Hot Water Tariffs, Off-Peak & Timers.
Hot Water Tariffs, Off-Peak & Timers
The cheapest time to heat your water depends on your tariff, solar, system and how much hot water your home needs.
Use the control checker to compare general electricity, controlled load, off-peak hot water, daytime solar, timers, free-power periods and solar-aware controls for electric storage and heat pump systems.
How Should My Hot Water Run?
This does not select an electricity retailer. It identifies the type of heating schedule or control strategy worth comparing for your hot water setup.
Guide only. Electricity tariff names, rates, switching times and eligibility vary by retailer, distributor, state and property. Confirm the actual supply arrangement and electrical requirements before changing how a hot water system is connected or controlled.
What Is the Best Electricity Tariff for Hot Water?
There is no single best tariff for every hot water system. The right arrangement depends on the type of water heater, tank capacity, household demand, available controlled-load supply, solar PV and how much flexibility you have around heating times.
General Supply vs Controlled Load vs Solar Timing
These arrangements solve different problems. One prioritises availability, another reduces the electricity rate, and another attempts to use electricity generated at the property.
| Arrangement | When It Heats | Main Advantage | Main Limitation | Often Suits |
|---|---|---|---|---|
| General Supply | Whenever the thermostat or controller calls for heat | Maximum recovery flexibility | Electricity may cost more than a dedicated controlled-load rate | Smaller tanks, heavy users, systems requiring flexible recovery |
| Controlled Load | During network-controlled availability periods | Lower electricity rate may reduce running cost | Recovery is unavailable outside the supply window | Adequately sized electric storage and some eligible heat-pump arrangements |
| Fixed Daytime Timer | At chosen daytime hours | Can shift heating toward likely solar production | Timer does not know whether solar surplus actually exists | Homes with rooftop PV and predictable generation |
| Solar-Aware Control | According to available solar or configured load conditions | Better matches heating with actual PV surplus | More complex than a basic timer | Solar homes wanting to minimise grid imports |
| Free-Power Window | During the qualifying retailer period | Can significantly reduce purchased energy cost | Tank and recovery must cover enough demand inside the available window | Storage systems that can shift a meaningful amount of heating |
What Is Off-Peak Hot Water?
Off-peak hot water usually means the water heater is supplied through a separate or controlled electricity arrangement that makes power available during selected lower-demand periods rather than continuously.
Cheaper Energy
The main reason for controlled-load hot water is the possibility of paying a lower electricity rate for the dedicated water-heating circuit.
Restricted Recovery
If the network is not supplying the controlled circuit, the tank cannot simply reheat because the household has used more water than expected.
Tank Size Matters
Restricted heating works best when the tank stores enough usable hot water to carry the household between available heating periods.
Tariff 11, Tariff 31 & Tariff 33: What Do They Mean?
These tariff numbers are commonly recognised in Queensland, but they should not be treated as universal Australian electricity terminology.
Tariff 11
Commonly used as a Queensland reference to general household electricity supply. A hot water system connected to general supply can generally recover whenever its thermostat or controller requires power.
Tariff 31
Commonly associated with a more restricted controlled-load arrangement historically used for equipment such as electric storage hot water.
Tariff 33
Commonly associated with a controlled-load arrangement offering a broader availability window than the most restricted option, depending on the applicable network and retail arrangement.
Best Heating Strategy for Electric Storage Hot Water
Electric storage is highly flexible because the tank can act like a thermal battery. The trade-off is between electricity price, available heating time and the amount of hot water stored.
Controlled Load
Can suit a correctly sized tank where lower electricity pricing is valuable and the household has enough storage to bridge the restricted heating period.
General Supply
Provides more flexible recovery and may suit high-demand homes, undersized existing tanks or households that frequently exhaust stored hot water.
Daytime Solar
Rooftop PV can be used to heat the tank during the day, effectively storing some household solar energy as hot water for later use.
Best Heating Time for a Heat Pump Hot Water System
Heat pumps behave differently from standard resistance tanks. They use much less electrical input but generally take longer to recover, and their efficiency can change with ambient temperature.
Daytime Can Help Efficiency
In many climates, warmer daytime air can provide better operating conditions than the coldest part of the night.
Daytime Can Match Solar
If rooftop PV is available, daytime operation gives the household an opportunity to supply some of the heat pump's electrical demand locally.
Recovery Window Still Matters
A very short heating window can be unsuitable if the compressor cannot restore enough tank energy before the next major household demand period.
Should Hot Water Run on a Timer With Solar Panels?
A daytime timer is one of the simplest ways to move hot-water heating toward solar-production hours, but it is still only a schedule.
What a Timer Does Well
- Simple and predictable.
- Can shift operation away from evening peaks.
- Can align approximately with daytime PV production.
- Useful where the household has consistent generation and demand.
What a Timer Cannot Know
- Whether clouds have reduced PV generation.
- Whether the oven, air conditioner or EV is already using the solar.
- Whether surplus generation exists at that exact moment.
- Whether the tank needs a full heating cycle.
