How business time-of-use windows change your annual cost

A time-of-use tariff charges a different rate for the same kilowatt hour depending on when you used it, so two businesses that consume exactly the same amount across a year can pay materially different amounts for it. What decides the gap is the share of your usage that falls inside the peak window, and that share is a fact about how you trade rather than a number you can read off a rate table.

This page is about what the windows do to the total at the bottom of your bill. It is not a list of every network's windows, because a list cannot tell you what yours costs you.

What is a time-of-use window on a business electricity bill?

A time-of-use window is a defined block of hours, days and sometimes months within which a single usage rate applies, so that the same kilowatt hour is priced differently depending on when it was drawn.

Most business tariffs run two or three of them. Peak is the expensive window, set over the hours the network is under most pressure. Off-peak is the cheap window, usually overnight and at weekends. Shoulder, where a tariff has one, sits between the two in both time and price. The rate for each is printed on your bill next to the kilowatt hours you used inside it, which is the only place your own split is recorded.

Who sets the peak window, my retailer or my network?

Your network, through the tariff assigned to your site, and in most cases your retailer has no ability to change it. The distributor sets the structure and the hours; the retailer prices a plan that sits on top of it and adds its own margin.

This is the same division of labour that governs demand charges, and it has the same consequence: shopping for a retailer does not move your windows. It moves what you pay for the electricity inside them. Where the regulator publishes a default tariff for your jurisdiction, the windows in that default are set by the regulator rather than by either party.

Do peak windows differ between states and networks?

Substantially, and the difference is larger than most businesses expect. Two published examples make the point without either of them being your answer.

In Victoria, the two-period time-of-use tariff for small business customers in the Essential Services Commission's Victorian Default Offer determination for 2026 to 2027 defines peak as 9am to 9pm on weekdays, with off-peak covering all other times. That is a twelve hour peak across the entire working day.

In regional Queensland, the small business time-of-use tariff in the Queensland Competition Authority's notified prices for the same year puts peak at 5pm to 8pm on weekdays, with a separate daytime rate from 11am to 1pm and a third rate for everything else. That is a three hour peak, sitting after most shops have closed.

Same country, same year, both set by a regulator, and a business would organise its day completely differently under one than the other. Within a state it varies again, because each distributor publishes several tariff codes and your site sits on one of them. That is why this page does not carry the full list: a list long enough to be correct is too long to find yourself in, and the tariff code printed on your own bill answers the question in one line.

How much difference does the peak share make to an annual bill?

Enough to change which plan is cheapest, which is easier to see with round invented numbers than with real ones. The rates below are made up to keep the arithmetic legible. They are not market rates and nothing on this site prices anything from them.

Take a plan charging 40 cents a kilowatt hour in peak and 20 cents outside it, and a business using 30,000 kilowatt hours a year. Hold everything else equal so the windows are the only variable.

• A business with 60 per cent of its usage in peak pays 18,000 kilowatt hours at 40 cents plus 12,000 at 20 cents. That is $7,200 plus $2,400, or $9,600.
• A business with 25 per cent of its usage in peak pays 7,500 kilowatt hours at 40 cents plus 22,500 at 20 cents. That is $3,000 plus $4,500, or $7,500.

Identical annual consumption, $2,100 apart, purely on when the business trades. Now put a flat rate of 27 cents beside them. The same 30,000 kilowatt hours costs $8,100 flat, whatever the hour. The first business is better off on the flat rate by $1,500. The second is better off on time-of-use by $600.

That is the whole argument on this page. The same two plans reverse their order depending on a number that appears nowhere in either plan's rates, because it is a fact about the business rather than about the plan.

Is a time-of-use plan cheaper for my business than a flat rate?

It depends entirely on your load shape, and it cannot be answered from the rates alone. A business whose trade happens outside the peak window does well on time-of-use. A business whose trade happens inside it does badly, and would often be better on a flat rate even at a higher headline number.

Which is why a sharp peak rate is not evidence of a cheap plan, and why the cheapest rate and the cheapest bill are different questions. A plan quoting the lowest off-peak rate in the market is irrelevant to a business that closes at five.

Can I move my usage out of the peak window?

Some businesses can and some genuinely cannot, and it is worth being honest about which one you are before anybody sells you a solution.

What moves reasonably well: pre-cooling and pre-heating, batch production, dishwashing, laundry, charging, pumping, and cleaning. What does not move is trade itself. A café's peak is peak because that is when people want coffee, and a plan that requires it to stop serving at three is not a plan.

Where the load cannot move, the answer is not behavioural. It is picking the plan that prices your actual shape most cheaply, which is arithmetic rather than effort.

What is the difference between a time-of-use window and a demand window?

A time-of-use window prices the quantity of electricity you used inside it, in kilowatt hours. A demand window measures the highest rate at which you drew electricity inside it, in kilowatts, and prices that peak instead of the quantity.

The two often overlap in the same hours on the same bill, which is why they get confused, but they respond to different things. Using less across the afternoon lowers a time-of-use charge. Only lowering your worst single interval lowers a demand charge. If your bill carries a line priced in kW or kVA, demand charges explained is the page for that line, and the two need reading together rather than one at a time.

How do I find my own peak and off-peak split?

It is already printed on your bill. A time-of-use bill itemises the kilowatt hours in each window separately, because it has to in order to charge different rates for them, so your split is recorded on every bill you have ever been sent.

That is the number the comparison needs, and it is the reason we ask for a bill rather than a postcode. Upload your business electricity bill and the engine reads the usage in each window along with the rates and the tariff, prices the published plans available at your site against your own split, and ranks them by projected annual cost with the arithmetic shown. Where a plan's windows are defined differently from the ones your bill recorded, the figure is presented as an approximation, because that is what it is. Where a plan cannot be priced from what your bill prints, it is flagged rather than given a favourable guess.

Related reading

For the full set of tariff structures and how each one charges, electricity tariffs explained. To find the windows and rates on the page in front of you, how to read a business electricity bill goes line by line. And to see what your site would pay across the published plans, start at business electricity plans.