Understanding your power bill

Most power bills in New Zealand look complicated because they show two businesses' charges in one document. Once you know which lines belong to which, the rest is arithmetic.

The two kinds of charge

A daily charge. A fixed number of cents for every day you were connected. You pay it whether the house was full or empty. On a 30-day bill it is the same on every bill you will ever get, give or take the number of days in the month.

A usage charge. Cents per kilowatt hour (kWh), multiplied by how much you used. A kWh is one unit: a 1,000-watt heater running for an hour.

Add them together, and that is the bill. Everything else on the page is either a breakdown of those two, a discount applied to them, or GST.

Why there is more than one usage rate

If your bill shows an "anytime" or "uncontrolled" rate and a second, cheaper "controlled" rate, your property has more than one metering register. The usual arrangement is that hot water sits on a controlled circuit which the lines company can interrupt for short periods at peak demand. You almost never notice — a well-insulated cylinder holds heat for hours — and the electricity going through that circuit is charged less.

Some properties also have a night rate, or an inclusive rate that bundles everything into one number. Which you have is a property of the wiring and the meter, not something you choose when you sign up. Our guide to meter types goes through each configuration.

Where the money actually goes

This is the part most bills do not show, and it changes how you think about switching.

Roughly speaking, a New Zealand power bill splits into the charge from the lines company that owns the poles and wires in your area, and the charge from the retailer that buys electricity and bills you. You choose the second. You do not choose the first. It comes with the address.

MBIE publishes the split for each of the 42 towns it surveys, and the difference between towns is almost entirely lines. Nationally the average sits at 42.04c per kWh including GST as at May 2026, which for a household using 8,000 kWh a year is about $3,363. In Balclutha that same household pays more than in Wellington City, and no amount of switching closes the gap.

What switching can move is the retail half. That is still worth doing. It is most of the difference between a good deal and a bad one at the same address.

The discount line

A "prompt payment discount" is a percentage off if you pay by the due date. It is worth having, and it is worth reading carefully: the rate quoted in the advertising is usually the discounted one, so missing a due date costs more than it looks. Some retailers have dropped the mechanism entirely in favour of a single lower rate, which makes comparison easier and is not automatically cheaper.

Estimated readings

If your bill says "estimated", nobody read the meter: the retailer projected your usage from history. It is not a made-up number, but it will be corrected at the next actual reading, and a run of low estimates followed by one real reading is the classic cause of a shock bill. If you have an older meter, submitting your own reading is usually possible and takes a minute.

The checks worth doing once a year

• Compare this bill to the same month last year, not to last month. Power use is seasonal.
• Check the total kWh for the year, because you need it to compare plans properly.
• Check you are on the right user type. If you use well under 8,000 kWh a year you may be on the wrong plan for your usage, and that is changing in 2027 anyway.
• Check whether the plan you signed up to still exists at the price you signed up at.