Upgrade subpanel

Question

I am looking to add a 240v 50amp outlet to my garage for charging the EV. With the help of folks on this forum I found that I need to expand my subpanel to add more breakers before adding a line to the garage.

I have a main panel (200amps) and a sub-panel (100 amps). They are both full. Can I replace four 15amps breakers with 2 multipole breakers to open two slots in the subpanel?

Here is what the main panel looks like:

Here is the subpanel:

On this subpanel can the slot #3 and #4; and #6 and #7 be merged with multipole breaker? If yes, I can bring two circuits from main panel to this, and use the main panel's two open slots to add a 240v 50amp circuit. Will this work and be safe?

If not, is upgrading the subpanel the only other option?

Thanks for all your help!

Here is the picture of the subpanel breaker from bottom. Shows the brand.

Here is the outside main panel.

Panel and sub panel using the 10 gauge wire:

Answer 1

Looks like you're on the hook for a new main panel

Your problem is threefold. First, your main panel is full to the brim with double-stuff breakers, which means that there's no room for an EV breaker there. Second, since the subpanel feeder comes off the main panel, which is full of double-stuff breakers, the largest feeder you can run from your current panel is 50A as larger double-stuff breakers aren't a thing. Finally, you'd be limited to a paltry 30A if you tried to run the charger from the subpanel as QO double-stuff breakers top out at 30A instead of 50A to begin with, despite the subpanel feeder being (presumably) capable of 50A.

So, you'll need to replace that whole main panel with a new, larger panel. Fortunately, the fact your main disconnect is outside, separate from the panel, makes this a fairly reasonable DIY job. The new panel of choice for this will be a TLM4020C80G; this provides you with an additional 20 full-size spaces over your current panel, which is enough to accommodate future GFCI/AFCI upgrades, your car charger, and a larger feeder to an upgraded subpanel, while allowing you to "transplant" your existing circuit breakers for the time being.

Note that in order to make sure the car charger won't overload your main panel, you'll have to do a NEC Article 220 load calculation to make sure you have the 40-50A of wiggle room required for a Level 2 EVSE. For this, we'll need the square footage of the whole house, as well as the nameplate ratings of the air conditioners, range, disposal, and Jacuzzi.

Answer 2

Your sub panel is listed for doubles 6/12 the problem I see is the main panel the largest breaker is 50 amps so there will need to be a change for the breaker and feeder, now comes the normal news for heavily loaded panels.

You will have to do a complete load study or have it done by a pro, it looks like your home was a custom job by the number of the circuits and a standard load calculation that may be suggested would not be acceptable due to the number of circuits.

A load study is basically finding the peak loading and some jurisdictions will allow power company peaks as the value, if your peak value is around ~130 amps you could add the EV charger.

From what I see the sub is only fed by a 50 amp circuit so this will need to be upsized (breaker and feeder wires)

So in any case the minimum needed will be a larger breaker for the sub and a larger feeder when going this far I would suggest a larger sub panel I love square D but there tandems and quads are more expensive and dropping a full side panel is usually less expensive.

If you are over ~130 peak then a service upgrade is required. Where do I get the 130 amp peak? You can only use 80% of the unused amount of a service so you need about 62.5 because of the 50 amp but most jurisdictions round up to 70 in this case I have done many of these over the years by turning everything on heat or AC the larger and taking measurements .

Looking at your panel I would bet you have the available especially if you have upgraded to LED lighting.