101019-1950 EDT
I have done an analysis for a client where we are to replace all existing FO96 T12 fixtures with new 2 lamp tandem T8's.
This is past tense and thus implies you have done this, and probably you used some equation or equations, or graphs to do your analysis.
Part of our assessment is to show current kwh vs. proposed kwh and the reduction in consumption.
This is past tense or you have not yet installed the fixtures. This is not clear. I assume it was part of your analysis. Is all of the previous lighting on one meter with no other loads? If so do you have a year's worth of actual KWH used? Obviously you can not know what a future year's worth of actual energy will be consumed with the new lights until that year is over. What was the result of this assessment
Now our client is looking for the actual reduction in avg daily load. Is there a simple formula that can show the effect on daily load from this retrofit process?
Why do you expect a simple formula to provide an answer to the actual saving?
You can estimate a saving and that was what I would conclude "assessment" meant.
To get some real world determination of "actual" change in consumption you need to make some real world measurements and assumptions. One important part of a comparison is that the same light usage pattern must be used in both parts of the comparison.
For previous data you may be able to estimate energy usage based on power company meter data and somehow information on how much of this is a result of the lights. Future use you could do on a short time basis, and make a projection to a full year.
Probably a more useful method is to measure the power input to some of the old fixtures and some of the new ones. Get an average value for each old fixture, and an average for each new fixture. Then count old and new fixtures. Multiply the number of old fixtures by by the average consumption per old fixture. Then do the same for the new fixtures, and calculate the ratio. However, I assume this was done in your assessment.
So I am really confused on your question about an equation to give you some answer.
The real proof will be a comparison of next year's bill vs last year's. Where the split in years is when the fixtures were changed.
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