Where this data comes from

A quick summary, not the full technical detail — see ARCHITECTURE.md on GitHub for that.

Solar installs

• Real counts from EMI (the Electricity Authority), published monthly by street.
• Street positions are matched to real OpenStreetMap roads — about 97% match; the rest are mostly private lanes, rural roads, or recent renames.
• Region % is a real EMI figure (they publish both solar count and total connections at that level).
• Town % is an estimate, always marked "est" — EMI doesn't publish a real total that fine, so it's modelled from real Census dwelling growth instead.
• Battery counts are real EMI figures, but only published at region level — town popups show their region's rate, not a town-specific count.

Electric vehicles

• From NZTA's live vehicle register — a real join (electric count vs total local fleet), not modelled, down to district level.

Keeping it current

• Refreshes automatically every week. EMI and NZTA publish monthly, so it's never more than a few weeks stale.