In New Zealand a hot water cylinder should store water at 60°C or higher, so it kills Legionella bacteria. Water delivered to showers, baths and basins must then be cooled to a safe temperature, which is 50°C for most new bathroom fixtures installed since 2 November 2024. A tempering valve does that mixing. Turning the cylinder down below 60°C to save power is not safe, and the saving is small.
Cylinder temperature is one of those settings most people never think about until something goes wrong: a scalding tap, a shower that never gets properly hot, or a power bill that looks too high. It is also an area full of advice that is either out of date or unsafe.
This guide sets out the two temperature rules that matter, how long a cylinder takes to heat, the truth about switching it off to save power, and what you can and cannot safely do yourself.
What temperature should a hot water cylinder be set at in NZ?
Set the stored water to at least 60°C. Building Performance, the government building regulator, says the answer to the conflict between bacteria and scalding is to store hot water at a minimum of 60°C and deliver it to baths, showers, basins and bidets at no more than 50°C.
The 50°C limit applies to new personal hygiene fixtures installed on or after 2 November 2024 under the acceptable solutions. It is not retrospective, so older bathrooms set to the previous 55°C limit are not automatically non-compliant. Kitchens and laundries are allowed hotter water. BRANZ's Level guide says hot water at kitchen sinks and laundries is generally around 55°C to 65°C.
The device that makes both rules work at once is a tempering valve on the bathroom supply. If your bathroom taps run far hotter than the kitchen, or a new cylinder has made the shower dangerously hot, have the tempering valve checked.
| Where | Temperature | Why |
|---|---|---|
| Inside the cylinder | 60°C or higher, at least once a day | Controls Legionella |
| Bathroom fixtures installed from 2 November 2024 | 50°C maximum | Scald protection |
| Older bathroom fixtures | 55°C under the earlier limit | Not retrospective |
| Kitchen sink and laundry | Generally around 55°C to 65°C | Hotter water for cleaning |
How long does a hot water cylinder take to heat up?
A full heat from cold takes roughly two to five hours for a typical electric cylinder, depending on its size and element. Recovering after a couple of showers is much quicker, because only the cold water that has flowed in needs heating.
The table below shows approximate full heat times for a 3 kW element raising water from about 15°C to 60°C. These are physics based estimates, not manufacturer figures. Gas storage cylinders recover faster, and heat pump water heaters are usually slower but use far less electricity.
| Cylinder size | Energy to heat from cold | Approximate time at 3 kW |
|---|---|---|
| 135 litres | About 7 kWh | About 2.5 hours |
| 180 litres | About 9.4 kWh | About 3 hours |
| 250 litres | About 13 kWh | About 4.5 hours |
| 300 litres | About 15.7 kWh | About 5 hours |
Does turning off the hot water cylinder save power?
Only when you are away for several days. Switching off overnight or during the day saves very little, because the water you use still has to be heated, and it creates a real risk that the cylinder never reaches 60°C.
A cylinder loses some heat through its walls all the time, known as standing loss, and that is the only power a daily switch off can save. For a week away, turning it off is sensible. When you get back, switch it on and let it heat fully before anyone showers, so the whole tank has been above 60°C. Holiday homes are the classic case. If you own a bach in a beach town like Orewa, which grew through its 1964 to 1975 building boom, switching the cylinder off when you lock up is an easy saving. Cheeky's Plumbers has plumbers covering Orewa who can fit a timer or check the cylinder if it is slow to come back up to temperature.
Water too hot or not hot enough?
Cheeky's Plumbers checks your cylinder and tempering valve, sets them to the rules and tells you the price before any part is replaced.
How do I reset my hot water cylinder?
Check the simple things first: the cylinder's circuit breaker or fuse at the switchboard, and whether your power plan uses a controlled tariff that switches the cylinder off at peak times. Many no hot water calls are a tripped breaker or a controlled supply that has not switched back on yet.