Timer vs Solar-Aware Hot Water Control
Both can move heating into the daytime. The difference is whether the control follows a clock or reacts to actual household energy conditions.
Fixed Timer
Turns the system on or makes heating available according to the programmed schedule regardless of actual solar production.
Solar-Aware Relay
Can be configured to respond to measured generation, export or household load conditions before enabling hot-water heating.
Which Is Better?
A timer is simpler. Solar-aware control can use changing PV conditions more intelligently, but the additional hardware and installation should justify the expected benefit.
Using Free-Power Periods for Hot Water
A free-power period can make a storage water heater valuable as a controllable household energy load — provided enough of the day's heating can fit inside the available window.
Tank Capacity
The tank must store enough usable hot water after the free period to meet demand until the next heating opportunity.
Heating Output
A three-hour window only works if the element or compressor can put enough useful heat into the tank during those three hours.
Backup Heating
Larger households may still need recovery outside the free period after unusually high use, poor heat-pump conditions or unexpected demand.
Why Off-Peak Hot Water Can Run Out
Running out does not automatically mean the water heater is faulty. The system may simply have used its stored capacity before electricity becomes available again.
Tank Too Small
The stored litres may no longer suit the number of occupants or current household habits.
Higher Usage
Longer showers, teenagers, baths or multiple consecutive showers can exhaust the available storage earlier.
No Midday Recovery
A controlled-load system may remain electrically unavailable even though the thermostat is calling for heat.
Faulty Heating
A failed element, thermostat or other system fault can also reduce available hot water and should not be confused with normal tariff limitations.
Heat Pump Recovery
Heat pumps typically recover more gradually than large resistance elements or gas burners, so available operating time matters.
Mixing / Tempering
Delivered hot-water performance can also be affected by tempering equipment, stored temperature and plumbing conditions.
How to Choose a Hot Water Tariff or Heating Schedule
Check the System
Electric storage and heat pumps have different recovery speeds and operating characteristics.
Check the Supply
Confirm whether the property has general supply, controlled load or another dedicated circuit arrangement.
Check Solar & Plans
Rooftop PV or a retailer free-power window can create a completely different preferred heating period.
Check Capacity
Make sure the tank and recovery rate can meet household demand within the proposed heating window.
Hot Water Tariff, Off-Peak & Timer FAQs
What is off-peak hot water?
Off-peak hot water generally refers to an electric water heater supplied through a controlled or dedicated electricity arrangement where power is made available during selected periods rather than continuously.
Is off-peak hot water cheaper?
It can be because controlled-load electricity may be priced below general household electricity. The trade-off is that the water heater may not be able to recover whenever the household wants it to.
What is the difference between Tariff 11 and Tariff 31?
In common Queensland terminology, Tariff 11 refers to general household supply while Tariff 31 has historically referred to a more restricted controlled-load arrangement. Exact retailer and network arrangements should always be confirmed because tariff names and availability change.
What is Tariff 33 hot water?
Tariff 33 is a Queensland-style controlled-load reference commonly associated with a broader electricity availability window than the most restricted controlled-load option. Exact supply hours and retailer terms should be confirmed for the property.
Should I put my heat pump on off-peak?
Not automatically. A controlled-load rate may reduce the electricity price, but a heat pump also needs enough operating time to recover the tank. Daytime operation can additionally benefit from warmer ambient conditions and rooftop solar at some homes.
What time should a heat pump hot water system run?
The preferred time depends on household demand, climate, solar PV, electricity tariff and recovery requirements. Homes with solar often compare daytime operation, while homes without solar may compare controlled-load pricing against the flexibility of general supply.
Should electric hot water run during the day with solar panels?
It can make sense where useful surplus solar is available. A timer can move heating toward daytime generation, while solar-aware control can respond more directly to actual household export or generation conditions.
Is a timer enough for solar hot water control?
A timer may be sufficient where solar production is predictable and simplicity is the priority. It cannot measure actual available surplus, so a solar-aware controller can potentially use variable solar production more precisely.
Why does my off-peak hot water run out?
Possible causes include insufficient tank capacity, increased household demand, limited controlled-load heating time, a heating fault or slower recovery than the household requires.
Can a free-power period run my hot water system?
Potentially. The tank and heater must be capable of producing enough useful hot water during the free period to cover demand until the next heating opportunity. Larger households may still require additional recovery outside the free window.
Does changing tariff make an electric hot water system more efficient?
No. A tariff changes the price or availability of electricity rather than the efficiency of a resistance heating element. The same amount of electrical energy is still required to produce roughly the same amount of resistance heat.
Can I move my hot water system from controlled load to general supply?
The electrical arrangement may be able to be changed, but it requires assessment of the existing circuit, meter arrangement, retailer or network requirements and applicable electrical rules. A licensed electrician should confirm the available options.
Choose the Hot Water System and the Way You Want It to Run.
Tank size, system technology, tariff and heating schedule all work together. Compare the complete setup rather than choosing the water heater and worrying about the electricity arrangement later.
