You wake up, turn on the shower and discover that the hot water is already running cold.
The tank is not visibly leaking, the rest of the house still has power and the hot water system appeared to be working normally the day before.
For homes with an electric storage hot water system, the problem may involve the off-peak or controlled-load electricity supply. It could also indicate a faulty thermostat, failed heating element, tripped circuit or another electrical issue.
Understanding how off-peak hot water works can help explain why a system sometimes runs out, why it may take hours to reheat and when it is time to call an electrician.
What Is Off-Peak Electric Hot Water?
Off-peak electric hot water is an arrangement where the hot water system is connected to a separate controlled electrical supply.
This is also commonly called:
- Controlled-load hot water
- Economy tariff hot water
- Off-peak hot water
- Tariff-controlled hot water
The hot water system is usually connected through a dedicated circuit rather than drawing electricity continuously from the home’s normal power supply.
In exchange for a lower electricity rate, the network can temporarily interrupt the power supplied to the hot water system. The tank heats when electricity is available and stores the heated water until it is needed.
This arrangement works well when the storage tank is large enough to hold sufficient hot water for the household between heating periods.
How Does an Electric Storage Hot Water System Work?
An electric storage system contains one or more heating elements inside an insulated water tank.
Cold water enters the tank and is heated by the element. A thermostat monitors the water temperature and switches the element on or off as required.
Hot water rises towards the top of the tank, where it is drawn into the home when someone uses a shower, bath or hot water tap.
When hot water leaves the tank, cold water enters to replace it. If a large amount of hot water is used, the water remaining in the tank gradually becomes cooler.
A system connected to the home’s regular electricity supply may begin reheating when the thermostat detects the drop in temperature. A controlled-load system may need to wait until electricity becomes available again.
Why Is Off-Peak Electricity Cheaper?
Electricity demand changes throughout the day. Demand generally increases when many homes use appliances at the same time.
Hot water systems can store heat, so they do not necessarily need electricity every minute of the day. Connecting them to a controlled-load tariff allows the electricity network to manage when the heating element operates.
The homeowner receives a lower rate for the electricity used by the hot water system, but the supply may be unavailable during certain periods.
The exact tariff, electricity price and available heating periods depend on the property, meter configuration and electricity retailer.
Why Have I Run Out of Hot Water?
Running out of hot water does not always mean the tank has failed.
Common causes include increased household use, a tank that is too small, an interrupted controlled-load supply or an electrical fault preventing the water from reheating.
The Household Used More Hot Water Than Usual
Extra showers, visitors, baths, laundry and washing dishes can use more stored hot water than the system normally needs to provide.
Once the heated water has been used, a controlled-load system may not begin reheating immediately.
The household may then need to wait until the next period when power is supplied to the heating circuit.
The Tank Is Too Small for the Household
A hot water tank needs enough storage capacity to meet the household’s demand between heating periods.
A system that worked for one or two occupants may struggle when more people move into the home or household routines change.
Regularly running out of hot water at approximately the same time each day can indicate that the household is using the full stored capacity of the tank.
The Water Is Taking Longer to Heat During Winter
During colder weather, the water entering the tank is colder and households may take longer or hotter showers.
This means the system must use more energy to bring the incoming water up to temperature while the household may also be consuming more hot water.
An older or marginally sized system may become noticeably less effective during winter, even though it appeared adequate during warmer months.
The Heating Element Has Failed
The heating element is the component responsible for heating the water inside the tank.
If the element fails, the system may stop heating altogether or provide only a limited amount of hot water.
Some larger tanks contain more than one element. If one element fails, the system may still produce some hot water but take much longer to recover or run cold sooner than expected.
The Thermostat Is Faulty
The thermostat controls when the heating element switches on and off.
A faulty thermostat may prevent the element from operating, switch it off too early or cause inconsistent water temperatures.
Thermostats and heating elements are located within hard-wired electrical equipment and should only be tested or replaced by an appropriately licensed professional.
The Circuit Breaker or Safety Switch Has Tripped
An electrical fault may cause the hot water circuit breaker or safety switch to trip at the switchboard.
This can occur because of a failed element, damaged wiring, moisture entering electrical components or another fault within the circuit.
Repeatedly resetting a breaker without identifying why it is tripping is not a repair. If it trips again, leave the circuit off and arrange for an electrician to inspect it.
The Hot Water Isolation Switch Is Off or Faulty
Some hot water systems have an isolation switch near the tank or within the electrical installation.
The switch may have been turned off accidentally, or the switch and its connections may have deteriorated over time.
Burn marks, heat damage, buzzing or a burning smell around an isolation switch require prompt electrical attention.
There Is a Problem With the Controlled-Load Supply
The issue may not be inside the hot water tank itself.
A fault involving the meter, controlled-load receiver, contactor or associated wiring may prevent electricity from reaching the system during the normal heating period.
This can make the hot water system appear faulty even when its thermostat and heating element are operational.
An electrician can test whether power is reaching the hot water circuit and determine where the supply is being interrupted.
