Fast read
A hot water timer allows an electric storage hot water system to run during the middle of the day when solar panels are producing electricity. Instead of exporting excess solar energy for a low feed-in tariff, that energy can heat your water. This increases solar self-consumption and can significantly reduce electricity costs, making it one of the simplest ways to improve solar savings.
What Is a Hot Water Timer?
A hot water timer is a simple device installed by an electrician that controls when your electric hot water system turns on. Instead of allowing the system to heat water automatically at any time, the timer allows you to schedule heating during specific hours.
Many homes heat water overnight using an off-peak electricity tariff. This was traditionally cheaper than daytime electricity. However, once solar panels are installed, the cheapest energy available is often the solar power generated during the middle of the day.
A timer allows your hot water system to operate when your solar panels are producing the most energy.
Why Does Timing Matter for Solar Savings?
Solar panels typically produce the most electricity between late morning and mid-afternoon. If your home is not using all that energy at the time, the excess electricity is exported to the grid.
Feed-in tariffs are usually much lower than the price of electricity you buy from the grid. In many areas, households might earn only 5 to 10 cents per kilowatt-hour for exports while paying significantly more to buy electricity later.
By running your hot water system during the middle of the day, that excess solar energy can be used to heat water instead of being exported cheaply.
How Much Could a Timer Save?
A typical electric storage hot water system can use around 4 kilowatt-hours of electricity per day. If that energy is purchased from the grid at around 20 cents per kilowatt-hour, the annual cost can approach several hundred dollars.
If that same energy is supplied by solar instead of grid electricity, those costs can be greatly reduced. In this way, the hot water tank effectively acts as a simple form of energy storage by absorbing excess solar generation.
This approach is often one of the easiest and most affordable ways to increase solar self-consumption.
Are Hot Water Timers Suitable for Every Home?
Hot water timers are most suitable for electric storage hot water systems that use a large tank to store heated water. They are not compatible with instantaneous hot water systems that heat water only when needed.
The home also needs sufficient solar production to supply the additional daytime load. If the solar system is small or the home already uses most of its solar generation during the day, there may not be enough surplus energy available.
More advanced devices known as solar diverters can optimise this process automatically, but a simple timer is often a much cheaper and practical starting point.
