I have a 3 car garage that I am planning to keep heated this winter. which will be cheaper in the long run as far as energy costs. I have already insulated the garage and the doors.

Wow, I'm not trying to be argumentative, but at least in my area Electric heat is much cheaper than gas. In fact I'm getting ready to replace my 80,000 lp furnace with 18 KW of electric.

I'm not sure what your per KW rate is in your area, but you definitely want to measure out both types and do a calculation before you decide. Call your utility companies and ask them the rates per measured unit of energy that they charge.

As I said, here in Indiana, electricity beats gas hands down.

I have a 24x24x8 garage, walls insulated-no sheetrock. Ceiling insulated, insulated doors.

My hope is to be able to heat my garage so it is warm enough to do hobby work, and play with my children.

In Massachusetts, so the temp can get pretty low. I might need to raise the temperature by 30 or 40 deg.

I want the cost to be reasonable, for example, less than $300 preferably, unless there is a good reason or advantage where I can justify it.

I do not have natural gas and do not want a 100lb LP tank outside.

It needs to be reasonably sized, for example maybe 2'x2' max. Ideally it would be portable so in the summer I can store it somewhere else.

So far in my research I am leaning towards a Kerosene heater, due to the size, price, btu's, portability, etc. I am not sure if there are any safety or legal concerns.

Propane might work, but I believe I have to run a line to the outside even with a 20lb tank legally and safely.

Thanks so much.
I have oil heat, hydro air in the house.

The electric units, looking at them, basically all the ones you buy that are portable are 1500watts, is that going to be enough to heat this size garage?

I bought a small kerosene heater a few years ago when the natural gas line going into the small town where I live froze. I needed to temporarily heat my house (~2000 square feet).

After carefully studying the box for about a half hour at Home Depot I was amazed to learn that it DOES NOT need to be vented. Its a unit of less than 2feet wide x 2feet long. It's a little taller than 2 feet high. Its white with a chrome colored cage. Might have been Lowes, but think it was Home Depot... and I've seen it there again recently.

This thing kicks out some SERIOUS HEAT. It will handily heat your garage. During our gas outage, I placed the unit in the kitchen and it did a great job of heating the nearby family room too. It's an uneven heat, of course, so the kitchen was like 80 degrees (within a few feet of the unit) and the family room 65-70.

There is also a wick that supposedly needs periodic replacement. I've used the unit in my garage several times a year since for the past 4 years and have yet to replace the wick. I've seen the replacement wicks at Home Depot for about $10 or so.

Keresene is running about $3.50 a gallon where I live. You'll have to find a gas station that supplies it, and get yourself a 5 gallon blue keresene container. A single filling of the unit (which is probably a gallon or two) will keep the unit going for many hours... say 6 to 8. Sorry I dont have more precise figures on this.

When doing a project in the garage in the winter, I will typically fire the unit up a half hour ahead of time. Then the garage is toasty warm. On a number of occasions I have had to open the garage door a crack to cool the room down some. Very happy with this heater and its nice to have as a backup heater for the house too.

Good luck.