The Tank or Pipework Is Leaking
A leaking tank, relief valve or hot water pipe can cause heated water to be lost faster than expected.
The system may continue attempting to heat replacement water, increasing electricity use while providing less usable hot water.
Electrical faults should be inspected by an electrician, while leaking tanks, valves and plumbing generally require a plumber. In some cases, both trades may be needed.
Why Do I Have Hot Water in the Evening but None in the Morning?
This pattern can occur when the household uses most of the stored hot water before the controlled-load circuit has completed its next heating cycle.
It may also indicate that the system is only partially reheating because of a faulty element, thermostat or interrupted electricity supply.
Keep track of when the hot water becomes cold and when it returns. A consistent timing pattern can help the electrician determine whether the problem relates to household demand, tariff timing or an intermittent electrical fault.
Why Does the Hot Water Return Several Hours Later?
If the hot water returns without anyone resetting the switchboard or repairing the system, the tank may have reheated when the controlled-load electricity supply became available again.
This can happen after the household has simply used all the stored hot water.
However, recurring loss of hot water should not automatically be dismissed as normal off-peak operation. An undersized tank, faulty component or supply problem may be reducing the amount of hot water available.
How Do I Know Whether My Hot Water Is on a Controlled-Load Tariff?
Your electricity bill may show a separate tariff or usage category for controlled-load, economy or off-peak electricity.
You may also notice separate metering equipment or a labelled hot water circuit in the meter box or switchboard.
Terminology varies between electricity retailers, so contact your retailer if you are unsure which tariff applies to the property.
An electrician can inspect the installation and determine how the hot water system is supplied.
What Is a Hot Water Boost Switch?
Some controlled-load hot water installations include a boost function.
A boost allows the system to heat using the home’s normal electricity supply rather than waiting for the next controlled-load period.
This can be useful when the household has unexpectedly used all the stored hot water.
Not every property has a boost circuit, and the way it operates varies between installations. Boost electricity may also be charged at the property’s normal tariff rather than the cheaper controlled-load rate.
If you do not know whether your property has a boost function, have the switchboard and hot water circuit inspected rather than experimenting with unidentified switches.
Should I Move My Hot Water System Off the Controlled-Load Tariff?
Moving the system to a permanent electricity supply may allow it to reheat whenever the thermostat calls for heat.
However, it may also increase electricity costs because the system will no longer use the same controlled-load rate.
Before changing tariffs, consider:
- How often the household runs out of hot water
- Whether the tank is correctly sized
- Whether an electrical fault is reducing its performance
- The cost difference between available tariffs
- Whether switchboard or metering work is required
- Whether a boost circuit would solve the problem
- Whether the hot water system is due for replacement
Your electricity retailer can explain available tariff options. A licensed electrician can assess the existing circuit, metering arrangement and any electrical work required.
Can Solar Power Be Used to Heat an Electric Hot Water System?
Some homes with rooftop solar use timers, controllers or dedicated energy-management systems to operate an electric hot water element while solar power is being generated.
This can reduce the amount of electricity imported from the grid, but the system must still heat for long enough to provide sufficient hot water and operate safely.
Moving a hot water system between controlled load, normal supply and solar-controlled operation requires proper electrical assessment. It is not simply a matter of plugging the tank into a timer.
What Can You Safely Check When the Hot Water Stops Working?
Homeowners can make several basic observations without opening electrical covers or touching internal components.
- Check whether the rest of the property has power
- Look for a clearly labelled hot water breaker or safety switch
- Check whether a breaker has tripped
- Look for visible water leaking around the tank
- Check the electricity bill for a controlled-load tariff
- Note when the hot water stopped and whether it later returned
- Listen for unusual buzzing or crackling
- Check for burning smells or visible heat damage
Do not remove the electrical cover from the hot water system, test wiring or attempt to replace an element or thermostat yourself.
If a breaker has tripped repeatedly, the switch or wiring smells burnt, or there are signs of electrical damage, leave the circuit off and contact a licensed electrician.
Does the Hot Water System Need Repairing or Replacing?
A failed thermostat, element, switch or electrical connection may be repairable.
Replacement may be more practical when the tank is leaking, badly corroded, repeatedly failing or approaching the end of its serviceable life.
The best decision depends on:
- The age of the system
- The condition of the storage tank
- The cause of the fault
- The cost and availability of replacement components
- Whether the tank is correctly sized
- The household’s future hot water needs
- The potential efficiency of a replacement system
Fault finding should identify whether the problem is with the tank, the electrical components, the controlled-load supply or the household simply using more stored water than the system can provide.
Electric Hot Water Repairs in Moreton Bay
Power Bolt Electrical provides electric hot water system fault finding and repairs for homeowners, landlords and property managers.
We can inspect hot water circuits, circuit breakers, safety switches, isolation switches, thermostats, heating elements and controlled-load supply issues.
Power Bolt Electrical services Narangba, North Lakes, Burpengary, Morayfield, Caboolture and surrounding Moreton Bay areas.
If your electric hot water system has stopped heating, keeps tripping or is running cold sooner than expected, contact Power Bolt Electrical to arrange an inspection.