How to read your electricity bill before getting solar or battery quotes

A retailer can only size a system well if they know how you use power, and you can only judge their savings claims if you know your own numbers. Ten minutes with two recent bills, one from summer and one from winter, gives you both.

The numbers to find

Daily use: the number that sizes your system

Your bill shows how much energy you used and the start and end dates. Divide one by the other. For example, 1,620 kWh over 90 days is 18 kWh a day.

Do this for a summer and a winter bill, because heating and cooling change your use a lot. Then use the result in our guide to what size solar system you need.

Usage charges and tariffs

Usage charges are in cents per kWh. How they’re worked out depends on your tariff type:

• Single rate: the same price at all times.
• Time-of-use: peak, shoulder and off-peak prices. Your bill shows when each applies.
• Controlled load: a separate, cheaper rate for appliances such as some hot water systems, on their own circuit.
• Demand: an extra charge based on your highest power draw at busy times.

The usage rate is what each kWh of your own solar saves you. Our guide to time-of-use tariffs explains when it pays to move appliances.

The supply charge

The supply charge is a fixed amount per day for being connected. Using less power, from solar or anywhere else, doesn’t reduce it. When a retailer estimates your savings, check they haven’t counted the supply charge.

Solar exports and feed-in credits

If you already have solar, your bill shows the kWh exported and the credit you earned. Divide exports by the days in the period. That daily surplus is the most a battery could shift, which is the starting point for working out whether a battery is worth it.

Actual or estimated reads

Your bill shows whether it’s based on an estimate of your usage. An estimate is corrected later, but don’t size a system from it. Use bills based on actual reads.

Your NMI

Your NMI is a unique number for the electricity connection at your address, not your meter number. It’s usually on the first page of your bill, near your customer details, and always has 10 or 11 characters. In Queensland it usually starts with two letters. It never contains the letters O or I, so if you see those, they’re zeros and ones.

Enter it on Energy Made Easy (or Victorian Energy Compare in Victoria) to compare plans using your last 12 months of real usage, instead of an average household.

The “better offer” message

Every three months, retailers must show a message under the heading “Could you save money on another plan?”. If it shows a cheaper plan, ask to switch, even if the plan name looks similar to yours.

This guide is general information, not financial or legal advice. Rules, rebates and prices change, so check the linked sources before you decide. Facts checked 18 October 2026.