In today’s Bangor Daily News, an article titled
Small-scale windmills generate mixed reviews” documents the unimpressive results that some Mainers have received from residential windmill installations.

In the article, as well as in the particularly lively comments section, there is a lot of discussion about site and design being key to a successful wind installation. We agree, and add this: very few areas have the potential to be a successful and economically viable site for wind.

Wind Vs. Solar:

Solar vs Wind Resources
A National Renewable Energy Lab map of solar resources (top) and wind resources (bottom) of the United States.

While most of the state of Maine is rated as a “poor” wind resource, all of Maine receives 4 or more kWhr/day of harvestable sunshine.

Maine’s Limited Wind Resources

A glance at Maine’s 50-Meter Wind Resource Map shows that most of the state of Maine is a poor or marginal wind resource.

A US-DOE wind map confirms this, by showing most of the state of Maine being in “Zone 2” for wind, meaning roughly 10mph wind speeds under ideal conditions at 33 feet – barely the minimum speed require to turn most wind turbines.

Even if your home sits in a windy spot, you need to account for trees, neighboring homes, hills, etc., not to mention the building code challenges and aesthetics of erecting a windmill.

Compare this to solar, which is basically ubiquitous. Provided you have a clear space that receives sunlight from 9AM – 3PM, you can enjoy the benefits of a solar electric or solar hot water system.

And unlike wind, if your site is initially too shady, you can add to your solar resource just by doing some tree work!

Wind Vs. Solar: The Fine Print

An average small-scale windmill costs about $15,000, prior to any rebates and incentives. This windmill, if we go by the optimistic specifications provided by the manufacturer, will produce 4,800 kWh a year.

For roughly the same cost, we could install a 3KW grid-tied solar installation. Using real-world data (the PVWATTS tool for Maine’s solar insolation), we estimate that the solar array will produce 3,840 kWh a year of electricity.

So, why not choose wind and get an extra 1000 kWh/year?

The reality is: very rarely will wind live up to its expectations.

From the Bangor Daily News article cited above:

While wind may be the fastest-growing electric energy source, home windmills aren’t for everyone, according to Richard Hill, professor emeritus of mechanical engineering at the University of Maine.

“If you have a great deal of money, and you hate the public utility and if you think you live in a windy place, you’ll be very disappointed when you put up a windmill,” Hill said recently. “You may, however, be justified because you’re interested in principle.”

… his windmill hasn’t delivered more than 100 kilowatt-hours a month, although it was advertised as capable of generating 400 kilowatts-hours a month. “I can tell you it doesn’t generate anywhere near that,” he said. Arnold has found that the wind must blow at least 8 mph to get his windmill going.

We also got this testimonial from some Shelter Institute graduates who installed their own wind system as well as solar power:

I think the main lesson we have learned (and would like to pass along to others) is that PV panels (solar panels) are much more cost effective as a means of autonomous energy production than wind, unless the wind site is very unique …

We did our own informal wind survey and felt fairly confident we’d get at least 1 kWh of production daily in the winter months (but only when the prevailing winds shifted to northerlies), and we’ve met that.

However, many people we’ve spoken to have mistakenly used turbine specs rather than an integrated formula for wind speed and time to calculate what they will generate, only to be disappointed in the small amount of energy they actually are able to produce.

The bottom line? Dollar-per-dollar, a solar system will outperform a wind system in nearly all real-world applications.

Reliable Sun Energy

GO Logic Passive Solar Home - Belfast, Maine
This solar electric system will displace roughly 250,000 lbs of C02 over its expected 50-year lifespan!

A Word on Reliability

It’s also worth noting that the value of a long-term renewable energy is directly related to the reliability of that investment. Solar panels have no moving parts, are warranteed for 25 years, and are expected to last double that.

An average warranty for a wind power system, in contrast, is only five years.

The expected life of a wind mill, under the best of circumstances, is around 25 years, half that of a solar installation.

Over the life of the system, the solar array will generate roughly 200,000 kWh, nearly double that of the wind – should the wind system perform to optimistic specifications over an optimistic lifespan.

Reliability, Economics, and Aesthetics

While ultimately we want to encourage everyone to find their personal path off of oil, we also have a duty to ensure that we recommend reliable, economically smart choices for our customers – which is why ReVision chooses to recommend and install grid-tied solar electric and solar hot water systems, and not wind.

With superior life expectancy, more reliable performance, better aesthetics, and better rebates, solar is the clear choice for clean, renewable electricity.