Reducing the cost of your shower before peak power hours

When people hear "off-peak", they tend to picture doing things late at night. For showering, that's only half the picture. On Night Saver, the lower-rate window runs until 7am, so an early morning shower can land in the same lower-rate hours as a late evening one, before most of the country is up and the morning peak gets going.

This guide is written for homes with an electric hot water cylinder, which is the most common set-up in New Zealand. It looks at what heating that water costs, why the shower is such a big part of it, and how the timing of your shower fits in. If your water is heated by gas, or by a hot water heat pump, the costs work differently and we've noted that below.

Night Saver offers lower rates from 9pm to 7am compared to day rates on the same plan. Any savings depend on your usage and how much of it you shift into those hours. Ts&Cs and eligibility criteria apply.

Hot water is a big part of your power bill

Water heating makes up around a third of household energy bills, according to EECA. In most homes, the shower is the single biggest user of that hot water. Our bathroom guide covers the everyday habits that bring hot water use down. Here, we're focused on the shower itself and when it happens.

How your cylinder actually works

An electric cylinder holds a tank of water and keeps it hot, ready for when you need it. EECA advises that water should be at least 60°C at the cylinder, to prevent the growth of legionella bacteria, and no more than 55°C at the tap so nobody gets burnt.

You don't shower in 60°C water. The hot water from the cylinder is mixed with cold on its way to the shower head, giving a comfortable shower temperature of around 40°C. So a shower running at 9 litres a minute is drawing roughly 5 litres a minute from the cylinder, with the other 4 litres made up of cold.

The electricity is used when the cylinder reheats the cold water that flows in to replace what you've drawn off. That's why the cost of a shower depends on how much hot water leaves the cylinder, not on how hot the cylinder is set.

What a shower uses

Taking mains water at around 15°C up to shower temperature works out at roughly 0.029 kWh for every litre that comes out of the shower head. How much that adds up to depends on two things: how long the shower runs and how fast the water flows.

Shower length

At 9 L/min: energy

At 9 L/min: cost at 42c

At 9 L/min: hot water drawn from cylinder

At 12 L/min: energy

At 12 L/min: cost at 42c

5 minutes

1.3 kWh

55c

25 L

1.7 kWh

73c

8 minutes

2.1 kWh

88c

40 L

2.8 kWh

$1.17

10 minutes

2.6 kWh

$1.10

50 L

3.5 kWh

$1.47

15 minutes

3.9 kWh

$1.65

75 L

5.2 kWh

$2.20

Worked out from the water that comes out of the shower head, heated from around 15°C to about 40°C, with cylinder draw shown at 60°C. These figures cover the energy to heat the water only, for a home with an electric hot water cylinder. They don't include heat lost from the cylinder and pipes, so real-world use will be a little higher. These figures are indicative estimates, not a bill guarantee. Costs use the national average residential price of 42.1c per kWh from MBIE's Quarterly Survey of Domestic Electricity Prices (15 August 2026), rounded to 42c. Your own rate will depend on your plan, network and region, and actual energy use varies by model, settings and how you use it.

An 8-minute shower at 9 litres a minute, every day, uses around 760 kWh a year. For a household of four, that's over 3,000 kWh.

Flow matters as much as time

EECA suggests a simple bucket test. If your shower fills a 10-litre bucket in under a minute, it's using more water than it needs to. It estimates a shower head that cuts the flow by just 1 litre a minute could save a household of four around $80 a year.

When does a shower actually use power?

The cylinder does the heating

Your shower uses hot water that's already stored in the cylinder. The electricity is used when the cylinder's element switches on to heat the cold water that flows in to replace it. On most electric cylinders, that starts during your shower and carries on for a while afterwards, until the tank is back up to temperature.

What that means for timing

This is why an early shower works well on a time of use plan. Shower at 6am and most of the reheating is likely to be done before 7am. Shower at 6.55am and more of it will fall into the day rate. The same goes at night, where a shower after 9pm keeps the reheat inside the lower-rate hours.

Shower time

Where most of the reheating is likely to fall on Night Saver

Before 6am

Lower-rate hours

6am to 6.45am

Mostly lower-rate hours, with some reheating likely to run past 7am

6.45am to 9pm

Mostly day rate

After 9pm

Lower-rate hours

The exact timing depends on your cylinder's size and element, how much hot water gets used and how your hot water is set up, so treat this as a guide rather than a rule.

Your set-up makes a difference

  • Controlled hot water. Many cylinders are on a controlled supply that can be switched off for short periods. If yours is, reheating may be delayed until the supply is back on.
  • Separately metered hot water. If your hot water is metered and priced separately, time of use rates may apply differently. Your bill shows how your hot water is charged, and our guide to meter types explains the main set-ups.
  • Gas hot water. Gas-heated water doesn't use electricity to heat, so shower timing won't change your power bill.
  • Hot water heat pumps. These use much less electricity to heat the same amount of water. EECA has more on how they work.

