A Free-Market Energy Blog

Beware Windpower’s “Homes Served” Claims

By Glenn Schleede -- February 4, 2009

People who use the phrase “homes served” to describe the potential output from one or more wind turbines either do not understand the facts about wind turbines, believe false claims put forth by the wind industry, or are trying to mislead their reader or listener.

False statements about “homes served” by wind developers and their lobbyists are bad enough, but it is discouraging to hear politicians, reporters, and others adopt and regurgitate them.

The concept of “homes served”
The concept of “homes served” has long been used in the electric industry as a way of giving some idea of the amount of electricity that would be produced by a proposed generating plant without using such terms as megawatt- or kilowatt-hours, which mean little to most people. The concept is always misleading since residential users of electricity (i.e., “homes served”) account for only 37% of all U.S. electricity use. [i]

Claims about “homes served” by a proposed “wind farm” or other generating unit are usually based on a three-step calculation:

Start with an assumption (i.e., a guess) about the amount of electricity that would be produced annually by a “wind farm” or other generating unit, in kilowatt-hours (kWh) or megawatt-hours (MWh).[ii]

Employ an estimate (in kWh) of the amount of electricity used annually by an average residential customer in the area or state where their “wind farm” is located. [iii]

Divide the assumed annual production of electricity by the estimated annual average residential electricity use.

“Homes Served” can be useful when talking about reliable generating units
Although misleading, the concept of “homes served” has some validity when used to describe the output from a reliable, “dispatchable” electric generating unit, that is, one that can be called upon to produce electricity whenever it is needed. Such generating units are the ones that are counted on by the electric industry to provide a reliable supply of electricity for customers every day, at all hours of the day, year round.

“Homes served” is NOT a valid concept when referring to wind turbines and “wind farms”
Using “homes served” when talking about wind turbines and “wind farms” is both false and misleading for several reasons.

1. NO homes are really served by wind.
No homes are served by wind energy because wind turbines produce electricity only when wind speeds are in the right speed range (see below). Homes using electricity from wind must always have some reliable energy source immediately available to provide electricity when there is insufficient wind unless the residents are content to have electricity only when the wind is blowing in the right speed range – a condition that few in America are willing to tolerate.

2. Electricity from wind turbines is inherently intermittent, volatile, and unreliable.
Wind turbines produce electricity only when the wind is blowing within the right speed range. Wind turbines typically start producing electricity at about 6 mph, reach rated capacity at about 32 mph, and cut out at about 56 mph. Unless a home owner has an expensive battery storage system, such volatile and unreliable output wouldn’t be suitable for lights, heating, computers, appliances, or many other purposes .

3. Electricity from “wind farms” is seldom available when most needed by home users.
Again, the output of wind turbines is dependent on wind conditions. Depending on the specific area, winds tend to be strongest at night in cold months. However, electricity demand in most areas of the United States is heavily concentrated during daytime and early evening hours. Even worse, wind turbines cannot be counted on to produce at the time of peak electricity demand, which often occurs in late afternoon on hot weekdays in July and August. At the time of peak electricity demand, wind turbine output may be in the range of 0% to 5% of rated capacity.
4. The electricity produced by wind turbines is low in value compared to electricity from reliable generating units.
That’s because it is inherently intermittent, volatile, unreliable, and not available when most needed—as described in points 2 and 3 above.

 5. Not all the electricity produced by a wind turbine actually reaches customers or serves a useful purpose. Some electricity is lost as it is moved over transmission and distribution lines that carry the electricity from generating units to homes, offices, stores, factories and other users. The amount of electricity that is lost depends on the distance and the condition of lines and transformers. These “line losses” are a significant issue for wind energy because huge, obtrusive wind turbines (often 40+ stories tall) and “wind farms” are not welcome near metropolitan areas that account for most electricity demand. Therefore, they are often located at some distance from the areas where their electricity is needed and so require expensive transmission-line capacity, which they use inefficiently. (Ironically, the lucrative federal tax credits provided to “wind farm” owners are based on electricity produced, not the lesser amount that actually reaches customers and serves a useful purpose.)

6. Claims of “homes served” by wind energy are additionally misleading because of the high true cost of electricity from wind turbines.
Claims that the cost of electricity from wind turbines is “competitive” with the cost of electricity from traditional sources are false. Such claims typically do not include the cost of (a) the huge federal and state tax breaks available to “wind farm” owners,[iv] or (b) the cost of providing the generating capacity and generation that must always be immediately available to “back up” intermittent, unreliable wind turbine output and keep electric grids reliable and in balance.

