At a glance
| Tool | Type | Price | Best for |
|---|---|---|---|
| Climate.OneBuilding.Org | Online repository | Free | The first place to look for a free, recent typical-year EPW for a weather station. |
| EnergyPlus weather data | Online library | Free | Downloading EPW, design-day and statistics files from the library maintained alongside EnergyPlus. |
| EPWmap | Web map, open source (MIT) | Free | Finding the nearest free EPW file on a map. |
| PVGIS | Web app and API | Free, no registration | A free typical-year EPW for any location, especially where there is no nearby weather station. |
| Oikolab | Web tool and API | Pay as you go at $0.01 per unit, with 1,500 free units a month; Business plan $150/month | Generating TMY or actual-year EPW files for any coordinates, including recent years. |
| NASA POWER | Web viewer and API | Free | Free actual-year EPW files for any coordinates, for model calibration or remote sites. |
| Meteonorm | Web app and API | From CHF 320/year (Basic); Pro CHF 980/year; Expert CHF 4,200/year; one-off datasets on request | Typical and actual years for any location, exported in the formats of many simulation tools. |
| DesignBuilder Climate Analytics | Web app | €895/year, including 150 download credits | Design-year, actual-year and future EPW files for many locations, with analysis tools to choose between them. |
| CBE Clima Tool | Web app, open source | Free | Viewing and analysing any EPW file in the browser for free. |
| C4B | Web app | Free plan for analysis; EPW downloads on the Technical and Enterprise plans (custom quote) | Analysing weather data for an address without handling files, and, on the Technical and Enterprise plans, building a custom site EPW. |
How to choose
First decide whether you need a typical year or an actual year. Typical meteorological years (TMY, TMYx, IWEC and similar) combine representative months from many years and are the usual input for design and energy simulation. An actual meteorological year (AMY) is one real year, which is what you need to calibrate a model against metered data.
Then look at the source. Station files, such as the TMYx files on Climate.OneBuilding.Org, come from measured records at airports and other weather stations, but the station may be far from your site or at a different altitude. Generated files come from reanalysis or satellite data on a grid (ERA5, MERRA-2, SARAH and others), so they exist for any coordinates, at resolutions from a few kilometres to about 100 km. Check which years each file is built from, because an older period may not reflect today's climate.
Cost and licence vary widely. Climate.OneBuilding.Org, the EnergyPlus library, PVGIS and NASA POWER are free; commercial services charge per file, per credit or data unit, or by monthly or yearly subscription, and usually add more locations, support or future-climate options.
Whatever the source, open the file in a viewer before you use it. Check the location, elevation and period in the header, and look for gaps or implausible values. For future-climate files, most tools start from one of the files below and morph it: see the future weather file tools guide.
Climate.OneBuilding.Org
The first place to look for a free, recent typical-year EPW for a weather station.
- 17,315 TMYx locations: typical years built from NOAA's Integrated Surface Database with the ISO 15927-4 method.
- The 2026 release adds TMYx files for 2011–2025, with solar radiation from ERA5 reanalysis (courtesy of Oikolab); the 2009–2023, 2007–2021 and 2004–2018 sets remain available.
- Each download includes EPW plus CLM, WEA, PVsyst, DDY design conditions and STAT files, and a RAIN file of hourly precipitation where the source data include it.
- Also hosts other national datasets, and future climate files for some countries, including Canada and Brazil.
EnergyPlus weather data
Downloading EPW, design-day and statistics files from the library maintained alongside EnergyPlus.
- Browse by region and country, search by keyword, or pick a station on a map.
- Each location offers EPW, DDY (design days) and STAT files.
- Its Weather Data for Simulation page lists other public and commercial sources of weather data.
EPWmap
Finding the nearest free EPW file on a map.
- One map of the free EPW files hosted by the EnergyPlus website and Climate.OneBuilding.Org.
- Built by the Ladybug Tools team as part of Pollination; Ladybug's EPWmap component opens the same map from Grasshopper.
Good to know
- The map's built-in file list dates from October 2023: the newest TMYx period it links to is 2007–2021, while Climate.OneBuilding.Org now also publishes 2009–2023 and 2011–2025 files.
PVGIS
A free typical-year EPW for any location, especially where there is no nearby weather station.
- The TMY tool builds a typical year for any location except the poles and downloads it as CSV, JSON or EPW.
- Solar radiation from PVGIS-SARAH3, PVGIS-NSRDB or PVGIS-ERA5 depending on the location, and other variables from ERA5 reanalysis.
- Available through the web interface and an API.
Good to know
- Built mainly for solar energy work. In PVGIS 5.3, a test TMY for Barcelona drew its months from 2005 to 2023.
Oikolab
Generating TMY or actual-year EPW files for any coordinates, including recent years.
- Downloads TMY or AMY EPW files for any location, from 1940 to the present.
- EPW files are generated on the fly from ERA5 reanalysis, so they are not limited to airport locations.
- Also serves hourly weather data as JSON, CSV or NetCDF through an API.
NASA POWER
Free actual-year EPW files for any coordinates, for model calibration or remote sites.
- The hourly API returns EPW files for its Sustainable Infrastructure (formerly Sustainable Buildings) community, for dates from 1 January 2001 to near real time.
- Meteorology from NASA's MERRA-2 model and solar data from the CERES and FLASHFlux projects.
- Radiation on a 1° grid and meteorology on a 0.5° by 0.625° grid, per its methodology documentation.
Good to know
- Grid cells are roughly 50 km (meteorology) to 100 km (solar radiation) across, so local effects of coasts, relief and cities are averaged out.
Meteonorm
Typical and actual years for any location, exported in the formats of many simulation tools.
- Curated data from 10,000 meteorological stations, 5 satellites and climate reanalysis.
