For most Queensland households, the biggest driver of electricity costs is not a single large appliance — it is the combination of everything running between 5pm and 9:30pm. Air conditioning, cooking, hot water, entertainment systems, and device charging all run simultaneously during the window that Queensland's time-of-use tariff classifies as peak pricing. Understanding evening electricity costs and how battery storage offsets them is the most direct way to evaluate whether a home battery makes financial sense.

Why the Evening Window Drives Your Bill

Queensland's Energex network introduced a default time-of-use tariff from 1 July 2025 for customers with smart meters. The peak period runs from 4pm to 9pm on weekdays — precisely the period of highest residential consumption. Regional Queensland customers on Ergon Energy's TOU tariff face the same structure.

For households on a flat-rate tariff, approximately 29–33c per kWh still means that electricity consumed in the evening is significantly more expensive than stored solar. Whether you are on flat-rate or TOU, reducing how much grid power your household consumes between 5pm and 9:30pm is the most powerful lever available. Battery storage pulls that lever automatically, every single day.

Air Conditioning — The Dominant Evening Load

Ducted Reverse-Cycle Air Conditioning

A 7kW ducted reverse-cycle system operating from 4:30pm to 9:30pm on a warm Queensland day consumes approximately 10–15kWh. At an average grid electricity rate of 30c per kWh, a 12kWh air conditioning load during peak hours costs $3.60 that evening.

Across a 90-day Queensland summer: $300–$450 from air conditioning alone

In Queensland, reverse-cycle air conditioning is not optional for most households. During summer months — and increasingly during shoulder seasons — ducted or split-system air conditioning runs consistently through the evening. A correctly sized battery absorbs this load automatically, replacing expensive grid power with stored solar.

Hot Water Systems

Electric Hot Water Storage

An 80–160 litre electric hot water storage system typically consumes 3–5kWh per heating cycle. If the system heats water in the evening, it adds $0.90–$1.50 to peak electricity costs in a single cycle.

Simple fix: set the heating schedule to 9am–3pm to use cheap solar instead

The simplest optimisation for electric hot water is a schedule change — set the system to heat between 9am and 3pm using solar generation or off-peak electricity, rather than heating in the evening when peak rates apply. This is a free change that reduces your bill immediately, before any solar or battery investment.

Cooking and Kitchen Loads

Oven, Cooktop, and Kitchen Appliances

A standard electric oven at 180–200 degrees Celsius consumes approximately 1.5–2kWh per hour. Combined with a cooktop, rangehood, and dishwasher, the kitchen can add 3–5kWh to the evening load. Microwave ovens are more efficient and worth using as a substitute for the oven where practical.

Evening kitchen load: 3–5kWh, worth approximately $0.90–$1.50 per night

How Battery Storage Addresses These Loads

A correctly sized home battery automatically intercepts all these loads during the peak window, replacing grid electricity with stored solar. The system charges during the day when solar generation is high and off-peak rates apply, then discharges from 4pm onwards. No user intervention required — the inverter manages the discharge schedule automatically.

A 10kWh battery supplying 8–9kWh of usable energy can handle a substantial portion of the evening load described above, depending on air conditioning intensity. On a mild Queensland evening with moderate air conditioning, 8–9kWh is sufficient to cover most of the peak window. On a peak summer night with heavy air conditioning, you may need more capacity.

Sizing for Your Actual Evening Load

The key word is correctly sized. A battery that covers 4 hours of evening consumption and runs out at 8pm still leaves the household exposed to grid rates for the remainder of the peak window. The savings calculation depends entirely on how well the battery capacity matches your specific evening load profile.

Source Energy Group conducts a detailed energy audit of your actual consumption before recommending a system — specifically to ensure battery capacity matches your real evening load pattern, not a generic estimate. We review your interval data, identify your consumption peaks, and size the system to cover the window that matters most.

If your electricity bills have continued to rise despite having solar panels — or if you are considering adding storage to an existing system — a free energy audit with Source Energy Group will identify exactly how much of your peak electricity cost could be offset by a correctly-sized battery.

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