Using a timer to heat your hot water cylinder with cheap night electricity instead of daytime electricity can save hundreds of dollars every year for a relatively small installation cost.
Heating water overnight also reduces electricity demand during peak hours and helps make better use of New Zealand’s renewable electricity.
Is this right for your home?
This approach works best if you:
- have a standard electric hot water cylinder
- have a day/night electricity plan (or are interested in signing up for one)
- use most of your hot water during the day
Typical savings example
| Scenario | Without timer | With timer | Savings |
| 7 kWh/day at 29c | $2.03/day | ||
| 7 kWh/day at 12c night rate | $0.84/day | ||
| Savings | $1.19/day ($434/year) |
Your actual savings will depend on your electricity prices and how much hot water your household uses. For some homes the savings may be smaller, while others may save significantly more.
How to estimate your own savings
- Check your latest electricity bill for your day rate and night rate (price per kWh).
- Estimate how much electricity your hot water uses each day. For a family of 4 it’s often about 7 kWh.
- Use this simple formula:
(day rate – night rate) × daily hot water energy × 365(0.29 - 0.12) x 7 x 365 = $434/year
Typical installation cost
Most installations cost $300–$500 depending on the switchboard and wiring. For many homes this means the timer pays for itself within the first year.
Things to be aware of
Cylinder temperature and safety
Your hot water cylinder should reach 60 °C at least once each day to prevent the risk of Legionella bacteria. Your electrician can confirm that the cylinder thermostat is set correctly and that the timer allows enough heating time.
Running out of hot water
If your household uses a lot of hot water in the morning, a cylinder that heats only at night may run low by evening. In this case, the timer can be programmed to allow a short daytime heating period, although this will slightly reduce the savings.
Occasional heavy usage
If you have guests staying or are using more hot water than usual, a timer can usually be temporarily overridden so the cylinder heats normally.
Hardware
This Bluetooth hot water timer kit allows the heating schedule and overrides to be controlled with bluetooth from your phone: https://eurotechnz.co.nz/products/bluetooth-hot-water-cylinder-control-kit
Your electrician may also suggest other timer options depending on your switchboard and setup.
Get a quote for a hot water timer
Ask your electrician for a quote to install a hot water cylinder timer.
You may find it helpful to send them this page so they know exactly what you are asking for:
https://electrifydunedin.nz/hot-water-timer
Once you have a quote, simply compare the installation cost with your estimated annual savings to see how quickly the timer will pay for itself.
For electricians
Install a timer controlling the hot water cylinder circuit and program overnight heating (for example 11 pm – 4 am). Ensure the cylinder thermostat allows the tank to reach 60 °C daily.
