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What Size Turbine do I need?

Just a few easy steps to figure it out

Step 1.

Think about how much of your existing electrical consumption and $$ billing you would like to replace with “free” electricity from your Wind Turbine.   1/3, ½, all of it?  Since your Wind Turbine is a long term investment, think a little “long term” about the future cost of electricity. If you decide to replace ½ of your consumption and the price of electricity doubles ,,,,,,, your billing $$ will be what it is now, in addition to the cost of the turbine.  

Step 2.

Gather up the last 12 months electric bills. It doesn’t matter what the dates are as long as there’s a 1 one year group so that it covers all the seasonal variations. 

Step 3.

Fill out a chart with the numbers from your utility bills-  as shown on the example chart below.  (just take a blank sheet and write down the headings) 

Step 4.

Total up the columns: #Days, KW used, $$. Divide the KW used total by the # Days total. That will give you an average KW usage per day.  Then divide the KW per day figure by 24. THIS WILL BE THE AVERAGE KW per HOUR usage you need to make with your Wind Turbine to replace 100% your electricity. 

Once you know your average KW usage per hour. It’s easy to select a turbine because they are rated in maximum KW per HOUR. !!!!  There is one little catch in this. The wind doesn’t always blow at the correct speed to run the wind turbine at maximum rated capacity. Sometimes it doesn’t blow at all. So you need a “fudge factor”. A general easy rule is to use 33% or 1/3 of rated capacity for wind turbine production. 

The simple way to do this is just take your AVG HOUR KW times 3.

So, as in the example below - The AVG 1 HOUR KW useage is 5.3k , times 3 = 15.9KW.  Therefore a 15KW turbine roughly should do the job of replacing 100% of our current usage. If you only want to replace ½ of your purchased power, then a 7.5kw could suffice. 

A on "site"wind study over a year would give you a more exact “fudge factor”. But who’s to say whether that year was “more or less” windy than the previous. So, you must sometimes just make a best judgement.  If you have concerns then go one size larger on the turbine for your intial install or consider adding a solar panel supplement at a later date.

Here is a typical 30 year old, 2 story, 3 Bedroom, 2 Bath, that is ALL ELECTRIC (Furnace + AC). Its heated on on 3 levels with electric resistance heat. (3600 sq ft total) Below is a chart of the actual electric power comsumption for 2009.

            Billing Dates  2009                # DAYS                 KW USED                      $$

1              12/17-1/22/09                   36                           9188                       338.68

2                1/22-2/23                         32                            6912                       266.63

3                2/23-3/24                         29                            5001                       205.88

4                3/24-4/22                         29                            3967                       173.01

5                4/22-5/22                         30                            1661                         99.70

6                5/22-6/22                         31                           1249                       113.65

7                6/22-7/29                         37                            1691                       150.87

8                7/29-8/26                         28                            1479                       133.02

9                8/26-9/25                         30                            1590                       142.36

10             9/25-10/26                        31                           3124                       146.27

11           10/26-11/24                        29                           3729                       165.52

12           11/24-12/30                        36                           8119                       305.17

                                                         _____                        _____                     ______

Totals                                                378 days               47710 KW             $ 2240.79

47710 KW used, divided by 378 days = 126.21 KW per day.    Divide by 24 hours = 5.26 KW per Hour 

Another useful number from this chart is to divide the annual $$ by 12 to get a monthly amount. In this example the average monthly amount is     $ 2240.79/12 months =  $ 186.73 per month. 

This is useful $$ amount to know when you get to the point of calculating payback/loan terms. 

( It should be noted that this house has a 2 tier/time of year rate and as such the $$ amounts don’t seem to match the up/downs of kilowatt usage.  That’s why it’s important to get a year’s data and then average to the monthly amount.) 

For more information, visit www.iowawindturbines.com

Source: http://iowawindturbines.com

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