Small wind is real technology - on the right site. The physics is unforgiving: power scales with the cube of wind speed, so a site with 4 m/s average makes roughly half the energy of one at 5 m/s. Urban rooftops, surrounded by buildings, are turbulent and slow.
Rule of thumb: if trees around you aren't constantly swaying, a terrace turbine will disappoint. Genuinely windy open sites - farmhouses, ridge lines, coastal strips - can work, ideally after a month of actual wind logging.
Our advice, and we say this running a green directory: in most NCR colonies, put the same money into more solar. Where wind is marginal, a small solar-wind hybrid at least diversifies. Use the feasibility tool before any purchase.