Claims of “homes served” should always be challenged
 Any use of the “homes served” assertion in connection with a “wind farm” should be challenged, whether the assertion is from a wind industry lobbyist, other wind energy advocate, political leader, other government official, or reporter. They should be required to explain each of their assumptions and calculations, and admit that industrial scale wind turbines are useless unless reliable generating units are immediately available to supply electricity when wind is not strong enough to produce significant electricity. Almost certainly, their assertions will be false.

What valid claim could wind industry officials make?
As explained above, wind industry developers, promoters, and lobbyists – and politicians and reporters — should never use the false and misleading “homes served” metric. In theory, they could justify an assertion that the estimated amount of electricity produced by a “wind farm” – once discounted for line losses which are likely to be in the range of 5% to 10% — may be roughly equal to the amount of electricity used annually by X homes – after doing a calculation such as that outlined earlier. However, as indicated above, even this assertion would be misleading because it ignores the fact that the output from wind turbines is intermittent, volatile, unreliable, and unlikely to be available when electricity is most needed.

Other false and misleading claims about wind energy
As shown above, “homes served” is not the only or the most important false claim made about wind energy. Other false claims about wind energy include the following:

It is low or competitive in cost. In fact, its cost is high when all true costs are counted.

It is environmentally benign. In fact, it has significant adverse environmental, ecological, scenic, and property value impacts.

It avoids significant emissions that would otherwise be produced. In fact, it avoids few.

It provides big job and economic benefits. In fact, there are few such benefits.

It reduces U.S. dependence on imported oil. In fact, it does not.

It reduces the need for building reliable generating units in areas experiencing growth in peak electricity demand or needing to replace old generating units. The opposite is true.

Such claims as these have been made often during the past decade and more by the wind industry and other wind advocates. Only during the past 3–4 years have these claims begun to be demonstrated as false and misleading. The facts about wind energy are beginning to show up in the media but, unfortunately, have yet to be understood by most political leaders and regulators.

[i] According to EIA data, the percentage of total electricity use accounted for by residential customers in 2007 varied from lows of 16.3% in DC and 16.7% in WY to 44.6% in AZ and 51.0% in FL – with a nation-wide average of 37%. http://www.eia.doe.gov/cneaf/electricity/esr/esr_sum.html

[ii] Assumptions about output from proposed “wind farms” start with the rated capacity of the wind turbine(s) in kWh, multiplied by the number of hours in a year (usually 8760) and multiplied by the assumed “capacity factor” of the wind turbine(s). In fact, actual capacity factors can be known only on an after-the-fact basis. “Capacity factor” is calculated by dividing actual annual production in kWh by 8760 (hrs per year) times the rated capacity of the turbine(s) in kW.

[iii] Annual residential use of electricity varies widely. According to the U.S. EIA, average annual residential electricity use nationwide during 2007 averaged 11,232 kWh — varying from lows of 6,360 kWh in Maine and 6,960 in California to highs of 15,660 kWh in Alabama and 16,128 kWh in Tennessee. http://www.eia.doe.gov/cneaf/electricity/esr/esr_sum.html

[iv] Wind industry officials have indicated that just two federal tax breaks account for about 2/3rds of the economic value of a “wind farm.”


  1. Tom Stacy  

    Thanks to the owner of this blog for publishing this interesting and factual paper. Who would have known simple claims about energy production could be so insidiously greed driven? Maybe this art form is left over from the days of “the smartest guys in the room,” Enron and their wind energy division now owned by General Electric, who, coincidentally, also owns NBC.

    Along with those expensive batteries Mr. Schleede mentions, it is noteworthy that less than of half of the alternating current pressed into chemical energy in batteries can be recovered later in the same AC 110 60 cycles form. What this means essentially is a doubling doubling the ongoing price of their squirreled away portion of wind energy generation which did not occur at the moment it was needed.


  2. Allen  

    “The amount of electricity that is lost depends on the distance and the condition of lines and transformers. These “line losses” are a significant issue for wind energy because huge, obtrusive wind turbines (often 40+ stories tall) and “wind farms” are not welcome near metropolitan areas that account for most electricity demand.”

    I wouldn’t even get to that. Most of the potential for wind is on the Great Plains and even places like Dallas or Denver, which really are far away from where most Americans live, aren’t really all that close to the areas on the plains where the best winds occur. Of course “best” would still result in far from being good enough.

    I guess that’s why it drives me nutts when proponents say “well, we just need to build enough so when wind isn’t blowing in one area, it is in another and we can get it from there”.


  3. Major Mike  

    The Silent Windmills of Altamont

    We had Christmas with Alice’s daughters’ families in Walnut Creek, about forty miles east of San Francisco, overnighted with a friend in Livermore not far from the five-acre ranch where we lived for nine years, and on the last day of 2008 we set off for Southern California via Highway 580. Soon we were passing through the Altamont Pass, famed as the site of a massive free rock concert in 1969 featuring the Rolling Stones with the Hell’s Angels as security, or maybe not.

