Time-of-use meters in practice
Short answer. A TOU meter keeps two accumulators — peak and off-peak — and the bill prices them at different rates. Whether it pays depends entirely on the share of your consumption that is genuinely shiftable: water heating, laundry, ironing and pumping are, while lighting and evening cooling are not.
Who this is for: Consumers already on TOU billing who want to read both registers, and those considering it who need an honest answer on whether it pays.
Reading both registers
The screens are coded 1.8.1 and 1.8.2 on most meters, corresponding to the two rate periods. Their sum is the total on 1.8.0.
Record both on the same date each month. The ratio between them is the number that determines whether you are winning or losing on this tariff, and it is not printed anywhere except your own notes.
Working out whether it pays, before switching
List your loads and mark each as shiftable or not. A geyser, a washing machine, an iron and a water pump are shiftable. A refrigerator runs regardless. Lighting and evening air conditioning are precisely peak-period loads and cannot move.
Estimate the units in each group. If more than half your consumption is fixed in the peak window, TOU will cost you more, because the peak rate is applied to it.
The households that gain most are those with electric water heating, significant pumping, and a habit of running laundry during the day.
Pre-cooling, the one trick for air conditioning
Cooling cannot be moved out of the evening, but part of it can be brought forward. Running the air conditioner harder before the peak window opens and then raising the setpoint during it shifts some of the energy into the cheaper period.
How much this is worth depends on the building. A concrete house with an uninsulated roof loses the stored coolth quickly; a better-insulated one holds it for an hour or two and the saving is real.
Where the window actually falls
It is a notified evening window that shifts between summer and winter schedules, and it is printed on the bill. Working from a remembered figure is how people end up running a geyser inside the expensive hours.
Check the schedule printed on your own bill at the start of each season rather than assuming last year's hours still apply.
Frequently asked questions
How do I know if I am on a TOU tariff?
The bill shows two sets of readings and two energy lines. A single reading pair and a single energy line means you are billed on the ordinary schedule regardless of what kind of meter is on the wall.
Can I switch back if TOU turns out to be worse?
Category changes are applications like any other, and they are considered on their merits. It is far better to do the arithmetic before switching than to argue for a reversal after a bad summer.
Related meter guides
Go further
All 10 guides are listed in the meter guides index. To check the reading against your actual bill, open the official duplicate.