If it’s going to stay as a “garage” regardless of what you might actually use it for, you can’t tie it into the ductwork of your home.

There are lots of ways to accomplish what you want. At the high end of things is a mini-split system (some also heat). You could also use electric baseboard or a gas (some are ventless) heater plus a thru-the-wall A/C unit. All depends on what you want to spend, how you want it to look, and how you use the space.

If the walls/attic space/doors aren’t insulated, you might want to think about that as well.

Thanks Mike. We don't have forced air heat.....so not an option to tie in and achieve heating anyway. Yes ceiling, walls, and garage door are insulated. Any guesstimate on costs of a minisplit? Does it need a 220 line to work? Electric baseboard could be 120? I will have an electrician do any wiring. I am just wanting to know options.

I presumed that you have central A/C in the house, you can’t tie into that. The reason is that if a car is left running in the garage the fumes could get pulled back into the house.

No idea what a mini-split system costs - depends mostly on size. You will need at least one 220v circuit for whatever you end up doing. 120v just doesn’t provide enough power for any significant level of heat, unless you have a very small garage. There are small “window” A/C units that are 120v but I’m guessing you have at least a two car garage...

If budget allows, I’d suggest taking a good look at a mini split system.

There are minisplits that can operate on 120v. There are also heat pump versions. I would not put a gas flame inside a garage.

Maybe you should look at a through-wall PTAC unit, like you see at a motel. Not as sophisticated as a heat pump, but you can buy one for less than $1,000. Heat is electric resistance and cooling is conventional AC. Can hard-wire or plug in to 230v.

We have a Mitsubishi mini split for garage & shop space, it does both A/C and heat and works very well (Mid Atlantic temperate climate).

Prior to that we used a window unit air conditioner and electric space heaters If needed.

I don’t know that a mini split would be the cheapest, but I think it would be your best solution for the space you have and your goals. The upside is the install will be less complicated given you will perhaps have less constraints for where the indoor and outdoor units will or can go. But you will need a pretty large one given your sq footage, But I’m assuming you won’t need multiple zones. But again, I think this would be the best solution, but not the cheapest.

Thank you all for the feedback!

What climate are you located in? Do you want to keep this conditioned 24x7 or only when you use it? How often will you use it?

If you'll be creating much dust or if air movement is an issue for anything you'll be doing in there then consider in-floor hydronic for heating. No filters or other stuff to get clogged up. No air movement to cause problems for finishes or other stuff.

Then mini-splits for cooling.

You are not going to get good advice unless you describe the climate you live in.

for 1000 sf a heat pump is a reasonable solution for heating and cooling in climates south of the sub-arctic. If you don't need the "split" aspect of a mini-split you can save a lot of money.

I am on the bandwagon with most of the other responses. Without knowing where you are, my generic answer is a ductless mini-split with heating and a/c. Use only when needed; completely separate from rest of house; controlled environment. Easy to install. https://www.fujitsugeneral.com/us/residential/what-is-a-mini-split.html