How to Optimise Time-of-Use Tariffs at Home
A cheap solar system can still deliver expensive bills if your household buys power at 6 pm, when the tariff is at its highest. The real win is to optimise time-of-use tariffs around the way your home actually uses energy: capture solar when it is plentiful, shift flexible loads away from peak periods, and use a battery strategically rather than simply letting it run flat overnight.
For Adelaide households, this can be the difference between having solar panels on the roof and running a genuinely lower-cost, more independent home. But it is not a set-and-forget exercise. Your retailer plan, household load profile, battery size, inverter settings and backup priorities all matter.
What a time-of-use tariff really changes
A flat electricity tariff charges the same rate all day. A time-of-use tariff charges different prices based on the time electricity is used. Peak periods are usually in the late afternoon and evening, when households return home, cook dinner, run heating or cooling, and switch on appliances. Shoulder periods are cheaper, while off-peak periods may apply overnight or during lower-demand windows.
Some plans also offer free electricity windows in the middle of the day. These can be valuable, particularly for homes without enough solar generation in winter, homes with EVs, or households using heat-pump hot water. Free power is not automatically a bargain, though. A plan with free midday energy can still have a very high peak rate or daily supply charge. The numbers need to work across your whole bill.
The goal is simple: avoid buying electricity during the costly window wherever possible. Solar, batteries and smart appliances each have a different job in making that happen.
Start with your interval data, not a sales pitch
Before changing plans or programming a battery, look at your electricity usage by time of day. Most retailers provide interval data through their app or online portal. It shows when your home imports energy from the grid and, in many cases, when it exports solar.
Look closely at three periods: the morning ramp-up, the late-afternoon to evening peak, and overnight consumption. A family that cooks with electricity, runs reverse-cycle air conditioning and charges an EV after work has a very different profile from a couple who are home during the day.
Also check your seasonal pattern. Adelaide summers can produce strong solar output but high late-day cooling demand. In winter, solar production falls just as heating, hot water and cooking loads rise. A tariff that looks excellent in a sunny March billing period may be much less attractive in July.
Your electricity bill should be treated like a household energy map. It tells you whether the biggest opportunity is more solar self-consumption, peak shaving with a battery, off-peak charging, or simply moving a few major loads by a few hours.
Optimise time-of-use tariffs with solar and storage
Solar panels make their best contribution in the middle of the day, but household demand often peaks after the sun drops. That gap is why battery storage matters. Instead of exporting surplus solar for a modest feed-in credit, a battery can store it for the high-price evening period.
The best battery strategy is not always to charge to 100 per cent as early as possible. If your system allows it, reserve capacity can be useful when an evening peak is coming or when a blackout is possible. A battery that empties at 8 pm and forces you to buy expensive peak electricity later has not been programmed around your real load.
A practical setup often prioritises solar charging during the day, then discharges through the expensive evening window. If your retailer offers genuinely cheap overnight power, the battery may also be set to grid-charge during that period and discharge during peak pricing. This is tariff arbitrage: buying lower-cost electricity, storing it, and avoiding a higher-cost purchase later.
The maths depends on battery efficiency, tariff spread and battery cycling. If off-peak electricity costs 20 cents per kWh and peak electricity costs 50 cents per kWh, charging a battery overnight can make sense even after allowing for round-trip losses. If the price gap is small, cycling the battery from the grid may save very little while adding wear. Solar charging should usually remain the priority where available.
Size the battery for the evening, not just the brochure
Battery capacity needs to suit how much energy your home uses after solar production drops. A 10 kWh battery may cover a modest evening load, but a larger household with air conditioning, induction cooking, a pool pump and EV charging can burn through that capacity quickly.
Power output matters too. Capacity tells you how long a battery can run. Inverter output tells you how much it can run at once. A high-capacity battery paired with an undersized inverter may struggle to cover several heavy appliances operating together. Three-phase homes need particular care, because phase configuration affects what can be supplied during normal operation and, for some systems, during backup.
