Heating attached garage?

What are my best (cheapest) options for heating an attached garage? My garage is under the house, 2x long and 2 car wide. It has a concrete wall in the center dividing the front from the back. I really need at least the back to maintain a reasonable tempt. Only the garage door and a small section of wall isn't in ground. The garage door really only gets opened when the Plasma table is running. A ventilation system is in the works so that isn't going to happen to be an issue in the near future. Initial ideas are just two of those oil filled heaters and leave them running all the time. Are there better options in the sub $200 arena? 

Wall heater on a hundred pound propane tank?

Is there natural gas in the garage? I’ve seen small cheap Reznor heaters on Craigslist that would work great if you can get gas and a vent to it. I guess with a $200 budget that would be tough though. In that range I’d say you’re on track with a pair of oil filled radiators but they take will a long time to recover from a garage door being opened. 

https://www.amazon.com/dp/B0000AXEZV/ref=asc_df_B0000AXEZV5311864/?tag=hyprod-20&creative=394997&creativeASIN=B0000AXEZV&linkCode=df0&hvadid=198093463189&hvpos=1o7&hvnetw=g&hvrand=11428471912608640555&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9018809&hvtargid=pla-348642391382

I have one of those little guys in my attached, insulated garage (only shares 1 wall and no roof space with house) and it works pretty well.  Warms from 0F to comfortable (40s?) in probably an hour, 0 to 65 in about 2 hours.  Really works great when outside temps are in the 20s and 30s, works OK when temps are lower.  I have a vaulted ceiling in my garage so I have a ceiling fan installed to circulate the air. that helps a ton.  

Ran me about another $60 a month to keep my garage at a constant 40 degrees a few years ago when I was supercharging my Corvette over winter.  

Its pissing in the wind in anything bigger than a 2 car garage, but I couldn't beat it for ease of installation for occasional use.  My buddy who is a professional HVAC dick uses one in his small garage, if its good enough for him its good enough for me.  

For my 1 1/2 car garage I have an electric heater,220V that heats pretty well.   For added heat in the garage door area I use a portable propane heater.

In reply to 93gsxturbo :

This is a good idea. I have access to 220 as I have the panel right there. My wife is concerned with open coils but if it is mounted on the ceiling, she would probably be ok. 

In reply to dculberson :

No gas at the house. It is geothermal so I don't have a propane tank either.

Geothermal? Check your manifolds at the unit to see if you can add another loop and just get a used room radiator to hook in.

In reply to oldopelguy :

Interesting, I didn't know that was a thing. I will check into it. I did find a unit like 93gsxturbo posted for $100. 5000w unit.

I have the same setup that 93gsxturbo Dork described.  But my garage isn't very big- 16'x24', and shares one wall with the house.  Exterior walls and ceiling are insulated, one overhead door and one man door.

My heater came from Northern Tool:

I only run it when I'm working out there, so I'm not sure on the cost.  But it was cheaper and easier to install than a small house furnace or a gas unit (no venting to deal with or gas lines).

Tap into the geothermal manifolds.  Run some 3/4 Pex out to 16' of baseboard and back.  The temp of the water is a little low on the Geo, but it will still do a decent job of heating the garage.  when its really cold, make sure it runs constantly so that it won't freeze, or at least keep the garage temps up above 50 all the time.  If the water keeps moving, it won't freeze.  You can run that loop on a wall thermostat.  Depending on the boiler controls and manifolds, you can get someone to install the whole thing for $1000 to $1500.  Do it yourself for half of that.  Running off the geo instead of electric or gas, will pay for itself in 2 to 3 years.  Wish I had geo.

I’d just run a loop off of geothermal. 

I also have a small 240V heater that is capable of getting my poorly insulated 1.5 car attached garage warmer than my house. It's a 4000 watt model from Northern Tool. A smaller version of this little guy.  If the panel is in the garage, adding a 30A plug should be easy and cheap.  If it has one downside, it's a bit noisy when running. 

Long term, the Geothermal loop might be a really great option. However, there is 3" of snow on the ground now so I need to do something soon. 

Being mostly underground, the back area shouldn't require much heat at all if it's well insulated. It's not the fastest fix, but getting it well insulated would mean you could probably buy a smaller, less expensive heat source that would run less often.