I want to add some circuits to my 100 amp panel on my home.
How do I calculate whether I have any room for additional load?
I have a subpanel in the studio which is set from a 60 amp breaker on the main panel...
Standard size home 2000 sq ft--part of the home has a studio apt.
3 fridges
2 micros
2 stove tops
1 oven
1 gas furnace
1 dishwasher
1 washer
1 dryer
2 disposals

No air, no heat pump, no spa, or other

Sorry , if I tell you how to do the calculations, then why would anyone need me?

The calcs are to difficult to tell you and make you understand. Takes electricians 4-5 years to learn most of this stuff, and then most don't even then understand. Been doing this 30 years and I just figured it out last year.

Anyone else want to explain, go for it.

Seriously, need to know:

What are the new circuits for?

Are you adding livable space to the total square footage of livable space ?

Does the 2000 SF include only livable space, and the apt? No basement. Garage, etc.

Is the oven a recess unit? Double or single oven? 4 burner cooktops only?

Electric or gas dryer?

Please answer and we can go from there.

How are you doing with this? Have you been able to collect the info I need to help do the calculations?

What are the new circuits for?

Add a microwave/radiating oven, that would be hard-wired. A plug circuit (4plugs?)in the garage, and 3 new lite circuits in the kitchen

Are you adding livable space to the total square footage of livable space ?
No.
Does the 2000 SF include only livable space, and the apt? No basement. Garage, etc. Yes, just the livable, which includes the studio apt. No basement.

Is the oven a recess unit? Double or single oven? 4 burner cooktops only?
Oven is a drop-in type that rests on the counter. Single oven with 4 burners stovetop.
Electric or gas dryer? Dryer is electric.

The newer 100 amp subpanel was installed when the addition was done (the apt) and it feeds off the main panel with a 60 amp breaker. The 100 amp main panel does not have a main shutoff and is older Federal type.

Thanks for your help!

The existing load is borderline for 100 amp service. I believe the added circuits will be fine, but practicallity depends on the activity in the home, how may residents will be using the load.

The existing 100 amp service is sufficient to handle the load, however, you may consider upgrading to a 200 amp some time in the future. And certainly you will want to change the FPE panel,since there has been problems with FPE in th past, and is no longer manufactured, and barely supported with spare parts.

A new service will add to the value of the home, and someday, the FPE panel may draw attention and be requied to be replaced by an insurance company.

Thanks. I agree that the FPE will need replaced. The breakers are loose and I don't like that. I think upgrading to a 200 amp will be major because I think a new line will have to be run from the other end of the house at the meter to handle the new service. It may be worth it though.

Maybe I will just change the panel to a better newer 100 amp panel now and add the circuits. You think the added circuits will not overload the system if the main panel is left at 100 amp?

Thanks for the input.

Since the main 100 amp panle does not have a Main Breaker, the MCB must be outside at the meter location, if you change the FPE panel, install a 200 Amp rated panel, and then when you do upgrade the service entrance, meter and feeder, the panel will be already installed.

No the added circuits do not add much more load, and do not affect the load calculations.