There is no standard size. The right array depends on how much electricity the property uses, when it uses it, what the roof can carry and what you want the system to achieve.
Start with usage
Your power bill shows consumption in kWh. A year of bills, or interval data from your retailer, shows how that use changes between summer and winter and between day and night. That pattern matters as much as the total.
Then generation
Each kilowatt of panels in New Zealand produces a different amount of energy across a year depending on region, orientation, pitch and shading. North-facing, unshaded arrays produce the most. Winter output is a fraction of summer output everywhere in the country.
Then the goal
- Lowest upfront cost, match daytime use
- Most self-supply, size for daytime use plus storage
- Future loads, allow for an EV, heat pump or electric hot water
- Backup, size storage and power for essential circuits
Then the constraints
Usable roof area, the inverter's rating, the switchboard and the export limits on your connection can all cap the practical size. An oversized array that cannot export, or that the inverter clips every sunny afternoon, is roof space without value.
Online estimates, including the configurator on this site, are a starting point. Final system sizing requires a site and electrical assessment.
