Can I calculate connected load from utility bill?
Can I calculate connected load from utility bill?
(OP)
Hello,
I am in the initial stages of applying for a service upgrade for one of our facilities. I have the utility bills for the past 2 years, and I have the average PF and Demand values for each billing period.
Example:
The last biling period has:
PF 86.46
Demand 204.52 KW
We are looking at adding more equipment to this facility. It currently has a 200A service, and we are looking to upgrade to a 400A. I am being asked to provide the Connected load and the expected demand. Can I estimate this from the utility bill, and add the load values from the specs of the new machines we are adding?
This is my first project of this type, forgive the simplicity of the question.
Thanks
I am in the initial stages of applying for a service upgrade for one of our facilities. I have the utility bills for the past 2 years, and I have the average PF and Demand values for each billing period.
Example:
The last biling period has:
PF 86.46
Demand 204.52 KW
We are looking at adding more equipment to this facility. It currently has a 200A service, and we are looking to upgrade to a 400A. I am being asked to provide the Connected load and the expected demand. Can I estimate this from the utility bill, and add the load values from the specs of the new machines we are adding?
This is my first project of this type, forgive the simplicity of the question.
Thanks






RE: Can I calculate connected load from utility bill?
You could also do a brief load study during peak conditions (winter or summer depending on HVAC loads).
RE: Can I calculate connected load from utility bill?
I have the peak demand over the last 2 years, 273.04 KW
Now if I know that my new machine is 3 phase, 600 V, 72A (peak), then I would I know that the demand of my machine would be:
P = 1.73 * 600V * 72A
= 74.7 KW
And my new peak demand would be: 74.7 + 273 = 347KW?
At this demand, would a 600V 400A service be adequate?
Average PF over the last 2 years was 90.54.
Thanks
RE: Can I calculate connected load from utility bill?
Assuming a power factor of 0.9, your peak demand from the last two years would have been about 303kVA. This equals 292 amps on your 200A service! I'm surprised your main overcurrent device did not trip. Are you sure your numbers are accurate? If so, your service should be upgraded whether you add loads or not.
Adding your new load of 72A will result in an expected peak demand of 364A (assuming 90% power factor for the new load).
A 400A service can accomodate a 320A load continuously, or up to a 400A load temporarily. I would assume that since you had no problem with 292A on your 200A service, that most of the load is not continuous. I would expect a 400A service to be fine, but you will not have much spare capacity for future loads.
RE: Can I calculate connected load from utility bill?
273.04kW/0.85pf(assumed) = 321kVA peak recorded
+
Sqrt(3)*0.6*72 = 75kVA
321+75= 396kVA - Assuming machine is always working this is your "worst case/peak" scenario demand load, not your connected. For your connected load you have to add all the individual loads in your building. The demand is lower because not all of your connected loads are energized/working all at the same time.
Anyways I would add 25% to the total demand for future expansion. This all gives you 495kVA.
At 600V service this gives you 495/(sqrt(3)*0.6) = 476A which comes out to a 600A, 80% rated CB. I would personally go with the 600A service based on the numbers you provided.
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RE: Can I calculate connected load from utility bill?