At a glance
| Tool | Type | Price | Best for |
|---|---|---|---|
| Global Wind Atlas | Web map and energy yield calculator | Free | Checking the mean wind speed at a location and height against a consistent global dataset, before any turbine is chosen. |
| System Advisor Model (SAM) | Desktop app (Windows, macOS, Linux) | Free; registration gives a free software key | Hourly energy and project economics for one small turbine or several, from a wind data file or a Weibull distribution. |
| ICC-SWCC certified small turbines | Online directory of certified turbine ratings | Free to consult | Comparing the certified ratings of small turbines; a directory, not a yield calculator for your site. |
| C4B | Web app, in the browser | Free plan; paid plans from €59/month (cancellation takes effect after 12 billing cycles) or €599/year, with a 7-day free trial | A first estimate at concept stage of what a small wind turbine on a roof or on the ground could produce at an address, by turbine type and hub height. |
| UrbaWind | CFD software for urban wind | Price on request (quote and demo through Meteodyn's contact form) | Placing small turbines on and between buildings with a 3D simulation of the wind around the real urban geometry. |
| Windographer | Software for wind data analysis | Subscription only; price on request | Turning wind measured on the roof or site into annual energy for candidate turbines. |
| WAsP | Software | WAsP Bundle €2,100 the first year, then €800 per year | Wind resource and energy yield at a specific site from measured or modelled wind, with terrain, land cover and nearby sheltering obstacles. |
| windPRO | Modular software for wind project design | BASIS, PARK and LOSS & UNCERTAINTY listed at €1,700 from 1 January 2026, excluding VAT | Detailed energy yield studies with a structured loss and uncertainty analysis, as wind project developers prepare them. |
How to choose
Be clear about the question. At concept stage an architect or engineer usually wants to know whether small wind is worth considering at all, which kind of turbine and how high it would have to stand. A developer buying a turbine needs a measured, defensible yield. Desktop tools answer the first; the second needs wind measured at the site. Wind in cities is weak and turbulent, so treat any desktop figure for a roof as a screening estimate.
Look at where the wind comes from. Weather-station files record the wind at 10 m over open ground, usually at an airport; wind atlases and reanalysis grids describe terrain and land cover over hundreds of metres to kilometres. Neither sees the building next door. Lifting that wind to hub height over a rough urban surface is the largest single step in any estimate, and a CFD model of the real buildings or a few months of measurements on the roof are the usual ways to see the local flow.
Check the output. A single annual figure hides how uncertain it is: P50 is the median year and P90 the figure nine years in ten should beat, and the gap between them is widest on urban sites. Energy against hub height shows whether a taller mast is worth it. To compare turbines, certified ratings at a common reference wind are easier to compare than datasheet claims.
Read the model's assumptions. Power curves are either measured or synthesised from a few datasheet values; turbulence, losses, air density and wakes between turbines may be modelled or left out. Wind-farm tools such as WAsP and windPRO are built for wind resource and yield studies over terrain and land cover; on a roof, where the flow separates and recirculates, CFD or on-site measurement adds the most.
Global Wind Atlas
Checking the mean wind speed at a location and height against a consistent global dataset, before any turbine is chosen.
- A free, web-based application for identifying high-wind areas and making preliminary calculations, virtually anywhere in the world.
- Wind resource maps on a grid of about 250 m at 10, 50, 100, 150 and 200 m above ground; version 4.0 computes them with DTU's PyWAsP microscale model.
- An energy yield calculator gives annual energy production, capacity factor or full load hours for a generic or custom turbine power curve, as downloadable GIS data.
Good to know
- Terrain is described at about 30 m (elevation) and 50 m (roughness from land-cover data), not building by building; the release notes describe the gross capacity factor layers as for 3.45 MW turbines at 100 m hub height.
System Advisor Model (SAM)
Hourly energy and project economics for one small turbine or several, from a wind data file or a Weibull distribution.
- Simulates one or more large or small turbines over a year in hourly steps, from an SRW wind time series or a Weibull distribution of the wind resource.
- Turbine performance from the turbine library's power curves or from design parameters, with hub height, a shear coefficient, wake models and loss factors.
- Residential and commercial financial models for turbines that supply a building behind the meter.
Good to know
- Without data at several heights, SAM scales the wind to hub height with a power-law shear coefficient (from 50 m for a Weibull input), so the result follows the file and the coefficient you give it.
- NREL was renamed the National Laboratory of the Rockies in December 2025; SAM is now at sam.nlr.gov.
ICC-SWCC certified small turbines
Comparing the certified ratings of small turbines; a directory, not a yield calculator for your site.
