What uses the most power in a house in NZ? Usually anything that makes heat. The answers here come from Jordan Statham, director of The Conduction Company, a registered electrician and electrical inspector whose team logs power use at the switchboard in Auckland homes.
In most New Zealand houses, anything that heats uses the most power: the hot water cylinder first, then heaters, ovens, hobs, and kettles. When The Conduction Company logs an Auckland home with a high power bill, Jordan Statham says the hot water cylinder is the culprit at least 70% of the time.
What appliances use the most power?
Anything with a heating element in it, says The Conduction Company. When the team logs a house, the biggest users are usually the hot water cylinder, ovens and hobs, and heaters running through the evening, especially in winter. Kettles, toasters, air fryers, and other kitchen appliances that heat up also draw a lot of power while they run. "Anything that has a resistive heating element within it is typically going to draw a significant amount of power," Jordan says. Basic electronics draw very little.
What runs your electric bill up the most?
The hot water cylinder, in The Conduction Company's experience. Jordan Statham puts it as the real culprit at least 70% of the time when a home is using too much power. It is also what surprises homeowners most when the team shows them the graph. "It's by far the biggest culprit for overconsumption of power within a home," he says. EECA, the government's energy efficiency agency, says water heating makes up around a third of household energy bills.
Two low-cost fixes make a real difference, Jordan says. Cutting your shower time by about half cuts how much the cylinder has to heat back up. And if the cylinder sits under the house, where it is cold and draughty, wrapping it in insulation or building an insulated box around it "makes an enormous difference to the amount of energy consumed". EECA says electric cylinders made before 2002 are not well insulated and should have a cylinder wrap, with insulation on the first metre of hot water pipe too. Never wrap a gas cylinder.
How much does a 10 minute shower cost in NZ?
About $1.60 including GST in an Auckland home, on The Conduction Company's worked example: about $1.02 of power to heat the water, and about 58 cents of water and wastewater. Jordan Statham asked for the sums to be done properly, because "there's a bunch of variable factors".
These are worked examples at average prices, not a measurement of your home. The shower runs 10 litres a minute, the average a BRANZ survey of New Zealand homes measured. Heating those 100 litres from about 17°C to 40°C takes about 2.67 kWh. The Conduction Company prices that at MBIE's average residential price for the year to March 2026, 38.29 cents per kWh including GST, plus Watercare's 2026/27 water and wastewater charges.
The same shower is about $1.78 in winter, $1.29 with an efficient 8 litre a minute head, and $2.68 with a 15 litre head in winter, all including GST. None counts the heat a cylinder loses just sitting there.
What wastes the most electricity in a house?
Faults nobody can see, in The Conduction Company's experience. Some of the biggest losses Jordan Statham has found came from things that had quietly broken, which the homeowner only saw as a bill that kept climbing.
What is the biggest overnight load The Conduction Company has measured?
About 3,000 watts, running right through the night. The logging showed straight away it was the hot water cylinder, but nothing looked wrong. The cause was a hot water leak in the subfloor, reachable only by taking off part of the decking and the fascia board. The pipes had failed and were leaking into the bare earth.
The leak did no real damage, but every litre took its heat into the ground, so the cylinder ran all night heating a steady stream of cold water. As a worked example, The Conduction Company puts eight hours at 3,000 watts at 24 kWh, about $9.19 a night including GST at MBIE's average price.
What fault has The Conduction Company found quietly burning power?
A failed underfloor heating controller in a guest bathroom. The bathroom was tucked away on another floor and kept locked, so nobody went in. The controller on the wall had failed through age, and Jordan Statham describes it as a low-quality unit. The heating ran non-stop for about five months while the homeowners tried to work out why their power bill was so high. They thought it was turned off.
On another job, a Sandringham home logged by The Conduction Company in 2025, the visit ended with two lighting sensors bypassed, so the lights went back to ordinary switching.
How do you tell a failing cylinder element or thermostat from normal use?
Often you cannot, says The Conduction Company. Sometimes the water at the taps comes out hotter than usual. But if the cylinder has a modern tempering valve (the valve that mixes hot and cold water to a set temperature), you will not notice any difference at all. Leaks are the main thing you can see, and even those hide, under the floor or out of the expansion port onto the roof. In most cases the problem is invisible unless you go looking for it. More on failed elements and thermostats is in The Conduction Company's guide to hot water recovery and cylinder faults .
Heated towel rails and underfloor heating: what do people get wrong?
They overestimate towel rails and underestimate underfloor heating, says The Conduction Company. A towel rail draws a small fraction of what a plug-in heater does. Heirloom, an Auckland maker, lists its ladder rails at 37 to 253 watts. Consumer NZ puts a plug-in heater at 2,000 to 2,400.
Jordan Statham is happy for clients to leave towel rails on for long stretches, because dry towels save on washing and drying, which use a lot more power. Just know the cost. As a worked example at MBIE's average price, a 100 watt rail left on all the time costs about $28 a month including GST, and about $4.66 including GST on a four-hour timer. BRANZ, the building research body, says "installing a timer on heated towel rails is a good idea".
