Urban wind powered systems are designed to be mounted on the top of roofs or on walls, and some manufacturers are claiming that they can meet around 30% of the electricity needs of many households.
Unfortunately, these claims are, to say the least, grossly exaggerated. Do not confuse urban wind systems with small tower-mounted wind electric systems. These ones are designed to respond to residential eletricity need, or to meet farm and business power needs. Their capacity and the height of the their towers make them very different devices. And the reasons are rather obvious: urban wind turbulence, low urban wind speeds and restrictions on the height or placement of the towers.
Do not expect too much from urban wind systems. Except in some exceptional conditions, they will not provide significant amounts of power; some small systems may be useful to power home devices, and just that.
There are dozens of new wind powered products being sold in specialty stores, designed for urban settings. They are mostly intended for small applications, particularly battery charging.
Building-mounted turbine systems have a lower output than tower-mounted turbines; their electrical output is often around 1 kW - 2 kW... But their role is marginal.
The wind speed in urban sites is too low, and its patterns too inconsistent; there is popular opposition to tall towers; and the products being offered are not able to overcome these obstacles.
It’s possible to devise lightweight structures without the inconveniences of small wind systems used in rural areas: without their tall towers, without a negative impact on the structures of the building they are mounted on, and without producing noise. But that’s not in the foreseeable future.
You can buy renewable energy from utilities in many countries - US, Canada, UK, Australia… - or help the green producers by buying "certificates". See: Buying Renewable Energy.
The best alternatives
There are some good alternatives to urban wind systems, if you want to help the environment.
You can buy green electricity, coming from big wind farms. Wind electricity is already competitive with the electricity coming from fossil fuels and you will not have to pay significantly more (see Box).
And you can also invest in home energy efficiency: from an environmental standpoint reducing electricity consumption is at least as important as producing green power. It may not sound that enthralling, but energy conservation measures - high levels of home insulation, energy-efficient windows, energy efficient appliances and lighting - are as important to help the environment as producing green electricity through small wind systems, or other renewable source of energy.Untested products
Many urban wind systems are rather experimental and insufficiently tested products.