News articles grab attention with stories that electricity utilities may want to turn off rooftop solar PV systems at times, and to turn off air conditioning systems at other times.
What you won't find are articles on how appliances provide options for individuals and businesses themselves to adjust their energy production and consumption to best support the electricity grid. These options do not require any power for electricity utilities to interfere in how people run their own homes and businesses.
How a Hot Water System can provide 4 kilowatt hours or more energy storage
Many hot water systems are designed to operate as follows:
- Heat water to a minimum of 60℃. This is to prevent the growth of harmful bacteria.
- Ensure water is delivered from the hot water system at no more than 50℃. This is to lower the risk of scald injuries.
- Optionally, heat water to a maximum of 70℃ or 75℃. This is to allow more hot water, at 50℃, to be available.
The delivery temperature of 50℃ is achieved by mixing the stored hot water with some cold water in a Temperature Limiting Device.
The amount of energy needed to heat 90 litres of water from 60℃ to 70℃ is 1 kilowatt hour.
A 360-litre Hot Water System, for instance, can be used to store 4 kilowatt hours of electrical energy by raising the temperature of water in it from 60℃ to 70℃.
There is no need to buy a battery to store energy if you own a suitable Hot Water System.
The Argument for Smart Switches
Time of Use charging has long been proposed to "encourage" electricity consumers to avoid using electricity at times when demand is highest. However, if you examine the National Electricity Market data, you will find that this is not especially helpful. The reason is that there are periods of extremely high wholesale (NEM) prices when demand is relatively low, and conversely, there are times when there are very low wholesale prices when demand is quite high. Moreover, these intervals do not conveniently coincide with any particular time of the day that "Time of Use" charging requires.
It is more appropriate to adjust the system so that electricity is preferable consumed when the wholesale (NEM) price is relatively low, and avoid consuming electricity at this times when the price is extremely high. This can be implemented with "smart chargers" that examine the NEM price before deciding whether to store energy - in a Hot Water System, an Electric Vehicle Battery, or a Home Battery.
Analysis of the National Electricity Market Data for NSW in November and December 2024 (see "How to lower the price of electricity") that shows that the price of electricity consumed in a small proportion of the time contributed enormously to the overall cost of electricity consumed in those months. Smart switches that help to reduce electricity consumed in such periods, and preferable store more electricity whenever the price is relatively low, can lower the total cost.
