NEC 220.87 - Existing Loads from Utility Bill

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curious101

Senior Member
Location
Atlanta, GA, USA
Hi All,
Question regarding above listed: if I try to go by the utility bills to determine the maximum demand, but the monthly utility bills only list kWh as total usage for a certain number of billing days, do I convert this number for each month to get the peak demand kW data and then pick the highest value to multiply by 1.25 and add the new loads? If yes, is this kWh-to-kW conversion okay to use (basically divide the kWh by the total hours of the billing period)? https://www.inchcalculator.com/kwh-to-kw-calculator/
Please let me know if you have questions.
Thanks, and have a great day!
 
david luchini

david luchini

Moderator
Staff member
Location
Connecticut
Occupation
Engineer
curious101 said:
Hi All,
Question regarding above listed: if I try to go by the utility bills to determine the maximum demand, but the monthly utility bills only list kWh as total usage for a certain number of billing days, do I convert this number for each month to get the peak demand kW data and then pick the highest value to multiply by 1.25 and add the new loads? If yes, is this kWh-to-kW conversion okay to use (basically divide the kWh by the total hours of the billing period)? https://www.inchcalculator.com/kwh-to-kw-calculator/
Please let me know if you have questions.
Thanks, and have a great day!
Click to expand...
There is no way to get a maximum demand from kWH.
 
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d0nut

Senior Member
Location
Omaha, NE
curious101 said:
Hi All,
Question regarding above listed: if I try to go by the utility bills to determine the maximum demand, but the monthly utility bills only list kWh as total usage for a certain number of billing days, do I convert this number for each month to get the peak demand kW data and then pick the highest value to multiply by 1.25 and add the new loads? If yes, is this kWh-to-kW conversion okay to use (basically divide the kWh by the total hours of the billing period)? https://www.inchcalculator.com/kwh-to-kw-calculator/
Please let me know if you have questions.
Thanks, and have a great day!
Click to expand...
The error in your proposed calculation method is that it assumes the load is constant for the entire month. Since this assumption is erroneous, the calculation fails.
 
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