A bill is not a price someone set for you. It is a receipt for habits you have already finished having.
There is one equation behind the whole house, and it is short enough to remember:
watts × hours = the unit. 1,000 watts for one hour is 1 kilowatt-hour, and at the current regulated tariff that is
31.16 cents (
SP Group tariff, 1 Oct – 31 Dec 2026). So a 1,000 W appliance costs 31 cents an hour — and a 100 W fan for ten hours is the same 1,000 watt-hours, so it costs exactly the same 31 cents. That is the first surprise. It is not the speed of the machine that costs money, it is watts multiplied by time. A 1,500 W aircon for one hour is about 47 cents; the same hour every night for a month is about
$14. A 2,000 W kettle boiling for three minutes is about 3 cents, and the guilt was always in the wrong place.
The second surprise is that the rate is not one number either. The 28.59 cents you pay before GST is already four charges added together: energy costs 22.18c, paid to the companies that generate the power; network costs 6.10c, paid to move it to your block; a market support services fee of 0.23c for billing and meter reading; and a market admin fee of 0.08c. Add 9% GST and you land on the 31.16 cents on the bill. Every line is somebody’s actual job, which is a useful thing to know before you shout at a number.
Water is a bigger stack. PUB lists
three components in the monthly bill: the water tariff, the water conservation tax, and the waterborne tax. One of those has nothing to do with the clean water that reaches your tap — the waterborne tax pays to collect the used water, carry it away and treat it before it goes back to the sea or back into NEWater. The tariff alone is
$1.56 per cubic metre (1,000 litres) with GST, and the other two sit on top of it, so a 10-litre bucket is about 1.6 cents of water and a good deal more once everything wrapped around it is counted.
Now the part that matters more than the arithmetic. Most families have never guessed what one month of home costs, and the gap is almost never the price — it is the units. You cannot cut a number you have never guessed, and on the day the bill jumps, guessing first is what turns a nasty surprise into a subtraction you can do. Nobody in this house needs to become an accountant. They need to know that every appliance has a label with watts on it, and every bill has a line with units on it, and those two numbers are the whole game.
So do it properly tonight: one guess, one real bill, one appliance. Find the label, do the multiplication, and decide if that thing deserves the hours you give it. That is a whole financial education, and it fits in five minutes.