Find the nearest cool public place and get heatwave alerts
Beginner8h1–2
LeafletWeather APINext.js
17/20Rainwater Harvesting Calculator
Estimate how much rainwater your roof can collect and what tank to buy.
Beginner8h1–2 people17/20 fit
Build Rainwater Harvesting Calculator for homeowners and schools in ~8h with 1–2 people. Stack: Leaflet + Next.js + Charts.
Why it wins: Quick calculator with local relevance.
Build flow
01 · Problem
People skip rainwater harvesting because they cannot estimate its value.
02 · Solution
Use roof area, local rainfall history and usage to compute harvestable volume, tank size and water bill savings.
03 · Build
- 1Add a polygon tool for roof area
- 2Fetch rainfall averages
- 3Compute volume
- 4Chart monthly capture
04 · Demo
Draw a roof on a map and show litres per year.
MVP checklist
- Roof area drawing
- Rainfall data
- Tank sizing
- Savings estimate
Tech stack
| Tech | Role | |
|---|---|---|
| Leaflet | Interactive maps | UI |
| Next.js | Frontend + API routes | Web |
| Charts | Data visualisation | UI |
Reference repos
Open-source projects you can build on. Links checked 2026-10-31.
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