The base data for this tool is 12 months of hourly domestic power consumption which includes charging two EV cars. Solar generation for a 6.3 kW system was calculated from NIWA data accounting for cloudiness, and roof tilt and direction.
The modelled system is used to compare power plan scenarios against a base system pulling all power from the grid. Options allow for no batteries, batteries, EV charging, and EV charging and V2L.
Three scenarios are modelled on top of a set baseline:
- The baseline is a current grid buy system that offers free evening power which is used to charge EVs (about 90% of need)
- Scenario 1 is Just adding a solar system but not changing behaviour
- Scenario 2 changes EV charging to daytime instead of nighttime
- Scenario 3 charges EVs during the day + uses their 3.6 kW V2L capability to help run the house.
Three power plans can be compared, including the current baseline and two alternatives. The calculator allows for flat rate, free or off-peak periods. At this stage, each plan can be only one option with one time period for off-peak or free.
Download Solar Power Plan Calculator User Guide
DISCLAIMER:
This is a personal project stimulated when trying to compare power plans and solar investment returns. It uses actual domestic data for 2025-2026 but, while care has been taken to check calculations, it is not to be relied upon. We take no responsibility for any actions or decisions users may take based on the outputs from this tool. If you find errors or have ideas, contact us and we may be able to develop further.
