Do you need a portable or will it be a stationary shop unit? Do you have 240VAC available to run it? If not you are limited to no more than a 5 or 6hp motor due to heavy start up draw. The direct drives are generally smaller and cheaper, IMHO, a belt drive with a capacitor start motor and cast iron pump is a better choice. Avoid the Asian built cheapies, there are no parts or service available and they use odd air fittings. Vertical takes a lot less floor space than horizontal but it is a matter of preference.
Change the pump oil per the instructions, drain the tank regularly, and you should get years of service from it. Replace the tank drain petcock with a pipe elbow and ball valve to save some grief.
Ingersoll-Rand made some good units for home use but recently sold that division to off shore interests.

I would recommend you stay away from the direct
drive units, I think they call them "oil-less".
They are so noisey, they'll drive you nuts if
you are working anywhere near them. Also, many
will tell you 100psi is plenty. Well, I've had
several impact wrenches over the years and 120
psi is much, much better for them. And as far
as CFM, look at the requirements of the equipment
you will be using and make sure your new compressor
meets those air requirements. I have an air
drill that uses a ton of air and the compressor
I have now just won't keep up with it, my next
compressor will. Good luck in your search and
let us know what you wound up with and how much
you like it. See ya.

Will this meet my needs? Saw on TSC web site.

View Larger SKU Number: 3300700

Air Compressor; 26 gal Capacity; 1.8 HP; 150 PSI (Max)

Detail DescriptionTechnical SpecificationsWarranty InformationDetail Description
150 max PSI 4.9/6.3 SCGM @ 90/40 PSI. "Low rider" design has a low center of gravity that prevents tipping over. Pneumatic tires for easy transportation to jobsite. ASME certified tank.

26 gallons will not run an impact or air ratchet for long. You will spend a lot of time waiting for the tank to refill. 150psi sounds good but most of the time you need volume, not pressure. The machine will work hard reaching that high. Most air tools only need 90-100psi, higher pressure is not safe, but lots of volume.

Thomas and Rolaire (sp?) make some of the better compressors out there. The Thomas' are made in the US if that matters to you. Overall they seem to have the best combination of quality and capability but they are more expensive.

I would guess you would want something that can deliver at least ~4CFM maybe 5 or more. Of course that could vary depending on how much you are using the tools. Some tool manufacturers have good specs to help you size your compressor. I read where someone had a 5hp, 20gal compressor that was just big enough for their impact wrench, but I do not know what CFM it delivered. If you are shopping for compressor, make sure you are comparing apples to apples. Some manufacturers give their volume as displacement. Displacement measures volume with nothing between output and the compressor. Delivery puts all the hose and connections in between. For example, the Thomas T-200 displaces 8CFM, but delivers 4.6CFM.

Oil-less typically do not last as long as the oil lube compressors. They are usually both lighter and louder than the oil-lube equivalents.

You will have to decide between electric and gas, although most will do just fine with electric. If you need to work at a distance from your electric outlet, add hose length before extension cord length. The motors draw alot of amps. Almost all will run on a 15 amp circuit but they don't leave alot of room for other loads.

Sometimes you will need a little extra pressure but that would be the exception.

If you plan on a impact gun, you will probably need around 5-6 cfm at 90psi and around a 30 gallon tank if you dont want the compressor running every second you use the gun. First find out which tool will need the biggest cfm requirement and plan your purchase around that. Oil less units are not that bad. My craftsman 30 gallon 150 psi oil less compressor is going on 5 years with no problems. Its loud, but I keep it in the garage. If the temps get cold in the winter, you won't want to store a oil filled unit in a unheated area. My 30 gallon compressor is a little small for running my die grinder. The compressor is just about constantly running to fill the tank, but it always procduces enough cfm to keep the die grinder working. I just stop every couple of minutes to let the compressor cool. I don't use my die grinder that often so its not a big problem. This compressor keeps up with my impact gun, air rachet, air hammer, framing nailer, finishing nailer etc. This compressor is a little heavy for going up and down stairs, so I bought a cheapy UST 4.6 gallon oil filled unit for my basement. I paid $80 at Pep Boys. I think it has 3.8 cfm at 90 psi which can run my framing nailer and my finish nailer with no problems, which is the reason I bought this one.

