Power Factor Calculator test new | Abraxas Energy Consulting

XBAR: 26

No of rows: 130

Standard Deviation 472.94615384615

Calculate Cv and Determine if there Should be More Measurements

18.190236686391Take more samples

Calculate Maximum Error

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When you do Option A or B M&V, sometimes you need to take measurements of a sample of a large number of devices. It can be a waste of resources to measure ALL of the devices. So often we measure just a portion of them, and assume their average represents the entire population.

Use this calculator to estimate how many measurements you need to take.

A great source of information on sampling for M&V was produced by BPA. It can be found here.
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If you are not sure what CVs to use when you estimate sample size, here are some suggestions.

For pre-retrofit lighting fixtures, use 0.3
For post-retrofit lighting fixtures, use 0.2
For occupancy schedules, use 0.5
For motor kW, use 0.5
For package units use 0.5

Remember, the sample size calculator gives you an initial estimate of how many measurements you need to take. But as you take measurements, you may find that you don’t need as many measurements, or … that you may need to take more measurements than this calculator estimated. That is why we calculate the precision to ensure that the measurements meet your precision requirement.

If you don’t know what I am talking about, read the BPA manual, or get your hands on our webinar we put together on sampling. (You are going to have to ask us for a link, as we have not posted it yet.)

Sample Size Calculator

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XBAR: 26

No of rows: 130

Standard Deviation 472.94615384615

Calculate Cv and Determine if there Should be More Measurements

Calculate Maximum Error