    Now Altamont Pass is a much quieter place, the site of what was once the largest wind farm in the world. As we drove past it on a winter afternoon, not one of the 4,900 windmills was turning. When we came back through Altamont eight days later, no windmill was turning. On the basis of the consistent, persistent cold weather during our eight-day sojourn, the Altamont wind farm probably didn’t produce much, if any, electrical power during that period.

    I wasn’t surprised. During our nine years in Livermore, Alice and I could see many of the windmills from our back yard. As often as not, none would be turning, particularly in the morning, in the evening, in the winter, and from my very limited personal observations, at night (it was too dark to view the still windmills except for the few times I drove through Altamont Pass after dark). The reason for the rampant inactivity is quite simple: windmills are powered by the sun creating temperature differentials, and the resultant movement of air masses.

    During the day, the San Joaquin Valley warms rapidly, and the Pacific Ocean doesn’t. Warm air rises from the land, and cooler air rushes inland through the Altamont Pass, powering the windmills as it passes. The land cools faster than the ocean after the sun goes down, and the process is reversed – except the cooling is slower, and the air movement is also slower, providing far less energy to move the windmills.

    Wind farms like the Altamont Pass are very inefficient, and wouldn’t exist without heavy subsidies and wishful thinking on the part of politicians and environmentalists. The Altamont wind farm only operates at an average efficiency of 22 percent (producing about 125 megawatts from a 576 megawatts capacity). In fact, because so much power is generated by higher windspeed, much of the energy comes in short bursts; half of the energy available comes from just 15% of the operating time.

    To an honest engineer, the math is very simple: moving air has a very low energy density and is unreliable – a huge land area is needed to harvest energy from it. The United States is blessed with stronger winds than Europe, and still wind generates only about one percent of our electricity. According to the Department of Energy, wind farms “could generate 20% of US electricity by 2030.” Apparently no honest engineers were consulted before the Department of Energy made this asinine pronouncement. Wind farms will be lucky to stay at one percent, given our current economic downturn.

    An honest assessment of wind power is that it can only be relied on to “supply a low proportion of total demand.”
    When a wind farm is erected, the fossil fuel generator providing power to the area can’t be closed and torn down. Based on my observations, and the observations of others, it still has to run almost eighty percent of the time, and that would be true even if the capacity of the wind farm quadrupled, quintupled, or even exceeded ten times the capacity of the old generator. Why? Simple. No matter how big a wind farm you build, when the wind isn’t blowing, it isn’t generating.

    But the need for electricity doesn’t wait for the wind to return.

    Where will funding for wind farms arise? From the Federal government, running record deficits while over a trillion dollars is going to bail out banks and automobile manufacturers? From the states? California is in a forty billion dollar hole, with deep cutbacks in education and health services, to name just the neediest state programs. From investors? They’ve been eaten alive by the recession, and wind farm investments make sense only if heavily subsidized by the government – and then they still don’t make sense.

    The next time you admire a wind farm, chances are that you will be observing wind mills in inaction. If that is the case, think of all the politicians and engineers that have sold their integrity to create an expensive and wasteful eyesore.

    One that you helped build, and must subsidize to operate.


  4. Ed Reid  

    “[ii] Assumptions about output from proposed “wind farms” start with the rated capacity of the wind turbine(s) in kWh, multiplied by the number of hours in a year (usually 8760) and multiplied by the assumed “capacity factor” of the wind turbine(s).”

    The “kWh” above should be “kW”.

    Otherwise, right on point.


  5. Ed Reid  

    Hi, Glenn. I hadn’t noticed you were guest blogging here.



  6. Bob Sykes  

    A farmer in my county installed a medium sized windmill on top of a cleared hill last spring. It goes days, maybe weeks, at a time NOT turning. In the fall, which is windy here, the mill did turn most days. But over the last 9 months it has generated electricity only about 5% of the time. I would really like to know how much money the farmer has lost.


  7. Fred Stovel  

    To see a graphic depiction of action production versus capacity, see the data produced by the BPA at http://www.transmission.bpa.gov/business/operations/Wind/baltwg.aspx
    This graph is updated every five minutes and the output is in a spreadsheet for someone to graph on an annual basis. It would be nice if every wind farm was displayed like this.


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  9. Sherri Lange  

    Homes served has always piqued many of us. Just another fanciful bogus claim. With world stats on performance hovering at point two of one percent, net zero, it is hard to imagine even a single toaster in a community being powered. Very superb analysis. Thankyou.


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