Wind power variations at two heights (the surface level and turbine hub level) were investigated at 20 locations in the shelf seas of India using hourly fifth generation European Centre for Medium-Range Weather Forecasts (ECMWF) atmospheric reanalyses of the global climate (ERA5) data covering the last 40 years (1979 to 2018). The interannual and seasonal variability in wind power was studied. The wind power density, the exceedance probability of power density and the exploitable wind resources were examined. In the Indian shelf seas, the annual mean wind power density at 10 m above mean sea level varies from 82 to 353 W/m2. Wind power density at 110.8 m is 20% to 40% higher than at 10 m above mean sea level. The study shows that the shelf seas have an abundance of wind power, with wind speeds over 3 m/s during 90% of the time at locations 1 to 3, 12 and 13, with a high occurrence of exploitable wind energy above 0.7 × 103 kWh/m2. Among the locations studied, the most power-rich area was location 12, where during ~62% of the time power was greater than 200 W/m2. A significant change (~10–35%) in inter-annual wind power density was detected at a few locations, and these variations were associated with Indian summer monsoon and El Niño–Southern Oscillation events. Trend analysis suggests a decreasing trend in the annual mean wind power density for most of the locations in the Indian shelf seas over the last 40 years. Wind power has considerable directional distribution, and at different locations the annual wind power from the dominant direction is 10% to 79% of the total available power from all directions.