I'm awaiting my Model 3, and thought my charging situation was all set. (townhouse, 1 car garage, 200A service...I was just going to put in a 50A breaker to charge my Model 3 at 40A load....)
So now my charging situation will be: house with 100A service, no garage, gas appliances (which will reduce the load on the 100A box....)
I'm leaning towards the HPWC, since it will only be "live" once it's in the car and at it's set time....best to not have a live wire hanging off the side of the house.....but can I get away with a 50A breaker, and charge at 40A overnight when load is lowest? Or should I spring for 200A upgrade and put in an 80A breaker for the HPWC?
I am in the same boat as you. I am currently in a home with 100 amp service and i plan to run a 60 amp breaker to my Model 3 to use the maximum 48 amp charge rate. The only precaution i am taking is using Wire capable of 100 amps so i have the option to upgrade later. You mention you have Gas appliances so your in an even better situation than me.
The reasons I am confident 100 amp service is more than enough:
1) You can charge a 90 kWh battery (and most Model 3's will be smaller) with 240v @ 48A from 0-100% in around 8-9 hours. So even if you get home at 9 pm, your car is fully charged by 6 am. Plus unless you like living dangerously 99.99% of the time you will have more than 0% left on the battery.
2) I have used a home energy monitoring system for a couple of years now and even when the A/C, Oven, and Clothes Dryer are running (all are electric) we never get above 8 KW average load. Since i have 24 KW to play with (100A @ 240v) I have about 5KW to spare in case their is a peak i am not seeing.
3) The High voltage items above are running most often during the day or early evening and for the most part people charge their cars at night to take advantage of cheaper rates.
4) Within the car i have complete control of the charge rate. So If the house is full of guests and everything is lit up i can just turn down the charge rate for as long as i need to.
I say don't change a thing.