Peak Electricity Rates: How Batteries Save Money

If you are a Queensland homeowner on a time-of-use electricity tariff, the time of day you use power has a direct impact on what you pay. Electricity costs more during peak demand periods and less during off-peak times. Battery storage is specifically designed to exploit that gap — charging when power is cheap and discharging when it is expensive.

How Queensland's Time-of-Use Tariff Works

Residential electricity in South East Queensland (SEQ) is distributed by Energex. From 1 July 2025, Energex assigned customers with smart meters to a default Time-of-Use (TOU) tariff under its new 2025–30 tariff structure. The peak period — the most expensive window — runs from 4pm to 9pm on weekdays. The off-peak period runs from 11am to 4pm.

Overall, residential electricity usage rates in Queensland range from approximately 26c to 33c per kWh depending on the retailer and plan, plus a daily supply charge. Regional Queensland is served by Ergon Energy, where the Queensland Competition Authority (QCA) sets regulated prices. Ergon's residential TOU tariff (Tariff 12D) similarly applies higher rates during peak periods.

Why Solar Panels Alone Don't Close This Gap

Solar panels generate most of their output between roughly 9am and 3pm — the middle of the day, during the off-peak window. Most Queensland households consume the most electricity between 4pm and 9pm — the peak window, after solar generation has significantly declined or stopped.

Excess solar exported to the grid earns feed-in tariffs ranging from 1c to 8c per kWh — substantially below the retail rate households pay to purchase electricity during the evening peak. Sending solar to the grid during the day and buying expensive grid power in the evening is a poor financial exchange. Battery storage eliminates that exchange entirely.

How Battery Storage Closes the Gap

A home battery charges from excess solar during the day when electricity is cheap. From 4pm onwards, the battery discharges automatically, supplying your household with stored solar instead of grid power. The economics are straightforward: instead of exporting solar at 5c and buying grid power at 30c, you store the solar and consume it at home during the peak window.

A 10kWh battery supplying 8–9kWh of usable energy during the peak window — at a cost-offset of 30c per kWh — delivers $2.40–$2.70 in daily savings from peak-shifting alone. Over a full year, that is $876–$985 in savings purely from the time-of-use arbitrage, before any VPP earnings or feed-in tariff credits are counted.

Getting the System Sized Correctly

The savings from peak-shifting depend entirely on whether your battery has enough capacity to cover your evening consumption. A battery that runs out at 6pm leaves the most expensive part of the evening window — 7pm to 9pm — uncovered. A household with high air conditioning use in summer needs more battery capacity than a household with moderate evening loads.

This is why off-the-shelf 6.6kW solar with a 10kWh battery is not the right answer for every household. The correct system size depends on your actual consumption data — not an industry default.

Source Energy Group conducts a detailed energy audit of your actual consumption patterns before recommending a system. We review your interval data if available, identify your peak window consumption, and size the battery to match the load — not to hit a price point.