For households chasing blackout resilience as well as bill savings, do not use every stored kilowatt-hour each night. Setting a backup reserve means keeping part of the battery untouched. It can slightly reduce everyday savings, but that trade-off may be worthwhile during storm season or in areas with less reliable supply.
Shift the loads that do not care about the clock
Your dishwasher does not mind whether it runs at 1 pm or 8 pm. Neither does a pool pump, laundry cycle or heat-pump hot water system. Moving these loads into solar-rich or low-cost periods is often the cheapest improvement because it does not require additional hardware.
Use appliance delay-start functions, smart plugs where suitable, timers, and energy-management controls. The aim is not to run everything at once during a free-power period. That can create unnecessary demand and may exceed your inverter or switchboard capacity. Spread discretionary loads where practical.
Hot water deserves special attention. An electric storage tank or heat-pump hot water unit is effectively a thermal battery. Heating water during a solar surplus or cheap daytime period stores energy for showers later that evening. For many homes, this is a more cost-effective first step than installing a larger electrical battery solely to cover hot water.
Pool owners can usually run filtration during daylight hours. If the pool needs longer run times in hot weather, schedule the bulk of it through the solar window and only use off-peak time as needed. The same thinking applies to ducted air conditioning: pre-cool or pre-heat the home while solar is strong, then maintain the temperature through the evening instead of starting from scratch at peak tariff time.
EV charging can make or break the plan
An EV is one of the largest flexible loads in a home, and it can either supercharge savings or wipe them out. Plugging in at 6 pm on a high peak tariff is usually the expensive option. Charging from excess solar during the day is ideal, but it may not suit commuters who need the car away from home.
A smart EV charger gives you more control. You can schedule overnight charging on a low off-peak rate, limit charging to solar surplus, or use a combination depending on the next day’s driving needs. Avoid setting the battery and EV charger to compete for the same solar energy unless the system’s controls are designed to manage those priorities.
For most homes, it makes sense to protect enough battery energy for the evening household load before sending every spare solar kilowatt to the car. If your export rate is very low and the car is home during the day, solar EV charging can be excellent value. If the car returns late and your overnight tariff is cheap, scheduled grid charging may be the better choice.
Check the traps before switching electricity plans
Time-of-use plans are not automatically cheaper. Retailers can structure peak times, supply charges, controlled-load rates and feed-in tariffs very differently. Read the tariff schedule rather than relying on a headline such as “free energy” or “super off-peak”.
Compare your likely annual cost using your actual interval data. Pay attention to whether weekends are priced differently, whether the free period has a usage cap, and whether your solar feed-in rate changes after a set export amount. If you have a controlled-load hot water circuit, check how it is billed and whether changing plans affects it.
Battery settings should also be reviewed after a tariff change. A battery operating on yesterday’s schedule can quietly miss the new cheap window or discharge before the most expensive period begins. Many hybrid inverters allow charge and discharge schedules, reserve settings and export controls, but the right configuration depends on your system and electricity plan.
Make the system work as one
The strongest results come from treating solar, battery storage, hot water, EV charging and tariffs as one connected household energy system. Start with the tariff windows, then decide where solar should go first: direct household use, battery charging, hot water, EV charging or export. There is no single setting that wins for every home.
A household with a large evening load may put battery reserve and peak discharge first. A home with a daytime EV and modest night usage may favour solar charging for the car. A family using lots of winter heating may benefit more from controlled heating schedules and sufficient battery power output than from chasing a high feed-in tariff.
If you are planning a solar-and-battery upgrade in South Australia, OG Trade can help match battery capacity, hybrid inverter capability and backup requirements to the way your household uses energy. The best deal is not just the sharpest installed price. It is the system that keeps expensive grid imports down when your bill is most exposed.
Start with one billing cycle of data, make one or two meaningful changes, then check the result. A better tariff setup is built from real household behaviour, not guesses - and every kilowatt-hour shifted away from peak pricing gives your solar investment more to do.