I have got a couple different opinions from electricians and they all tell me something different. One said I could make room by pigtailing and another wanted to install a sub-panel to make room. Their prices were also between $1.5k and $2k. I need to add a 50amp breaker to this panel. What would be the easiest, most cost effective yet safe way to do so? The 20amp breaker on the left highlighted in yellow is not in use, so that can be removed. The two 15amp breakers on the bottom right feed the LED lights in my house, and carry a relatively small load.
I would go with a larger panel, it looks like you could add another quad breaker since the existing panel is a 8-16 but you are out of space again, to save some $ I would add a sub and move some loads over to the sub and feed from this panel that would save some $ and require less rewiring and the need to bring everything up to current code that is usually required for a complete panel replacement. Personaly with the very small panel you have I would bite the bullet and replace it with a larger 40 or larger slot panel. It looks like the existing loads plus a new 50 you would probably be ok with a 200 but we would need to know the needs like what type heating, water heater and range / AC? Is used in the home.
A triplex breaker will let you fit the 50A breaker into this unit...
You can fit a 50A/240V circuit into this panel, and get rid of the alien breaker (the BR120 in the far bottom left is not approved for use in this Siemens meter main), by replacing the two bottom-left breakers (the half-used Q2020 and the errant BR120) with a Q22050CT, then landing the two existing 20A circuits on the outer poles and the new 50A circuit on the inner poles.
But, you'll need to have your electrician check some things first
However, this does not mean your service can handle the additional load. You will need to have an Article 220 calculation run on your house at this point in order to ensure that you won't overload the 200A service -- if you charge ahead without this, things will mostly work, but you risk tripping the main breaker due to having too many things on at once.
Options for future expansion here
While the addition of your new circuit does fill up this particular panel, you are not without expansion options, either. Moving some circuits to the indoor subpanel is an option provided it has the spare spaces and ampacity to support such; even if it is short spaces, the fact it's a subpanel makes replacement relatively easy.
You can also add a panel tapped off of the feed-through lugs in your meter main -- they are the two lugs on the hot busbars visible at the bottom of your first photo. This could be an indoor or an outdoor panel, limited only by the 200A main breaker in the meter-main, although using a sub-200A feeder and panel for this would invoke the feeder tap rules.
As mentioned the simplest thing would be to rearrange breakers, with a 15-50-15 triplex you could be squared away quick and easy, but then you are dead full.
If you have additional work in the near future that will require a panel upgrade you might be better off doing that now, but I wouldn't go that way "just in case maybe someday" - no need to open that can of worms now.
Another possibility may be to use the feed through lugs to feed a fused disconnect, worst case you'd need to put the disconnect for the charger right by the panel.