I am getting ready to buy baseboard heat for a 800-900 squarefoor open area, old GArage, And I am looking at 3 8' 2500W sections of base board. is this enough. And How much better is the units you have that have the liquid in them

First, those of us on FixYa don't sell any products or appliances. Just information.

But to answer your question about electric baseboard heating ... It's the most inefficient and costly heating source you could use. With that said, a lot depends on the cubic footage of the area, as well as how well that area is insulated. This applies for electric, gas or oil heating. You rae not just heating square footage, you're wanting to heat cubic footage (i.e. Width x Length x Height = Cubic Footage). Assuming you have an 8 ft ceiling, the Cubic Footage would be (assuming a 9 ft ceiling) 7200 Cubic Feet. Based on that and if it was my home, I'd be installing a 20,000 - 25,000 Btu Vent-free (Flue-Less) Gas Heater, with built-in thermostat control. It could either be as a Free Standing, Vent-free Gas Fireplace System or simply a Wall Mounted Heater. One is decorative, as well as efficient and the other is simple and efficient. Plus, gas heat is a warm, moist heat that you feel very quickly and it's more comfortable than electric or oil heat. As a matter of fact, Vent-free Gas Heating Appliances are 99.9% efficient. And will work without electricity. Which is great during a Winter power outage. If you currently don't have Natural Gas at your home, then LPG (Liquid Propane Gas) is readily available.

So, by now, you figured out that my preference is gas. I have three Vent-free gas heating appliances in my 3000 square foot home (2-Vent-free Remote Controlled Gas Log Sets in existing wood burning fireplaces & a Vent-free heater in my 2-car garage). Our primary heat source is an electric heat pump. Which doesn't work well, when the temperature reach 32 degrees F or lower. We use the gas heaters only as a supplement heat source or as primary source, if the power goes out.

I hope you'll take a little time to research this, because in the long run, it can save you $$$. Below, is a link to Empire Comfort Systems. They have excellent supplemental and primary heating products in all looks, shapes and sizes. This will give you an idea of what's out there.

http://www.empirecomfort.com/corporate/

I hope all of this helped you. Please let me know. Thanks.