparison includes practical exit arrangements.
Your planning checklist
- Full pricing formula and billing interval understood.
- Required meter and its charges confirmed.
- Shiftable kWh, deadlines and comfort limits recorded.
- A whole-bill comparison including an unfavourable scenario.
Common questions
Does a negative market price mean my bill is negative?
Not necessarily. Market energy is only part of the retail pricing formula. Other components and fixed charges may still apply. Use the supplier’s complete terms to calculate what that interval costs you.
Is a home battery required?
No. The useful flexibility may come from other loads, such as scheduled vehicle charging. Equally, owning a battery does not guarantee a saving. Evaluate the consumption pattern and complete tariff costs first.