- Lists each certified turbine's annual energy production, sound level, rated and peak power, status and expiry date, with its label, certificate and summary report.
- The rated annual energy is the energy calculated for one year at an average wind speed of 5 m/s (11.2 mph), so turbines are compared on one basis.
- Certifications follow ACP 101-1 (2021) or the earlier AWEA 9.1 (2009) standard.
Good to know
- A short list of certified turbines (eight when checked), and the 5 m/s rating is a common reference, not the wind at your site. Check each turbine's certification status and expiry date.
C4B
We make C4BA first estimate at concept stage of what a small wind turbine on a roof or on the ground could produce at an address, by turbine type and hub height.
- Hourly energy from the site's typical-year weather file: 10 m wind lifted to hub height for open, suburban or urban terrain, corrected for air density and turbulence, then reduced by losses.
- Results as P50 and P90, with an uncertainty band that widens with the terrain: on an urban site P90 is about 0.54 times P50.
- Four turbine types (tulip, modular and H-rotor vertical-axis, Archimedes-screw horizontal-axis) from a catalogue of 19 manufacturer models, checked against the Betz limit, survival wind speed and rooftop recirculation.
- Paid plans add comparison across types and sizes, energy against hub height, the ranked catalogue and site-specific weather data; the Technical and Enterprise plans open every parameter, including custom turbines.
Good to know
- Works from a weather-station or reanalysis file, not a measured or CFD study of the roof: shelter from neighbouring buildings, roof-edge speed-up and exact placement are not modelled, so plan around P90 and measure the wind on site for at least three months before buying.
- Mounting options follow the manufacturers' datasheets and are not a structural, acoustic or permitting review; the catalogue is ranked by annual energy only, not by cost, noise or weight.
UrbaWind
Placing small turbines on and between buildings with a 3D simulation of the wind around the real urban geometry.
- Computes local urban wind and 3D airflow among buildings and vegetation, solving the RANS equations, with automatic meshing refined to 50 cm near buildings, the ground and result points.
- A small wind turbines module covers wind resource assessment, potential annual energy production and optimisation of turbine positions; other modules cover pedestrian wind and thermal comfort and natural ventilation.
- Imports 3D models as STL and wind data as time series or statistics in Météo-France, EnergyPlus or Meteonorm formats, and exports CSV and TXT results.
Windographer
Turning wind measured on the roof or site into annual energy for candidate turbines.
- Imports wind data from met towers, sodar or lidar in virtually any format, with quality-control flags and filters.
- Long-term adjustment by measure-correlate-predict (MCP) against reference data, including free ERA5 and MERRA-2 data, and vertical extrapolation with shear and turbulence analysis.
- The Wind Turbine Output window compares turbine models at each time step of the data, adjusting for air density and applying losses, and reports annual energy production and net capacity factor.
- Exports to wind flow models including WAsP, WindFarmer, WindSim and Meteodyn WT.
Good to know
- It works on measured wind data, so it needs a measurement campaign at the site.
WAsP
Wind resource and energy yield at a specific site from measured or modelled wind, with terrain, land cover and nearby sheltering obstacles.
- DTU describes it as industry-standard software for wind resource assessment, siting and energy yield calculations.
- Uses wind climate data from a nearby mast or from mesoscale modelling, elevation, land cover and nearby sheltering obstacles, with an obstacle model for the wind close to them.
- Can import wind climates and vector maps from the Global Wind Atlas for preliminary analyses; the bundle also includes WAsP Engineering and the Windfarm Assessment Tool.
Good to know
- Its built-in IBZ flow model is most suitable for flat to moderately complex terrain; DTU points to WAsP CFD for steep terrain and to WAsP Engineering for a full IEC site assessment.
windPRO
Detailed energy yield studies with a structured loss and uncertainty analysis, as wind project developers prepare them.
- BASIS is the backbone of the modules, PARK calculates annual energy including wake losses, METEO imports and screens wind measurements, and MODEL interfaces with WAsP and CFD models.
- LOSS & UNCERTAINTY works with a PARK calculation and gives annual production at exceedance levels between P50 and P99, with power curve uncertainty following IEC 61400-12.
- More than 1,000 wind turbine models, and modules for noise, shadow flicker and visual impact.
Good to know
- An uncertainty study combines BASIS, PARK and LOSS & UNCERTAINTY, which EMD lists as separate modules.
See your site's climate before design begins
Pin any location and get climate, comfort and preliminary energy insight your whole team can read. Start with a 7-day free trial, or book a 30-minute demo.