Underfloor heating is the most luxurious way to heat a room, but not the cheapest. Left on all day, "it is going to cause real problems to your power bill," Jordan says. Run it on a timer or a schedule so it is only on when you are going to use the bathroom.
The team recently priced a job with underfloor heating in about five tiled areas of one house. The Conduction Company ran a full energy analysis first, to make sure it would not overload the pole fuse that feeds the house from the street. With every floor on, it would have come very close. More is on The Conduction Company's electric underfloor heating page .
How much power does each appliance use in NZ?
The Conduction Company has costed the common loads below from Consumer NZ's measured figures, at MBIE's average residential price of 38.29 cents per kWh including GST. These are worked examples at an average price, not a quote or a measurement of your home. EECA says the fridge-freezer is the third-largest use of home energy, after heating and hot water.
Plug-in heater: 2,000 to 2,400 watts, about 77 to 92 cents an hour including GST.
Heat pump: a 4.5 kW heat pump draws 1,250 to 1,800 watts, about 48 to 69 cents an hour including GST. More in The Conduction Company's guide to whether heat pumps are worth it in NZ .
Hot water cylinder: about 77 cents for every hour a 2 kW element heats, or $1.15 including GST for a 3 kW element. A bigger element heats faster, but the same water takes the same power.
Clothes dryer: about 77 cents a 3.5 kg load for a vented or condenser dryer, and 38 cents for a heat pump dryer, including GST.
Fridge-freezer: about $117 a year including GST for the average new one (306 kWh, Consumer NZ), and about $170 for a typical 15-year-old one.
Washing machine: about 10 cents for a cold wash in a front loader and 29 cents for a warm one, including GST. A warm wash in a top loader is about 48 cents.
Dishwasher and kettle: about 38 cents a load and 6 cents a boil, including GST.
How can you tell what uses the most electricity?
Start with your own data, then the switchboard, says The Conduction Company. The Electricity Authority says retailers must give you up to two years of your usage, often in half-hour blocks, in no more than five business days of asking. That shows when you use power, not what uses it.
To find what, switch circuits off one at a time and watch what changes. On a modern switchboard, with circuit breakers that look like switches, Jordan Statham says that is safe for a homeowner, though slow. Switching a breaker is operating the installation, which the Electricity (Safety) Regulations 2010 list as work that is not prescribed electrical work (Schedule 1, clause 2(e)).
Taking the cover off the switchboard is a different matter. AS/NZS 4836, the standard for safe work on low-voltage installations, says "a competent person shall determine whether it is safe" before work starts on or near one. "If you don't want all that hassle," Jordan says, an electrician from The Conduction Company can take the cover off safely and measure the current on each circuit. That finds the circuits drawing high current in about ten minutes.
For the whole picture, The Conduction Company's power logging for Auckland homes records the house for 24 to 72 hours. The electrician tests each circuit as it switches on.
Which appliance would you put a timer on first?
Underfloor heating, says The Conduction Company, because it is such a big user. Getting it to switch on only when you need it is the first win. Second is the hot water cylinder. Set it to heat in the low-rate periods on your power plan, if your retailer has them. Or set it for a few hours in the morning before you use it, and a few hours before you get home. "This can make a significant difference to your home energy costs," Jordan Statham says.
Whatever times you set, leave the thermostat alone. The Building Code's Acceptable Solution G12/AS1 says the cylinder thermostat "shall be set at a temperature of not less than 60°C to prevent the growth of Legionella bacteria".
What do older Auckland homes get wrong with hot water control?
Two things, in The Conduction Company's experience. With the Bluetooth hot water timers the team installs, set from a phone app, some people do not allow the cylinder enough time to heat.
The other is ripple control. Many people do not realise the lines company may switch their cylinder off at peak times, through a ripple relay or a pilot wire. In most of Auckland that is Vector, which says it "can temporarily turn off hot water heating to reduce the electricity demand across the network", most often on winter mornings and early evenings. Counties Energy does the same in parts of south Auckland, and controlled plans are arranged through your power retailer.
So a timer set to heat during the peak will not heat while the lines company has the cylinder off. "You really have to factor that in when setting your times," Jordan says. Most people take about a week to get the times right. The Conduction Company explains how ripple relays and pilot wires work in its guide to ripple and pilot wire hot water control in Auckland homes .
What appliances use the most electricity when turned off?
Not many, and not much, says The Conduction Company. TVs and phone chargers on standby draw very little, so Jordan Statham's advice is to leave them plugged in. "You'd be looking at cents over the night as opposed to dollars," he says. "It's really not worth the hassle of turning everything off."
Across a whole house it does add up. EECA says devices left on, even in standby mode, "can collectively add up to $200 to your yearly power bill". That is still small next to the heating loads above.
What is the one appliance you should unplug at night?
There is not really one, in Jordan Statham's view, unless it has a heating element. Unplugging is "more of an annoyance than anything", he says, and saves a few cents of standby power overnight. The exception The Conduction Company sees is salt rock lamps, which use a little power and are worth switching off when you are not using them. "However, I don't think you can turn them off for so long before they get a little yuck."
