Strong disagree. Impulse/inrush current is critical

Install a 20amp circuit and be happy.

The code is for everyone not just you and is conservative for a reason.

you can approach adding panel ampacity one of two ways

you can use the NEC formula as you’ve discussed

or you can use usage data

Electrical code doesn’t care what your usage is.  It cares what your max usage can be with what’s installed.   You need a 200amp panel to be code compliant. NEC says you’re maxed out.

If you DIY and don’t pull a permit you’d probably be fine.   No licensed bonded electrician will touch that job on a 100amp panel.

The standard method is good when you are building a new house and haven’t picked appliances. It builds in a lot of room for future expansion. The optional method uses actual loads but still has a pretty big buffer because they don’t know how someone is going to run them.

It looks like the 2026 code drops from 3VA per square foot to 2VA per square foot. That makes sense because lighting is more efficient than ever. It’s probably still too high, but they want to leave room so you can plug in whatever you want (within reason) to receptacles around the house.

The average over an hour doesn’t tell you much though? For example when compressors kick in (fridge, freezer, heat pump) the amperage spikes considerably for a brief moment which is not going to be reflected in the average.

Same with running a microwave to reheat something, a hair dryer, …

An electric stove and emergency heat from an air handler would be almost 100 amps alone

I am an electrician and I have a sub panel that handles everything in the house. Would ya figure I had that whole sub panel “temp” fed on a 20a 120v circuit for over a year. I do have all gas heating appliances, but My amp probe never saw more than 12a pulled. Usually like you are seeing with only 2-3amps being drawn.

Now car chargers are unlike other loads. They are constant. I dryer or oven cycles on and off, but those chargers are going to be a steady flow. This builds more heat. 32amps seems to be common. Fed on a 40a rated line. Going #6 with a 50a plug and having a plug in charger could be cheaper than a hardwired unit bought through a contractor.

The amp ratings are what they are to prevent fires. It’s not about average usage, it’s about instantaneous usage. If you were to go ahead with your plan and at some point in the future, you had everything running at the same time, you risk a fire.

It’s not about your average case, it’s about edge cases. The electric code is not about capacity management, it’s about safety.

Guessing you don’t have electric heat or a large AC?

You can also install a controller for the charger so if you somehow end up using too much at once it will not allow the charger to turn on or it will turn it off until your usage reduces. Much cheaper than 200 amp upgrade

I’ve been considering a similar upgrade. Also a heat pump, water heater, and maybe induction range/stove. My current consumption over the last 2 years is also very low. But my worry is having it trigger frequently.

Seems like a smart panel (not cheap) could help by deprioritizing the charger or the heat during a rate spike. I haven’t moved forward but need to make a plan.

I presume you mean EV charger? Get one with dynamic load management, then it zero-rates and you’re good to go on any panel. Even panels close to capacity aren’t using anywhere close to 80% except for a few peak usage times when multiple things kick on at once.

This is exactly what the emporia pro charger is for. And it comes with a vue.

It’ll adjust charging based on your current usage.

NEC allows active load management very well. If your charger monitors you panel load then it basically doesn’t even get counted in your load calculation. Many EV chargers come with active load management (Tesla wall charger, Emporia, etc.) and it’s becoming a common feature.

It is bullshit considering the utility portion of the upgrade happens entirely in the office.

Technology connections did a video about having only 100amp service and using a smart panel to ensure nothing goes above 100amp

https://youtu.be/CVLLNjSLJTQ?t=944

Just get a Wallbox with the load monitor. Saves you from freak overcurrent but allows a good level 2 charger. With load monitoring that shuts the charger if there’s overcurrent you can zero out the charger contribution in the NEC calculation.

Get a soft start for that heat pump and it’ll ring those start up amps wayyyyyy down.

Just get a load shed device. It monitors your amp draw and will disconnect the charger if need be.

Idk about code, but practically you could exceed that limit. But to do so you would need some sort of smart system to manage the rare case when you actually pull over the limit.

You need five minute interval data if you want to use AMI data in lieu of a load calc.

Peak average is a bit meh. You can pull 0A for 45 minutes, but then 80A for 15 minutes and your average is 20A.

So not really safe to go that route. Vue will be much better if you can see every 1 or 5 minute intervals. At least you’ll see real time. Though it’s the rare times. 2 air heat-pumps pulling 12A each, it’s Thanksgiving and your using the entire stove. Using the microwave and other high amp kitchen devices. Have family over so every light is on. Running all the TVs. Water heater running all day with constant water use, someone decides to toss a load in the dryer and the girls are using the hair dryer.

No one wants to deal with a tripping main.

If you’re on 100A without issue and want to add an EV, only the individual knows their potential use. But something like an EV is easy to load shift or just charge at 16A.

I know for me, 100A isnt happening but I can’t speak for anyone else.

Ignoring what you feel is BS and getting back to reality…

Emporia produces a smart level 2 charger called Emporia Pro Level 2 EV Charger that lets you avoid the $7k upgrade.

When the home uses heavy loads simultaneously (such as a heat pump, electric dryer, or range), the charger automatically ramps down its charging rate in real time to prevent the panel from tripping the 100A main breaker. Once household load drops, charging speed dials back up automatically.

Making the standard calculations a non issue.

The electrical codes were written so that people don’t burn their houses down and so that you can get insurance. But you do you man.