The 40-second answer
To work out what any appliance costs to run in New Zealand, use (watts ÷ 1000) × hours used × your unit rate. The watts are on the appliance label; dividing by 1,000 gives kilowatts, times the hours gives kilowatt-hours (kWh), the unit your bill is priced in. At today's NZ average of about 34.4 c/kWh, a 1,500 W heat pump run 6 hours costs roughly $3.10 a day. Your full bill is that usage cost plus a fixed daily charge.
Calculator uses the formula (watts ÷ 1000) × hours × rate. Unit rate is pre-filled live (34.40 c/kWh). The appliance running-cost table below lists the same figures, so the page works without JavaScript.
Key takeaways
- The formula: (watts ÷ 1000) × hours × unit rate = cost. That is all there is to it.
- 1 kWh = a 1,000 W appliance running one hour. The average NZ home uses ~7,100 kWh/year (~19 kWh/day).
- Hot water and heating dominate. Hot water alone is often ~30% of the bill, that is where to focus, not phone chargers.
- Wattage is not everything: a kettle draws 2,400 W but runs minutes; a 150 W fridge runs all year and costs more.
- You also pay a daily fixed charge ($1.80–$3.00/day) regardless of usage, so cutting kWh only changes part of the bill.
How to read your power usage in kWh
Electricity is sold in kilowatt-hours (kWh), the "units" on your bill. One kWh is what a 1,000-watt appliance uses in one hour. A 2,000 W heater run for 30 minutes uses 1 kWh; a 100 W TV left on for 10 hours also uses 1 kWh. To find any appliance's usage yourself:
The two formulas you need
Energy used: watts ÷ 1000 × hours = kWh
Cost to run: kWh × unit rate (c/kWh) ÷ 100 = $
Worked example: a 3,000 W hot-water cylinder heating for 3 hours a day uses 3 ÷ 1000 × 3 = 9 kWh/day. At 34.4 c/kWh that is 9 × 34.4 ÷ 100 = $3.10 a day, or about $1,130 a year, before the daily fixed charge.
Your bill shows total kWh for the period, and most online accounts plot daily usage. Comparing that graph to your appliance estimates is how you find where the money goes. Then add the daily fixed charge ($1.80–$3.00/day depending on plan and region) to get your full bill, see how that fits the wider picture in our NZ electricity prices breakdown.
Appliance running costs in NZ (at 34.4 c/kWh)
These are the same figures the calculator produces, at the live NZ average rate, for typical daily use. Your real cost depends on your appliance, settings and rate.
| Appliance | Power | Typical use | Per day | Per year |
|---|---|---|---|---|
| Heat pump (heating) | 1,500 W | 6 h/day | $3.10 | $1,130 |
| Plug-in electric heater | 2,000 W | 5 h/day | $3.44 | $1,256 |
| Hot water cylinder | 3,000 W | 3 h/day | $3.10 | $1,130 |
| EV home charging | 7,000 W | 2 h/day | $4.82 | $1,758 |
| Clothes dryer | 2,500 W | 0.5 h/day | $0.43 | $157 |
| Electric oven | 2,400 W | 0.5 h/day | $0.41 | $151 |
| Dishwasher | 1,200 W | 1 h/day | $0.41 | $151 |
| Washing machine | 500 W | 0.75 h/day | $0.13 | $47 |
| Fridge-freezer | 150 W | 8 h/day | $0.41 | $151 |
| Heated towel rail | 80 W | 24 h/day | $0.66 | $241 |
| TV (LED, 55") | 100 W | 4 h/day | $0.14 | $50 |
| Electric kettle | 2,400 W | 0.2 h/day | $0.17 | $60 |
A clear pattern emerges: the dearest items to run are not the highest-wattage ones, they are the ones that run the longest. The kettle's 2,400 W barely registers because it is on for minutes; the 150 W fridge and the always-on towel rail cost more because they never stop.
The running cost of a heat pump (and why it still wins)
Heating is the question we get asked most, so it is worth its own look. A common single-room heat pump draws about 1,500 W while running. At 34.4 c/kWh that is roughly $0.52 per hour. Run it 6 hours on a cold evening and that is about $3.10 a day; lean on it all winter and it climbs into the hundreds.
Yet a heat pump is still the cheapest electric heating, and the reason is efficiency. A plug-in heater turns one unit of electricity into one unit of heat. A heat pump moves heat rather than making it, delivering about 3 to 4 units of heat for every unit of electricity. So a 1,500 W heat pump warms a room like a 4,500–6,000 W heater would, at a third of the running cost. The trap is the cheap plug-in heater in the table above: same comfort, triple the bill.