Free plan; paid plans from €59/month (cancellation takes effect after 12 billing cycles) or €599/year, with a 7-day free trial. No card required. If you add a card during the trial, the plan is charged when the trial ends; otherwise your account moves to the Free plan. See all plans.
Frequently asked questions
How much energy does a small wind turbine on a building produce?
It can be much less than its datasheet suggests. Wind on a roof is slower and more turbulent than at the open-ground station where weather files are recorded, and energy follows roughly the cube of wind speed. Compare turbines on certified ratings, such as the ICC-SWCC rated annual energy at an average 5 m/s, then estimate the site with a range (P50 and P90) rather than a single figure.
What do P50 and P90 mean for a wind turbine?
P50 is the median annual energy: half of years should produce more and half less. P90 is the figure that nine years in ten should beat, the one to plan around when the scheme has to work in a poor wind year or when nobody has measured the wind at the site. windPRO's LOSS & UNCERTAINTY module reports exceedance levels from P50 to P99; C4B shows P50 and P90, with a band that widens on urban sites.
How much does hub height matter?
A great deal. Wind gains speed with height, fastest near the ground, and energy grows with roughly the cube of speed, so 10% more wind gives about 33% more energy. On a roof the rotor also has to clear the turbulent zone the building creates. Tools that plot energy against hub height, such as C4B on paid plans, show where extra mast height stops paying back.
Can I use the Global Wind Atlas for a rooftop turbine?
As a cross-check, yes. It gives the mean wind speed at 10 to 200 m on a grid of about 250 m, with terrain described by elevation and land cover, so it does not see individual buildings. Compare its mean wind speed at your hub height with the figure your yield tool uses before trusting the result.
When do I need another tool alongside C4B?
When the decision depends on the flow around the roof or on measured wind. C4B estimates P50 and P90 from the site's weather file, and its technical view opens every parameter, from the wind profile and losses to custom turbines and groups of turbines. It does not model shelter from neighbouring buildings, roof-edge speed-up or exact placement, which a CFD tool such as UrbaWind resolves, and no desktop estimate replaces measurement: before buying, measure the wind on site for at least three months (and analyse it with software such as Windographer or SAM), use certified ratings where they exist, and have the structure, noise and permits reviewed.
What wind data does C4B use?
Two sources, both at 10 m. Weather station data are EPW files from climate.onebuilding.org, built from NOAA's global ISD archive: each hour holds the station's observation as its national service reports it, the mean of the 10 minutes before the observation (the WMO standard) or of the last 2 minutes at US stations, and hours with no report are interpolated or filled with ERA5 data. Site-specific data are hourly reanalysis values (ERA5, ECMWF IFS, CERRA or NORA3, depending on location and period): an instantaneous model value for a grid cell about 3 to 31 km wide, which smooths local effects and tends to underestimate strong winds and gusts. Neither is a gust or a structural design wind speed: for structural design use the local code, such as ASCE 7 (3-second gust, from the ASCE Hazard Tool) in the US, or EN 1991-1-4 with its National Annex, or CTE DB SE-AE, in Europe and Spain.
Sources
We make C4B. Information about the other tools comes from their official websites and documentation, checked on 9 October 2026. Products and prices change, so check each vendor's site for the latest details. All product names belong to their respective owners.
- Global Wind Atlas: home page
- Global Wind Atlas: key features
- Global Wind Atlas: introduction
- Global Wind Atlas: FAQ
- Global Wind Atlas: release notes
- SAM: home page
- SAM: download
- SAM: wind power
- SAM help: wind power model
- NLR: Energy Department renames NREL
- ICC-SWCC: certified small turbines
- Meteodyn: UrbaWind
- UL Solutions: Windographer
- Windographer help: Wind Turbine Output window
- DTU: WAsP
- DTU: WAsP prices
- EMD International: windPRO
- EMD International: windPRO modules
- EMD International: windPRO LOSS & UNCERTAINTY
- EMD International: price adjustments for windPRO (2026)
- WMO: Guide to Instruments and Methods of Observation (WMO-No. 8), Volume I, Chapter 5, surface wind
- ICAMS (formerly OFCM): Federal Meteorological Handbook No. 1, Surface Weather Observations and Reports (FCM-H1-2019), section 5.4.3
- Minola et al. (2020), Near-surface mean and gust wind speeds in ERA5 across Sweden, Climate Dynamics
- Baas (2026), Systematic under-representation of ERA5 10 m wind speeds in the ERA5-Land product undermines wind energy studies, Applied Energy 412, 127634
- ASCE Hazard Tool: design wind speeds to ASCE 7
- Código Técnico de la Edificación: DB SE-AE, Acciones en la edificación (wind, Annex D)