SoLax: Solar Roof Planner

See how many solar panels fit on your roof, and what they'd produce, without leaving the browser. Find your house on a satellite map of the Philippines, click its roof (or trace it yourself), and the app lays out 550 W panels on the real roof outline, sizes a system for your electric bill and estimates production month by month.

Features

• Pick your roof on a satellite map. Building outlines from OpenStreetMap light up as you hover.
• Draw or adjust the outline. Trace a roof that isn't mapped, or drag the corners of one that's off.
• Real panel layout. Panels (2 m × 1 m, 550 W) are fitted in PostGIS to the roof's shape and direction, with a 0.5 m clear edge, in true metres (local UTM zone).
• Local sun data. Monthly production from NREL PVWatts v8 for the roof's exact location.
• Sized to your bill. Enter your monthly kWh; the app recommends just enough panels and shows what the whole roof could produce. Change the kWh and everything updates instantly.
• Accounts and saved plans. Register, save plans, reopen them on the map later (Supabase Auth).

Tech stack

Layer	Technology
App	Next.js 16 (App Router, TypeScript), React 19
Database	Supabase PostgreSQL + PostGIS, via Prisma 7 (@prisma/adapter-pg)
Auth	Supabase Auth (@supabase/ssr)
Map	Google Maps JavaScript API (satellite view)
Building outlines	OpenStreetMap via OpenFreeMap vector tiles, with the Overpass API as fallback; cached in the database
Solar estimates	NREL PVWatts v8

Getting started

Prerequisites

• Node.js 20+
• A Supabase project (free tier is fine)
• A Google Cloud project with the Maps JavaScript API enabled and billing linked (Google requires billing even within the free monthly allowance)
• An NREL API key: free at https://developer.nlr.gov/signup/ (NREL's APIs moved from developer.nrel.gov to developer.nlr.gov)

Setup

git clone https://github.com/AaronPublic/SoLax.git
cd SoLax
npm install            # also runs `prisma generate`
cp .env.example .env   # then fill in the values (see below)
npm run db:migrate     # enables PostGIS, creates the tables, turns on row-level security
npm run dev            # http://localhost:3000

If npm reports blocked install scripts, run npm approve-scripts --allow-scripts-pending, then npx prisma generate.

Environment variables

All settings live in .env, which is git-ignored. Never commit it. .env.example documents every variable.

Variable	Where it's used	Notes
DATABASE_URL	Server	Supabase transaction pooler URL (port 6543, ?pgbouncer=true)
DIRECT_URL	Prisma CLI	Supabase session/direct URL (port 5432), used for migrations
NREL_API_KEY	Server	PVWatts key. DEMO_KEY works for quick tests but is heavily rate-limited
NEXT_PUBLIC_GOOGLE_MAPS_API_KEY	Browser	Public by design. Restrict it by HTTP referrer in Google Cloud
NEXT_PUBLIC_SUPABASE_URL	Browser + server	Your project URL
NEXT_PUBLIC_SUPABASE_PUBLISHABLE_KEY	Browser + server	The publishable/anon key, never the secret/service-role key
NEXT_PUBLIC_MAP_BOUNDS, NEXT_PUBLIC_MAP_CENTER	Browser	Optional; default to the whole Philippines / Manila
OVERPASS_URLS	Server	Optional comma-separated Overpass servers for the fallback

If your database password contains special characters (@ # / ?), URL-encode them in both URLs.

Supabase Auth settings

In the Supabase dashboard:

1. Authentication → URL Configuration: set Site URL to your app's URL (http://localhost:3000 in development) and add http://localhost:3000/** (and your production URL) to Redirect URLs, so confirmation emails return to /auth/callback.
2. Supabase's built-in email sender only sends a few emails per hour. For development you can turn off Authentication → Sign In / Providers → Email → Confirm email; for production, configure your own SMTP.

How it works

1. Buildings. The browser asks /api/buildings for outlines in ~550 m tiles. The server serves them from the BuildingTile cache, or reads OpenFreeMap's z14 vector tiles (falling back to Overpass), splits them into individual roofs and caches them.
2. Panel fitting (lib/panel-fit.ts). One PostGIS query projects the roof to its UTM zone, finds its long axis (ST_OrientedEnvelope), removes a 0.5 m setback, tries 8 candidate grids (2 panel orientations × 4 half-step offsets), keeps panels fully inside the roof (ST_CoveredBy) and returns them sorted from the centre out.
3. Production. PVWatts is called once for a 1 kWp system (15° tilt, facing the equator, 14% losses). Output scales linearly, so lib/sizing.ts sizes any system from that profile, on the server and instantly in the browser.
4. Saving. POST /api/plans recomputes the plan on the server (it never trusts numbers from the browser) and stores it with the roof outline.

API

Method & path	Auth	Purpose
GET /api/buildings?tiles=<ix>_<iy>,…	—	Building outlines for map tiles
POST /api/calculate-solar	—	Fit panels and estimate production for a roof
POST /api/plans	Required	Save a plan (recomputed server-side)
GET /api/plans/:id	Owner	Open a saved plan
DELETE /api/plans/:id	Owner	Delete a saved plan

POST /api/calculate-solar body:

{ "geometry": { "type": "Polygon", "coordinates": [[[121.07, 14.65], "…"]] }, "monthlyKwh": 450 }

The response shape is CalculateSolarResponse in lib/types.ts. Roofs larger than 5,000 m², with more than 500 vertices, or outside the Philippines are rejected.

This is the beginning of the README. Read the rest at the original. Read the full README ↗