When is it the power plan, not the house, that is the problem?
Check the units on your bill before the dollars, says The Conduction Company. If the kWh have stayed flat and the bill went up, it is the price: MBIE figures show the average residential price per unit rose about 30% in the five years to March 2026.
The meter itself is rarely the problem. "Modern smart meters are quite robust units, and they've got a very low fault rate," Jordan Statham says. Rarely is not never: The Conduction Company has logged a house and found a big gap against the meter's own record. Then the company that owns the meter, the metering equipment provider, assesses it and will likely swap it, and any credit comes through your power bill.
Ask your power company first. The industry rules allow a home meter to read up to 2.5% high or low, and if the meter turns out to be fine, Consumer NZ says you might have to pay for the test.
When is paying for power logging worth it, and when is it not?
When your power bill is much higher than it should be and you cannot work out why, says The Conduction Company. An electrician finds out exactly what is going on, and the team can usually automate or fix it quickly. Jordan Statham says the same goes for commercial property owners with a big power draw, where a few basic automations often make big savings.
We quote on facts, not guesses
The estimates below are for standard power logging of a home. The Conduction Company confirms final pricing after a property assessment.
The Conduction Company's power logging for homes starts from $590 including GST. That includes the logging, the usage graphs, and a report with recommendations. Any fix the report recommends is quoted separately. What you save depends on what the logging finds, so The Conduction Company does not promise a figure before it has measured.
It is not worth paying for when the units on your bill have not changed. Then the price has risen, not your usage, and comparing plans on Powerswitch may help more than any electrician, The Conduction Company says.
In short
Anything that makes heat uses the most power in a New Zealand house, and the hot water cylinder is usually first. Based on what The Conduction Company finds when it logs Auckland homes, Jordan Statham puts the cylinder as the culprit at least 70% of the time. The worst waste comes from faults nobody can see, like a hidden hot water leak or a failed underfloor heating controller. Standby power from TVs and chargers costs cents a night, so it is not worth chasing. To find your own biggest user, ask your power company for your usage data, switch circuits off one at a time on a modern switchboard, or have the whole house logged.
Frequently asked questions
What appliance is the biggest energy waster?
Usually the hot water cylinder, and worst of all a cylinder heating water that is leaking away, The Conduction Company finds. On one Auckland job a hidden hot water leak under the floor kept a cylinder drawing about 3,000 watts all night. A failed underfloor heating controller that ran for about five months is another.
Does leaving a TV plugged in use electricity?
A little. Consumer NZ found some TVs, games consoles, and microwaves draw 2 to 5 watts on standby. At MBIE's average price, 3 watts all year is about $10 including GST. Jordan Statham of The Conduction Company says it is cents a night, so leave the TV plugged in.
How much does it cost to have a TV on for 4 hours?
About 8 cents for a 40-inch LED TV and about 20 cents for a 70-inch OLED, including GST, on The Conduction Company's worked example using Consumer NZ's wattages and MBIE's average price. Eight hours doubles it, to about 15 and 40 cents.
Does leaving a kettle plugged in use electricity?
Next to none if it is switched off at its own switch. Consumer NZ's rule of thumb is that "the dumber an appliance is, the less energy it will consume while on standby", so a kettle with a display or keep-warm setting may draw a little. The Conduction Company does not think it is worth unplugging.
What are the worst appliances to leave on standby?
Consumer NZ found some TVs, home theatre systems, games consoles, and microwaves draw 2 to 5 watts on standby. That is still cents a night, says The Conduction Company. Anything with a heating element, like a salt rock lamp, is the one to switch off.
What appliances should be unplugged when not in use to save electricity?
Very few. Jordan Statham of The Conduction Company says unplugging most things saves a few cents a night. The exception is anything with a heating element, such as a salt rock lamp. A typical salt lamp bulb is 15 watts, about $50 a year including GST if it is never switched off.
What appliances should you never leave plugged in?
For saving power, none that The Conduction Company would single out, because standby costs cents. Switch off the things that heat when you are not using them, like a salt rock lamp, or underfloor heating in a room nobody is using.
Is it cheaper to boil a kettle or a pan?
The kettle. Consumer NZ's tests found an induction cooktop uses around 20% more energy than an electric kettle to boil water, and a ceramic cooktop uses more than induction. At about 6 cents a boil including GST, The Conduction Company's worked example, the kettle is cheap either way.
Do washing machines use a lot of electricity?
Not on a cold wash. Using Consumer NZ's figures, The Conduction Company works a front loader out at about 10 cents a cold wash and 29 cents a warm one, including GST. A warm wash in a top loader is about 48 cents, and the clothes dryer, at about 77 cents a load, uses more than the washer.
How much kWh does a house use per day in NZ?
About 18.7 kWh a day. MBIE puts the average New Zealand household at 6,836 kWh a year from the grid in the year to March 2026, and the Electricity Authority has Auckland homes at 6,822 kWh in 2025. The Conduction Company's logging shows how your own day splits up.
