A quick summary, not the full technical detail — see
ARCHITECTURE.md
on GitHub for that.
Solar installs
Region figures — installs, capacity, homes/business and % of connections — are EMI's own published numbers (the Electricity Authority), exact.
Streets come from EMI's street-level file, matched to OpenStreetMap roads. Streets with three or fewer installs are published as “3 or less” for privacy, shown here as 1–3.
Town and district counts (marked “~”) are added up from those streets, counting each “3 or less” street at its region's measured average, so each region's streets add up to EMI's exact total.
Town and district % (marked “est”) is modelled: 2023 Census dwellings projected forward, scaled up to all connections using the region's mix. EMI publishes no connection total that fine.
Batteries are EMI figures, published by region only — towns show their region's rate.
Farms are a range between two estimates, since EMI publishes no farm split (hover the figure for how each is made).
Electric vehicles
Counts by district from NZTA's Motor Vehicle Register, not modelled. “% of the fleet” is electric vehicles as a share of all registered vehicles in that district, excluding trailers and caravans.
Vehicle Details lists the most common electric and fossil-fuelled models (petrol, diesel, hybrid, plug-in hybrid) by region and district.
Keeping it current
Refreshes automatically every week. EMI and NZTA publish on their own schedules (EMI's street data currently updates about weekly, NZTA's register about monthly); “Updated” shows each source's own release date.