# Solarific

> Free reference data for solar panel placement: the most efficient tilt and
> orientation for more than 70,000 cities worldwide, worked out from each
> city's latitude. All data is CC0 (public domain); cite or reuse it freely.

Key facts:

- Every city page gives the best fixed tilt, the direction to face, 2-season
  and 4-season tilts, a 12-month adjustment table with the noon sun angle, and
  today's exact angle.
- URLs follow /{country}/{state}/{city}, all lowercase and slugged, for
  example https://solarific.co/us/co/denver and
  https://solarific.co/pk/punjab/lahore. The United Kingdom is `uk`, not `gb`,
  and the state segment is a slugged region name rather than a short code
  (https://solarific.co/uk/london-city-of/london). Build city URLs from the
  `url` column in the dataset rather than guessing them.
- The fixed-tilt figure comes from a quadratic in latitude calibrated against
  PVGIS v5.2 optimal-slope data for 52 cities spanning 1 to 69 degrees of
  latitude: tilt = (-0.007 * lat^2) + (1.127 * lat) + 3.27, accurate to 3.4
  degrees RMSE against that reference. Monthly and daily angles use the
  subsolar-point declination model.
- Southern-hemisphere cities face north; northern-hemisphere cities face south.
- The whole dataset is downloadable as one CSV or JSON file. No key, no
  sign-up, no rate limit.

## Data

- [Dataset](https://solarific.co/data): what the columns mean and how to cite it
- [cities.csv](https://solarific.co/data/cities.csv): every city, one row each,
  with fixed, 2-season, 4-season and 12-month tilts
- [cities.json](https://solarific.co/data/cities.json): the same data with the
  monthly figures nested
- [Methodology](https://solarific.co/methodology): the formula, its accuracy
  against PVGIS, and where it stops working

## Pages

- [Best solar panel angle](https://solarific.co/best-solar-panel-angle): the
  latitude-to-tilt reference table and seasonal rules
- [RV solar panel angle](https://solarific.co/rv-solar-panel-angle): what
  tilting gains over lying flat, by latitude and season
- [Campervan solar wattage](https://solarific.co/campervan-solar-wattage):
  sizing method with a typical-loads table
- [Portable solar panel angle](https://solarific.co/portable-solar-panel-angle):
  aiming and tilting portable panels at camp
- [All countries](https://solarific.co/countries): the entry point to every
  state and city page
- [How solar power works](https://solarific.co/how-does-solar-power-work): a
  plain-English explainer
- [Embeddable widget](https://solarific.co/widget): a live angle widget any
  site can embed

## Optional

- [llms-full.txt](https://solarific.co/llms-full.txt): the formulas, the
  latitude reference table, and the licence terms in one file
- [Sitemap](https://solarific.co/sitemap)