Use an account-specific offer
Your distribution area, meter configuration and plan can affect the prices available. Copy the daily charge and each usage rate from the written offer rather than assuming one national retail price. The Electricity Authority provides a starting point for plan comparison.
Treat free hours as a load-shape question
The value of a free or discounted period depends on how much electricity the household uses in that period and what it pays during the remaining hours. Enter measured period shares where possible and test how the result changes if less use can be moved.
Read the whole contract
A bundle, prompt-payment condition, sign-up credit or controlled-load arrangement can change the comparison. Confirm tax inclusion and separate one-time benefits from recurring charges. The manual bill analyzer accepts NZD figures; the source guide does not represent a complete retailer feed.