- TMY and AMY files, extreme-scenario simulation, and future climate under SSP1-2.6, SSP2-4.5 and SSP3-7.0.
- Exports EPW, PVsyst, TMY3, WUFI, IDA ICE, PHPP10 and other formats.
DesignBuilder Climate Analytics
Design-year, actual-year and future EPW files for many locations, with analysis tools to choose between them.
- Data from over 43,000 weather stations, plus actual-year data from NASA's MERRA-2 reanalysis on a 0.5° by 0.625° grid.
- Downloads in EPW format; the licence's 150 credits cover up to 150 Design Year or 75 Actual Year files.
- Options for future climate projections and urban heat island adjustments.
CBE Clima Tool
Viewing and analysing any EPW file in the browser for free.
- Upload your own EPW, or pick one of more than 27,500 on its map.
- Temperature, humidity, sun, wind, psychrometric and outdoor comfort charts from the file.
- Exports charts as SVG and the file's data as CSV.
C4B
We make C4BAnalysing weather data for an address without handling files, and, on the Technical and Enterprise plans, building a custom site EPW.
- Every search finds the nearest OneBuilding.org weather file (usually TMYx) for an address and analyses it: there is nothing to download or upload.
- Projects on paid plans compile a typical year at the site's coordinates from Open-Meteo's blend of ERA5-Land, ERA5 and ECMWF IFS (about 9 to 25 km), CERRA (5.5 km, Europe) or NORA3 (3 km, northern Europe), corrected to the site's elevation.
- The Technical and Enterprise plans add a custom EPW builder: ERA5-Land or CERRA data, a 30-year, 15-year or custom window, the Sandia, TMYx (ISO 15927-4) or entropy method, and typical, hot, cold, seasonal-extreme and extreme-year presets.
Good to know
- EPW downloads, including site-specific and future files, are only available on the Technical and Enterprise plans; other plans use the data inside C4B's analyses.
- C4B works from a location: it does not analyse EPW files that you upload.
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Frequently asked questions
Where can I download EPW weather files for free?
Climate.OneBuilding.Org publishes free TMYx files for more than 17,000 locations, and the EnergyPlus website has its own free library. Ladybug Tools' EPWmap shows free files on a map. Where there is no station nearby, PVGIS generates a free typical-year EPW for any location except the poles, and NASA POWER provides free actual-year EPWs from 2001 onwards.
What is the difference between TMY, TMYx and AMY files?
A TMY (typical meteorological year) combines, for each calendar month, a representative month from a long record into one year. TMYx is the name Climate.OneBuilding.Org uses for its typical years built from NOAA Integrated Surface Database station records with the ISO 15927-4 method, either from a station's full record or from recent 15-year periods such as 2011–2025. An AMY (actual meteorological year) is a single real year, used for example to calibrate an energy model against metered data.
Can I create an EPW file for a location without a weather station?
Yes. Services that work from gridded reanalysis or satellite data, such as PVGIS, Oikolab, NASA POWER, Meteonorm and DesignBuilder Climate Analytics, produce EPW files for any coordinates. Check the grid resolution and the years each file is built from.
How do I open or view an EPW file?
An EPW is a plain-text, comma-separated file, so a text editor or spreadsheet can open it, but a viewer is much easier to read. CBE Clima Tool analyses an uploaded EPW in the browser, EPW Insights analyses one locally in the browser without uploading it, Andrew Marsh's Weather Data app shows it as a 3D chart, and Ladybug Tools imports it into Grasshopper.
Can I download EPW files from C4B?
Only on the Technical and Enterprise plans, which add a custom EPW builder and downloads of site-specific and future files. On the Free, Essential and Teams plans, C4B uses the weather data inside its own analyses.
Sources
We make C4B. Information about the other tools comes from their official websites and documentation, checked on 18 September 2026. Products and prices change, so check each vendor's site for the latest details. All product names belong to their respective owners.
- Climate.OneBuilding.Org
- EnergyPlus: Weather Data
- EnergyPlus: Weather Data for Simulation
- Ladybug Tools EPWmap
- EPWmap source code and README
- Ladybug Tools primer: EPWmap component
- Ladybug Tools primer: component index
- PVGIS (European Commission Joint Research Centre)
- PVGIS: typical meteorological year (TMY) generator
- Oikolab: product and pricing
- Oikolab documentation: API references
- NASA POWER: hourly API and formats
- NASA POWER: methodology and data sources
- NASA POWER: Data Access Viewer quick start
- NASA POWER: user communities
- Meteonorm web application and plans
- DesignBuilder Climate Analytics
- DesignBuilder Climate Analytics licence
- CBE Clima Tool documentation: overview
- CBE Clima Tool documentation: main features
- CBE Clima Tool documentation: tabs explained
- EPW Insights source code and README
- Andrew Marsh: Weather Data web app
Related on C4B
Site-specific weather data
A typical-year weather file compiled from reanalysis at the project's coordinates, alongside the nearest station.
Future climate scenarios
Future weather files for any year up to 2100 under five SSP scenarios, overlaid on the project's analyses.
Site climate analysis
A full climate study for any location in the world, run in the browser from a single address or map pin.
C4B vs Meteonorm
Meteonorm supplies climate data files for many simulation tools; C4B turns a site's climate into design analyses and a report.
C4B vs DesignBuilder Climate Analytics
Climate Analytics prepares weather files for energy modelling; C4B turns site climate into early design analyses and a report.
C4B vs CBE Clima Tool
Both run in the browser. Clima is free and analyses EPW files; C4B works from any address and adds future climate, energy and PDF reports.
C4B vs Ladybug Tools
Ladybug is a free, flexible Grasshopper toolkit; C4B is a ready-made browser workflow from an address to a climate report.