Time-of-Use Electricity Cost & Peak Shaving Calculator
Is a time-of-use tariff actually cheaper for you? Compares it against flat rate on your own usage pattern, then shows what moving one load into a cheaper window is worth over a year.
Your tariff
Filled in from your country as a starting point. Real tariffs differ between suppliers even in the same town, so put your own rates in if you have a bill to hand.
The expensive band, usually late afternoon to evening
/kWh
The middle band, if your tariff has one
/kWh
/kWh
The cheapest window, often for EV charging
/kWh
What you would pay on a single-rate tariff
/kWh
Advanced / Custom Input — the tariff
Charged on both tariffs, so it does not change the comparison — shown so the totals are real.
/day
Many tariffs charge the off-peak rate all weekend.
%
%
%
Your usage
From any recent bill
kWh
On a TOU tariff this matters far more than how much you use
Advanced / Custom Input — my own split
These four should add up to 100%. The tool normalises them if they do not.
%
%
%
%
days
A load you could move
The bigger and the more predictable, the better
kW
h
nos
Advanced / Custom Input — the shift
A dishwasher moves entirely. Air conditioning usually does not.
%
The tool works out how long it takes to pay for itself.
Thinking about a battery?
Leave at 0 to skip this part
kWh
Advanced / Custom Input — the battery
You lose some of every unit you store and take back out.
%
%
One a day is 365. Fewer if you only use it in one season.
nos
Result
Put in your rates and your usage, then press “Work out my bill”.
Estimate only — verify against your own tariff and your supplier’s current rates before switching.