how many amps to my garage do I need?

we finally bought a house at the beginning of the pandemic... it has a nice oversized 2 car garage separate from the house but it has only a single 15amp 110v run from the main house and one pair of sockets (what a joke) 

we need to upgrade for more power so I'm going to have to run a drop from the main box from the house anyway... good time to run network and some other things anyway out there... so I need to know how big of a drop/sub panel box I need to put in the garage

the real question is how much do I really need?

the one extra I need most won't is a 30a 110 plug to the side of the garage for the in-laws camper... 

then I want to be able to run any future 220v tools I might get, at the moment I only have a 220v mig, but down the road I'd like to add an air compressor and 100% plan to add a/c down the road (yay houston)

I know I may need a larger panel on my house but I haven't gotten around to talking to an electrician yet but figured i'd get an idea of what sort of power setups GRMers are doing which I imagine is a little more demanding than most.

Absolute minimum would be 30A 220V.   I have 100A in the garage and then run another sub panel off that for the kids clubhouse.  They have a 30A 220.  It runs the lights, a couple of indoor outlets, and outside outlet, and a dedicated outlet for an electric woodstove looking heater.  If its just a regular garage and not a garage palace, then go with a 60A panel with at least a dozen knockouts.

You can run a split ductless off of a 20a 220. Figure another 220 for a welder, the camper needs 30...

I'd go 100A if possible. Leaves plenty of capacity. Campers and the A/c start can spike the power, nice to not worry about it. 

Do 100A. I did a 60A subpanel in the garage, and it's great for the outlets/lights, but I would love to get a "real" 220v welder, and many of those Essentially call for 50A breaker. It would be much more comfortable to do that with 50A remaining than with 10.

100A preferred; 60A minimum.  But it really will depend on the current service and panel at your house. 

If the house has natural gas, look into running a gas line to the garage as well for heating.  The trench would need to be a bit deeper, but it'll be cheaper to run both with one dig. 

I'm building a detached garage for a family.  They will only run probably a 50 amp service to the building.  (no special 220 service needs)

Noticed last night that Home Depot and Lowes don't even stock 60 amp panels anymore.  Local codes don't allow.

For $75 got a 100 amp panel with main breaker and some 20 amp breakers.

If you are doing it yourself, make sure the supply line is a large enough gage.  That's the biggest mistake I see folks make.

90A seems to be the sweet spot as you can feed with 2224 low cost rv feeder cable, bump to 100A you may as well do 125A and if you go that far... 

In reply to Purple Frog (Forum Supporter) :

What gauge supply line should a person use for a 100A panel?

I'm going to get running 50A 220v to my garage soon.  It's only a 1-car detached (but currently has the same 15A 120V like yours).

My plan is to use the existing circuit for the range and convert the range to gas.  For some reason in my house, they wired the stove with 4ga, so I could go bigger, but I'm also adding 30' of conductor.

50A will let me run my 220v welder or plasma cutter, and have enough left over for my air compressor.  Those are my only big current-users.

Another vote for you to go 100-amp.  It sounds like you're going to need it, and a little extra is always a good thing.

My builder ran a 50-amp sub-panel from the 400-amp service in the house to my detached garage.  Meets my current (!) needs, which presently consist of a 220-volt compressor, lighting, MIG.  Things might get a little dicey if I add a mini-split.

At some point, you might want to plug in a car. That's 30-50A right there. 

I've got 60 in mine. main is 200 house is 100, so technically I've got a bit of extra capacity on the main if needed. 

There's really only one of me working in there though, so the chances that I'm using the lift and the welder (for example) at the same time are low.

60 amps in the shop and have not felt the need for more in 10 years.

I've got a 100amp sub panel being fed by 2/2/4 gauge aluminum triple rated (Indoor, Outdoor, Direct Bury) feed cable.  It's actual only rated for 95 amps so I bought a cheap 100 amp panel and am running it behind a 90 amp breaker that feeds the sub panel.  That way if I had an issue on the feed line the 90 amp in the main house panel would pop first before the sub panel main breaker.   Locally available 80-90 amp sub panels only had 10 circuits.   To get a 20+ circuit one was going to require buying a larger panel and a replacement downsized main which was basically 2x the cost of a 100amp 24 circuit panel.  90 amp breakers are readily available and affordable.   So I used the solution I used.  It still protects the 95 amp rated feed line but I'm not 100% sure it's to Code.  We don't have inspections and I've spoken to liscenced electricians to confirm its safe so I'm not concerned.  

In my 1200 sqft shop (1000sqft main floor with 200sqft loft) I have use all the circuits available in the panel.  Between lighting, keeping total outlets per circuit to a reasonable amount, and providing distributed 220V power to all 4 walls of the shop add up quick.

As with many things like this:  more is better.

One consideration that you may not be thinking about:  What about the potential need in the future to charge an electric car?

Note, I am not an electrician.

Instead of branching off your house panel, go to the meter box and run a dedicated line from there. (After the meter, no cheatin') This takes the load off your house box and wiring, making the garage independent.

As far as size. Go big. It doesn't cost much more and you will save headaches in the future. Add a CAT6 line and 75 ohm tv cable while you are stringing stuff.

I keep reading this as how many amps do I need in my garage...band.   I’ll go now. 

Mine is a 50 amp service 220v, but I don't own any actual 220v things yet. The way I see it since I am 100% LED with garage lights and only use electric power tools (no big honking air compressor) so when I finally get my 4-post 220v lift I'll still be in the clear.

But like everyone else already said, I'd shoot for 100 amps if possible. Don't screw around on the wiring, make it right the first time. And don't skimp on the outlets. I've got them everywhere along the walls, I love it.

The gauge of the wire from the home to the shop depends on amperage you plan to use and length of the wire.  There are charts available on the interweb to help you out.  Usually I shoot for no more than 4% line loss.  The job I'm doing this week requires 120' of cable.   That garage will probably only only use 30 to 40 amps at peak.  Might be able to use 6 gauge copper.

Another consideration.  Realize that even if you put in a 100 amp sub panel in the garage, chances are you never use that much at any one time (especially if its a one man shop) because you are only using one tool at a time.  

I have a 50 amp RV outlet on the side of my shop that has a 100 amp sub-panel.  Now if both a/c s  were on in the motorhome, and the shop a/c is running, I'd have to be careful with the 220 welder., air compressor, etc.  But, while that particular situation is possible, it has never happened.  

Concerning number of outlets per circuit... in a one  man shop i push the number a bit because of the "one tool at a time" theory.   I have to remind myself that the current user may not be the user 10 years from now, so I fall back to the NEC guidelines.

Tanner brought up a great point that should be considered.  The future is coming, a big 220v port for vehicle charging is a huge consideration.  

Keith Tanner said:

At some point, you might want to plug in a car. That's 30-50A right there. 

The Canadian in me immediately thought, "But block heaters are only 400 watts."