How the power bill estimate works
The calculator multiplies kWh by the variable cents-per-kWh rate and days by the fixed daily charge. It then adds other charges, subtracts discounts and applies the selected GST treatment.
New Zealand · Household power
Electricity bill calculator NZ
Estimate a household power bill using your kWh, variable electricity rate, fixed daily charge, billing days, discounts and GST basis.
Last reviewed: 22 August 2026
Estimated electricity bill
$231.00
for 30 days and 650 kWh
Average per day
$7.70
Effective cost per kWh
$0.36
- Variable energy charge
- $195.00
- Fixed daily charges
- $36.00
- Other charges
- $0.00
- Discounts or credits
- −$0.00
- GST included in total
- $30.13
The effective cost per kWh includes fixed charges and adjustments, so it can be higher than the variable plan rate.
Estimate only: Match every rate and adjustment to the same retailer bill. Multiple tariffs, meter readings and plan-specific charges can change the final amount.
Variable and fixed electricity charges
The energy charge changes with usage. The daily charge applies for every billing day, even when little electricity is used, so it affects the effective cost per kWh.
GST-inclusive and GST-exclusive rates
Choose the same basis used by your bill. For GST-inclusive inputs, the result identifies the GST contained in the total. For GST-exclusive inputs, it adds 15%.
Time-of-use electricity plans
Peak, off-peak, night and controlled-load usage can have different rates. Calculate each kWh block separately and combine the energy charges for a closer estimate.
Using your New Zealand electricity bill
Use a recent bill from your current retailer and plan. Look for total kWh, billing dates, variable energy rates in cents per kWh and the fixed charge in cents per day. Prices and network charges can differ across Auckland, Wellington, Christchurch, Hamilton, Dunedin and provincial electricity networks, so a national example rate is less useful than your own bill.
If the bill includes estimated meter readings, solar exports, prompt-payment credits or several meter registers, copy those items carefully. The calculator is designed for a transparent single-rate estimate rather than reproducing every retailer invoice format.
Worked electricity-bill example
For 650 kWh at 30 cents per kWh, the variable charge is $195. A 120-cent daily charge across 30 days adds $36, producing an estimated $231 GST-inclusive bill before any other charges, discounts or credits.
New Zealand electricity sources
Confirm how to read your bill with the Electricity Authority and compare currently available plans using an independent comparison service.
Frequently asked questions
How is an NZ electricity bill calculated?
A simple bill combines metered kWh multiplied by the variable cents-per-kWh rate with the fixed daily charge multiplied by billing days. Discounts, credits, other charges and GST can then change the total.
Where do I find my cents-per-kWh rate?
Check the pricing section of a recent retailer bill or your current plan details. Time-of-use plans may list separate peak, off-peak or night rates that need separate calculations.
What is the fixed daily charge?
It is a charge applied for each day in the billing period, usually shown in cents per day. It applies independently of how many kWh you use.
Should I choose GST included or excluded?
Match the basis shown on your bill or price schedule. Residential prices are commonly displayed GST-inclusive, but check the wording rather than assuming.
Can I calculate a time-of-use power plan?
Use the calculator for one rate at a time and add the energy-charge results, or use a weighted average rate. A future multi-rate comparison would be better for detailed peak and off-peak modelling.
Why will my estimate differ from the retailer bill?
Meter-reading dates, estimated readings, multiple tariffs, controlled load, levies, credits, solar exports, rounding and retailer-specific adjustments can affect the final bill.