How it is calculated
- Flat annual cost = annual charging energy × flat rate.
- Time-of-use cost uses a weighted rate based on the entered off-peak share and the remaining peak share.
12 · Electricity tariffs
Compare flat and time-of-use charging rates
Compare an annual EV charging energy bill at a flat rate with a mix of peak and off-peak charging. Use the proportion you can actually schedule inside the provider's off-peak window.
Your inputs
Get your result
Use your own figures or load the worked example below. All calculations stay in this browser.
The estimate compares charging energy only. Confirm tariff windows, household fees, and eligibility with your electricity provider.
How to use this tool
- Enter annual charging energy and the current flat rate in one currency.
- Add the off-peak share and both time-of-use rates.
- Calculate the annual difference, then check household usage, standing charges and tariff eligibility before switching.
Worked example
Shift 70% of charging off-peak
- Annual charging energy
- 3000 kWh / year
- Current flat rate
- 0.25 per kWh
- Share charged off-peak
- 70 %
- Off-peak rate
- 0.12 per kWh
- Peak rate
- 0.35 per kWh
- Currency display
- US dollar ($)
Expected result $750 flat · $567 time-of-use · $183/year potential saving
The weighted rate is 70% × $0.12 + 30% × $0.35 = $0.189/kWh. 3,000 × $0.189 = $567, compared with $750 at the flat rate.
Transparent estimates
How to read this result
A positive saving means lower EV energy spend in this model; an increase means the time-of-use mix costs more. This does not establish whether the entire household bill would fall.
Assumptions
- The same total charging energy is used in both scenarios; the selected share can be moved into the off-peak window.
What this estimate cannot tell you
- Standing charges, export rates, household consumption, and provider-specific eligibility are excluded.