To cut heating cost without losing warmth: set the heat pump to a steady 18–20 °C rather than blasting it on arrival, heat only the rooms you use, and run it harder in the cheaper off-peak window where your plan offers one. Insulation and curtains do the rest, see Warmer Kiwi Homes for free or subsidised insulation.
What is an average bill for my home size?
Working bottom-up from appliances is precise but slow. For a quick sense-check, here is the rough annual usage and cost by household size, at the live average rate plus a typical $2.40/day fixed charge.
| Household | Annual kWh | Est. cost/year | Est. cost/month |
|---|---|---|---|
| 1 person / flat | 4,000 | $2,252 | $188 |
| 2 people | 6,000 | $2,940 | $245 |
| 3–4 people | 8,000 | $3,628 | $302 |
| 5+ / large home | 11,000 | $4,660 | $388 |
Compare your own bill to your row. Well above it? You are either a heavy user (electric heating, EV, pool pump) or on a dear plan, worth checking with our average electricity bill guide. For the full method to lower the rate rather than just the usage, see how to compare electricity prices.
The two numbers that decide your bill
Most energy-saving advice fixates on switching things off: standby power, phone chargers, the "vampire" loads. They are real, but small. The numbers above show why: the savings live in how long your biggest loads run (hot water, heating, EV) and in the unit rate you pay for them, not in the trickle from a charger.
Here is the part that surprises people. You can cut your usage hard and still see only part of the saving, because a chunk of your bill is the daily fixed charge you pay whether you use 1 kWh or 100. With the low-user cap now $1.80/day and standard charges up to ~$3.00/day, that is $657–$1,095 a year locked in before any power flows. So the most powerful lever is usually not using less, it is pairing sensible usage with the right plan and rate. Knowing your kWh, as this page teaches, is what lets you do both: trim the loads that matter, then take your real usage shopping for a cheaper rate.
The Selectra expert's take
Cornelia Zavoianu, energy market analyst
"When people calculate appliance costs for the first time, the shock is never the heater they expected, it is the small always-on stuff. A heated towel rail left on 24/7, an old second fridge in the garage, a hot-water cylinder with no timer. Those quietly cost more in a year than the dryer they worry about."
"Use the wattage maths to find your top three loads, then attack them in order: a hot-water timer, a heat pump instead of plug-in heaters, and EV or laundry shifted to off-peak. But remember the fixed daily charge, $657 to over $1,000 a year, does not budge no matter how careful you are. That is why calculating your usage and then comparing your rate beats either move alone."
This suits you if you want to target savings instead of guessing. It becomes a risk when you obsess over tiny loads and ignore the rate. Figures here use typical wattages and the live average rate; your appliance and bill will differ, always check your own."
Frequently asked questions
Use this formula: (watts ÷ 1000) × hours used × unit rate. First find the appliance's wattage (on its label or manual), divide by 1,000 to get kilowatts, multiply by the hours you run it to get kilowatt-hours (kWh), then multiply by your unit rate. At the current NZ average of about 34.4 c/kWh, a 1,500 W heat pump run 6 hours a day costs roughly $3.10 a day, or about $1,130 a year.
A typical 1,500 W (heating output ~6 kW) heat pump uses about 1.5 kWh per hour of run time. At the NZ average rate of about 34.4 c/kWh, that is roughly $0.52 per hour. Run 6 hours a day through winter, that is about $3.10 a day. A heat pump is still the cheapest electric heating because it moves about 3–4 units of heat for every unit of electricity, far more efficient than a plug-in heater of the same wattage.
One kilowatt-hour (kWh) is a 1,000-watt appliance running for one hour, the "unit" your bill is priced in. Your bill shows total kWh used in the period, and your online account usually shows a daily graph. To estimate any appliance yourself: watts ÷ 1,000 × hours = kWh. A 2,000 W heater for 3 hours = 6 kWh. Most NZ homes use around 7,100 kWh a year, or roughly 19 kWh a day.
Three things dominate: hot water (often ~30% of the bill), space heating (heat pumps and heaters, biggest in winter), and appliances and lighting combined. Hot water and heating are where the real savings are, through timers, off-peak windows, insulation and efficient heat pumps, not by unplugging phone chargers. The largest "hidden" loads are always-on items: the hot-water cylinder, fridge-freezer and any heated towel rails left on 24/7.
The average New Zealand household pays an all-in effective rate of about 34.40 c/kWh (incl. GST) once the daily charge is spread across usage. Pure unit rates on standard plans typically sit between 25 and 30 c/kWh. The calculator on this page uses the live average; your own rate is on your bill and may be higher or lower depending on your region, plan and meter.