Electric cylinders also have an over temperature cut out on the thermostat, with a small reset button behind the element cover. That cover hides live 230 volt wiring, so do not remove it yourself. A cut out that trips once may be a one off, but one that keeps tripping means a faulty thermostat or element. That is a hot water repair job, with any electrical work handled by a registered electrician where it is required.
How do I drain my hot water cylinder?
Turn the power off first, then the cold supply, open a hot tap to let air in, and drain through the drain valve or outlet with a hose to a safe place. The order matters. An electric element switched on in an empty cylinder burns out in seconds.
In practice, draining is rarely something a homeowner needs to do. Mains pressure cylinders have valves that need correct handling, the water inside is hot enough to burn, and older drain valves often will not reseal once opened. Draining is usually done as part of a hot water service or replacement, so leave it to the plumber doing that work.
How much power does a hot water cylinder use?
Quite a lot. EECA says heating water makes up about 30% of the average New Zealand household's energy use, making it one of the biggest items on the power bill after space heating.
Most of that energy goes into the water you actually use. As a rule of thumb, heating each litre from cold to 60°C takes about 0.05 kWh, so a household using 200 litres of hot water a day needs around 10 kWh daily before standing losses. The best savings come from using less hot water, with shorter showers and efficient shower heads, insulating the first metre of pipe from the cylinder, and fixing dripping hot taps or valves. Turning the thermostat below 60°C is not a safe way to save.
When should you get your cylinder temperature checked?
Get it checked if the hot taps are scalding, the water is never properly hot, the relief valve drips constantly, or the cylinder is old and has never been serviced. A plumber can measure the stored and delivered temperatures and adjust or replace the parts that control them.
The rules differ with the age of the bathroom. In newer subdivisions such as Takanini, homes with bathroom fixtures installed since November 2024 should be delivering no more than 50°C. In Remuera, where many homes are Edwardian or mid 20th century, older cylinders and tempering valves may have drifted over the years. Cheeky's Plumbers checks valve settings and temperatures as part of a hot water service, and arranges hot water repairs in Remuera and across Auckland when a part has failed. You can book online at a time that suits.
Frequently Asked Questions
Can I turn my cylinder thermostat down to 55°C to save money?
No. Stored water needs to reach at least 60°C to control Legionella, and the energy saved by running a few degrees cooler is small. If the taps are too hot, the safe fix is a correctly set tempering valve on the bathroom supply, not a lower thermostat.
Why is my hot water hotter than usual?
A thermostat that has drifted or failed, or a tempering valve that has stuck, can both send much hotter water to the taps. Treat sudden scalding water as urgent, especially with children or older people in the house, and get a plumber to test the cylinder and valve.
Why is my hot water lukewarm?
Common causes are a failed lower element, a thermostat set or stuck too low, a controlled tariff switching the cylinder off, or a tempering valve out of adjustment. A cylinder that is simply too small for the household can also run lukewarm by evening.
What is Legionella and why does 60°C matter?
Legionella is a bacterium that can grow in warm stored water and cause a serious lung infection when breathed in as fine droplets, such as shower spray. Heating stored water to 60°C or more at least once a day keeps it under control, which is why the Building Code guidance sets that minimum.
Should a gas cylinder be set to the same temperature?
Yes. The storage and delivery rules are the same whatever heats the water. Gas storage heaters and continuous flow units have their own controls, and continuous flow units are often set to deliver directly at a safe temperature. Your gasfitter should confirm the settings for your model.
Does a heat pump water heater reach 60°C?
Most are designed to, either on their own or with a backup element that boosts the tank on a schedule. If you have one, check the maker's settings for the Legionella cycle and make sure it has not been switched off to save power.
Our Services
Hot Water Servicing
A quick service checks your valves, element and pressure so your cylinder lasts longer and stays safe.
View serviceTempering Valves
Tempering valves and thermostatic mixing valves tested, adjusted and replaced, so bathroom taps stay below scalding point while your cylinder stays hot enough to control Legionella.
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