Up before the country wakes

The Electricity Authority describes the morning peak as typically running from 7am to 10am, when households everywhere are getting ready for the day. If you're already up before then, your shower can sit comfortably ahead of it.

That suits plenty of people, including:

  • Tradies and early starters heading out before 7am
  • Shift workers finishing or starting in the early hours
  • Early exercisers who shower before work
  • Anyone who likes to get sorted before the rest of the house is up

What a household might look like

Take a four-person household with a mix of morning and evening preferences.

Household member

Shower or bath

Rate window on Night Saver

Early starter, out the door before 7am

5.45am shower

Lower-rate hours

Prefers to shower before bed

9.30pm shower

Lower-rate hours

Teenager, showers after the evening winds down

9.15pm shower

Lower-rate hours

Youngest, bath before dinner

6.30pm bath

Day rate

In this example, three of the four land in the lower-rate hours, and nobody has changed much. Bath time before dinner stays where it is, and that's fine.

Night owls

If you prefer to shower before bed, anything after 9pm is inside the lower-rate window. It also means the bathroom is free for everyone else in the morning.

Pair good timing with less hot water

Timing works best alongside using less hot water in the first place. Our bathroom guide covers each of these in more detail.

  • Shorter showers use less, whatever the time.
  • A lower-flow shower head reduces hot water use every minute.
  • An insulated cylinder and lagged pipes lose less heat.
  • Fixing dripping hot taps stops a slow, steady leak of energy.

EECA estimates that cutting a shower from 15 minutes to 5 saves around 66c each time, which it puts at about $5 per person per week. EECA uses its own flow rate and electricity price assumptions, so that figure is lower than the same change works out to in the table above. Either way, shower length is the single biggest lever, and it works before you think about timing at all.

Hot water safety

As above, EECA advises that hot water should be a minimum of 60°C at the cylinder and no more than 55°C at the tap. Anything higher adds heating cost that could be avoided.

  • Don't adjust your cylinder's thermostat or wiring yourself. Talk to a licensed plumber or registered electrician.
  • If you're considering a timer to concentrate heating in the lower-rate hours, get professional advice first. The cylinder still needs to reach a safe temperature, and a timer won't suit every cylinder or household.
  • Take extra care with water temperature for young children and older family members.
  • Use your bathroom extractor fan to clear steam and keep the room dry.

A mix is normal

School mornings, late finishes and cold winter evenings mean plenty of showers will happen at peak times, and that's okay. Moving even a few of the household's showers into the early morning or late evening makes a difference over a year, alongside other changes in the laundry and kitchen.

Night Saver and Smart Hot Water

Night Saver offers lower rates from 9pm to 7am every night, compared to day rates on the plan. It's an open-term plan and needs a communicating smart meter. It tends to suit early risers, night owls and households that can move energy-heavy tasks outside the day.

Eligible customers on Freedom or Night Saver can also join Smart Hot Water, which pauses supply to your hot water heating at certain times of day and gives you a $10 credit on your bill each month. Terms, conditions and eligibility criteria apply.

If most of your power use happens during the day and can't move, another plan may suit you better. You can compare our plans side by side.

Other useful resources

Important information

  • This guide is general information only. It isn't electrical, plumbing, fire safety, food safety or financial advice, and nothing in it should be relied on as a guarantee of safety or of any particular saving.
  • Always follow the manufacturer's instructions and safety warnings for your appliances and devices, and use a registered electrician or licensed plumber for any electrical or plumbing work. If you're unsure whether something is safe to run while you're asleep or away from home, don't.
  • Any changes to your hot water cylinder, including thermostat settings, timers or wiring, should only be made by a licensed plumber or registered electrician. How and when your cylinder reheats depends on your system, metering and supply arrangements.
  • Energy use and cost figures are indicative estimates based on typical appliances and the national average residential price of 42.1c per kWh (MBIE Quarterly Survey of Domestic Electricity Prices, 15 August 2026). Your actual costs, and any savings, will depend on your plan, rates, network, meter, appliances and how you use them.
  • Night Saver offers lower rates from 9pm to 7am compared to day rates on the same plan. Anticipated savings are based on those lower rates, and actual savings vary based on usage. Night Saver requires a communicating smart meter. Ts&Cs and eligibility criteria apply to all Meridian plans and offers.
  • To the extent permitted by law, Meridian Energy isn't liable for any loss, damage or injury arising from reliance on the information in this guide.

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