Rollaire-Hustisford Wisconsin.

Go find a shop that sells air compressors as garage and auto body equipment. Tell them what you need the compressor for, and how much you will need it, and anything else you will need. Those little air compressors on wheels are toys! And, like some others have said, those little ones just can't keep up with any air tools, especially impact wrenches, etc. Waiting for a little cheap compressor to build up enough to take 5 wheel nuts off, is time consuming, and also tends to make ya learn some new cuss words! And also makes ya wonder why ya didn't take the experts advice, and buy a bigger, more powerful compressor. And, get the vertical one, stick it in a corner, aand have lots of room. Nothing worse than having a compressor banging away right behind yer back, when yer working on something, especially yer car or truck!

If you get a good 400 ft lb up double hammer impact a true 2 HP on a 20 gallon tank will work fine. No sanding though.
If you properly size your compressor the tank is almost an afterthought. We try to size compressors 40% larger than the tools used. For a home ower that is not always possible due to size and budget constraints. A large tank is good for a surge of air but brings nothing else to the table. Tis simply stored air. Having a 50/50 to 60/40 duty cycle keeps the air temp lower, increases the life of the pump and helps control water production.
Belt drive cast iron oil filled are the best.
As for the Thomas advice that was good a couple of years back but things have changed. Just shop parts for a Thomas and you will see what I mean. We used to sell the piston kit for the Thomas oil less for 49 bucks now our cost is 199 so we dropped the line. A few companies are buying up others and the result is not pretty like when DeWalt (Black and Decker) bought Emglo. That used to be a fine machine but those days are over.

Everyone has posted good info.
Here is some tidbits i learned in my quest:
-the Oil-less Colemans are not a sealed cylinder. mudbugs build a nest in the cyl and that destroyed the cylinder.
-with 10gal tank, airgun only runs for a few seconds before the pump kicks in again. A 6CFM pump takes a few min to refill the tank.
-I got the Harbor freight 30gal 12CFM 240VAC for $399.

Thanks for the info on the Thomas. I still read good things about them but their biggest downside being their cost. I had not read about parts pricing.

There were some moans over the DeWalt buyout of Emglo. People thought the product suffered from that. Though they seem to think they are improving now.

I don't know much about Ingersoll-Rand.

People always seem to speak highly of Rollaire.

The best comments seem to go to older compressors before this or that happened to whichever company.

Depending on your usage, you may be better off getting a decent disposable unit like a Campbell Hausfeld.

Thanks for all the valuable advice. I am still pondering on the 120vs240 set up. Can wire and run the higher voltage. May be an over kill though. Currently narrowed to:
1. Husky26gal,#VT6315,135MP,6.5/5.5 @ 40/90PSI,oiled belt
drive @ HD
2. Kobalt 30gal,oiled belt dr, #KLA1683066,1.6 HP,
155MP,6.5/5.5 @40/90PSI @Lowes
3. Campbell Hausfield 3.2hp,135MP,60gal,#3310006,
10.2/11.5@90/40PSI,twin @TSC
4. Eagle 3HP, 25gal, 5.6@90PSI,oiled belt dr @ TSC
5. Farmhand,20gal,2HP,oiled belt dr,20gal,5.5 @ 90PSI @
TSC
6. Craftsman,25gal,2 stage 1.6 HP,oil free direct drive,
5.6/5.1 @ 40/90PSI 175MP # 0916778N @ Sears
All are 110/220 and vertical. This is in no way final. All except the CH unit are mobile. Hoping to purchase in the spring unless a can't let it go sale comes along before then.

Do your self a favor and avoid the oiless compressors.If for no other reason then the noise they create.I have a Craftsman 1.8hp 25 gallon Pro model.I bought it last winter during a 20% off all tools sale they were having.Well worth the extra money it is quite.Check out its specs very impressive.Plenty of compressor for impact and air ratchets.This one out does my upright staionary 40 gallon shop compressor.

Here is a link that might be useful: Craftsman