Weather Data

Which weather format does Sefaira use?

Sefaira uses the EnergyPlus Weather file format, which is indicated by the file extension .epw

How is the .epw weather format related to TMY2/TMY3/IWEC/RMY and other weather file formats?

The .epw format was developed by the US Department of Energy to be a standard weather data format, to which several other data formats could be converted. The DoE provides a collection of thousands of weather files from around the world on their website ( which are derived from a wide range of sources and formats.

A list of these sources, which includes TMY2, TMY3, IWEC, and RMY, is available at

What does the .epw weather file contain?

The .epw weather file contains weather data for all 8760 hours of a 365-day year. These data include

  • Location information
  • Temperature, humidity and enthalpy
  • Wind data
  • Solar radiation data

In the Sefaira web application, do the design conditions for sizing depend on the weather file?

Yes, Sefaira creates cooling and heating design days from the weather file for each project based on guidelines in the ASHRAE 90.1 standard.

What should I do if the weather file I need for my project is not available in Sefaira's list of locations?

For a complete list of weather locations available, go to If your desired location is not in this list, please send us a message at We periodically upload new locations to our database and will add the requested location in our next upload.

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