Rooftop wind turbines offer a relatively inexpensive way to participate in the rush to renewable energy. The principle allure is low installation cost. Typically, tower installations for larger turbines add 50-80% to the cost of the system. With a rooftop turbine, an $800 tower is replaced by a $39 roof mounted tripod, or a length of pipe attached to the side of the house.

According to Ron Stimmel of the American Wind Energy Association, “…rooftop turbines still account for only 1 percent or so of the 10,000 small wind turbines that are sold each year in the country.” For this reason, few performance statistics are available from actual owners.

It’s possible, however, to get an idea of the estimated power output of a rooftop turbine from the manufacturer’s website. For example, the Energy Performance chart for Southwest Wind power’s 200W Air Breeze predicts 20-30 kWh (kilowatt hours) per month from 10-12 mph winds occurring 6 hours per day.

To put this in perspective, 30 kWh is less than 5% of the power consumed each month by the average household. Overall, the payback from a single, roof mounted turbine in tangible financial terms leaves a lot to be desired; especially in light of the fact that unlike solar, there is no Federal tax credit for residential wind power.

But anyone thinking about installing a rooftop turbine(s) is probably aware of this already. The rooftop wind enthusiast is not motivated by financial relief, but rather the intangible rewards of pride of ownership, walking the walk, or simple satisfaction as a hobbyist.

Motivation aside, it doesn’t make sense on any level to proceed with a wind powered project unless the three following requirements are met:

1. Higher than average cost per kWh. The more you pay per kWh for electricity, the more economical wind power becomes. A rule of thumb in the wind turbine industry states a residential wind powered system shouldn’t be considered unless you pay $0.10 or more per kWh for electricity.

The easiest way to determine your cost per kWh is divide the current monthly balance on your electric bill by kWh usage (also plainly stated on your bill).

2. Building codes. Visit your building department to find out if there are any zoning restrictions for roof top turbines. Don’t build your rooftop system first and ask questions later – only to be told it violates zoning laws and must come down.

3. Minimum wind speed. Wind speed of 7 mph, or 3 m/s (meters per second) is the start up speed for just about every wind turbine. However, in order to get any “juice” out of the turbine, minimum wind speeds of 10-12 mph for 6 hours per day are necessary.

Although wind speed charts for the United States and Canada are available to help site larger turbines, they’re of little use for rooftop systems because the data is collected at a minimum altitude of 30 meters (98.4 feet).

However, you can get a good idea of the wind speed at proposed turbine locations by purchasing an anemometer (wind speed meter) for around $150. The kit comes with a rooftop sensor, 60′ of cable and mounting hardware for the read out display. These are not data logging meters, so you’ll have to keep notes on your observations.

If you’re really serious about wind speed data collection, you can purchase a data logging anemometer kit with tracking software for $400.

Depending on where you live, wind speeds generally fluctuate with the seasons. Readings taken during the hot summer months of July and August, when you’re begging for a breeze, are not usually a reliable indicator of average yearly wind speed.

Also, rooftop turbines located at the edge of a long flat roof experience much more wind than those located on roof peaks.

If, after a month or two of collecting data you determine there just isn’t enough wind for a rooftop wind turbine, you can always resell the anemometer and turn your attention towards solar.

From San Francisco to New York City, rooftop wind turbines are hitting the home front. Rooftop wind turbines are being installed on both homes and businesses at an unprecedented rate due to several factors including the desire to save electricity, cut down owns dependency upon fossil fuels and as a visible symbol that one is doing their part to go green.

Critics of rooftop wind turbines say that they simply don’t work or don’t work as well as advertised. The critics are right in some instances and that is why the consumer needs to know what they are getting into and what to watch out for before investing in a rooftop wind turbine.

Some of the factors that will influence the output of the rooftop wind turbine include the design itself (horizontal or vertical axis), the kilowatt rating of the generator, where the rooftop wind turbine is placed, the angle or pitch of the roof, how much wind the region provides and any obstructions that may block the wind.

The design of the rooftop wind turbine is important for several reasons. Aesthetics is one of the larger reasons homeowners today would want to put a renewable energy generator atop their houses. Also, rooftop wind generators can be a status symbol that one is doing one’s part to help the environment, create jobs for others and lower bills in these tough economic times.

Some wind turbines make more noise than others. The biggest complaint about a series of rooftop wind turbines placed at the Logan International Airport in Boston has been from an office worker below that says they make too much noise.

As I’ve stated in other sections of this website, celebrities like Jay Leno and Ed Begley, Jr. have decided to place rooftop wind turbines on their homes and garages. In both cases vertical axis magnetic wind turbines were chosen to fill the bill.

Some homeowners state that vertical axis wind turbines in general are a little quieter than their horizontal axis counterparts. Rooftop wind turbines generally come with a kilowatt (kW) rating such as 5 kW, 10 kW or 20 kW that reflects how much electricity one can expect it to generate for one’s home or business. It is important to either have a large enough rooftop wind generator or several that add up to enough in order to provide the needed power.

Some rooftop wind turbines will work more favorably when on the edge of a rooftop, such as one that is long and flat (sort of like being on the edge of a cliff with an updraft). Others, however, on roofs with more angle or pitch will work more favorably in a higher location. Finding the right spot on the rooftop can add 5 to 40-percent more efficiency in electricity generation.

One of the most obvious points is for home and business owners in rather windless areas to not buy rooftop wind turbines but rather opt for other alternative energy resources. Wind maps may help some determine if there is enough regional wind to justify the purchase of building of a rooftop wind turbine. Buying an inexpensive anemometer and tracking results is also helpful before making a decision.

A less obvious issue when deciding on putting up a rooftop wind generator may be any obstructions current or future that could block the full wind from getting to the generator. Trees, other buildings, hillsides or even large vehicles can deflect the wind away from the turbine. If the rooftop is inside a city filled with buildings the wind path can become quite tricky as it may bounce from one structure to the next causing turbulence and an inconsistent flow.

Near homes, neighbors’ trees grow and leaf out, people may put up a second story or business may build structure in close proximity to homes which all may impact rooftop wind turbines. The important thing is to think about as may variables as possible when deciding if a rooftop wind turbine makes sense and the location that fits well.

That said, many people are now rolling back their electrical meters using rooftop wind turbines. Manufacturers of these turbines are busier than ever before. With a little forethought and planning, a rooftop wind turbine may make sense (and dollars) for homes and businesses across the nation. So, what are you waiting for? The time is now just like the name of this website indicates.