Your electricity bill usually combines your usage in kilowatt-hours (kWh), a daily supply charge, and any discounts, fees or credits. Usage is calculated by multiplying the energy you used by your retailer’s tariff, which may vary by time of day, season or plan; GST is generally included. Check the billing period, meter readings and whether the reading is actual or estimated, as estimates can affect the amount due. If the bill seems wrong, contact your retailer first and ask for a bill explanation or meter check.