Circuit breaker panel capacity

Here is a general question, I am planning a project and will eventually get all proper permits but I want some advice to determine if this step is necessary
I am planning to install a steam room in a new bathroom and it requires a 35A, 220V dedicated breaker. My house has a 100A service panel with one 50A to the range, one 35A to the drier and about a dozen 20A wall plug circuits.
The question is: Is it likly that I will need to simultaniously upgrade the service panel to 150A when adding this circuit? What is the rule about the maximum capacity of a service panel?
I know it depends on where I live (CA) etc. I am just looking for direction before I go in for permits and get rejected for omitting something important.

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AutoTracer wrote:

The service load needs to be calculated per NEC 220-31. Add up the numbers and see what you get. 220-31. Optional Calculation for Additional Loads in Existing Dwelling Unit
For an existing dwelling unit presently being served by an existing 120/240-volt or 208Y/120-
volt, 3-wire service, it shall be permissible to compute load calculations as follows:
Load (kVa) Percent of Load
First 8 kVA of load at 100
Remainder of load at 40
Load calculations shall include lighting at 3 volt-amperes/ft2 (0.093 m2); 1500 volt-amperes for
each 2-wire, small-appliance branch circuit and each laundry branch circuit as specified in
Section 220-16; range or wall-mounted oven and counter-mounted cooking unit; and other
appliances that are permanently connected or fastened in place, at nameplate rating.
If air-conditioning equipment or electric space-heating equipment is to be installed, the following
formula shall be applied to determine if the existing service is of sufficient size.
Air-conditioning equipment* 100%
Central electric space heating* 100%
Less than four separately controlled space-heating units* 100%
First 8 kVA of all other loads 100%
Remainder of all other loads 40%
*Use larger connected load of air conditioning and space heating, but not both.
Other loads shall include the following:
1. 1500 volt-amperes for each 20-ampere appliance circuit
2. Lighting and portable appliances at 3 volt-amperes/ft2 (0.093 m2)
3. Household range or wall-mounted oven and counter-mounted cooking unit
4. All other appliances fastened in place, including four or more separately controlled spaceheating
units, at nameplate rating

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