Not sure if this helps, but I came across this article while checking out radiant floor heating systems for my kitchen.
Low Voltage versus Line Voltage Radiant Systems

Posted By scatman on 25 Jan 2011 10:37 AM

I'm on a radiant heat driveway project. Wondering what is best for the application. Seems like low voltage would be more cost efficient.

Being an electrical engineer, I can assure you that the low voltage system is not more cost efficient to run.  It may be safer to deal with, or easier to install, but the efficiency of turning a watt of electricity into a watt of heat is 100%, as long as you are doing the transformation in the desired area, whether it is low voltage or high voltage.

However, the cost of changing one form of electricity (line voltage) into something else (low voltage) is not negligible.  Any reduced voltage application will suffer efficiency losses via the transformation from one voltage to another.  If the low voltage is 24VAC, or some other AC voltage, the losses could be smaller, but if the low voltage is 24VDC, or some other DC voltage, the losses could be quite large.  It's difficult to imagine why someone would go from AC to DC in what must be a resistor-type application, but stranger things have been seen.

Jeff

Electric radiant driveways (at any voltage) may be cheap to install, but is rarely the cheapest to operate. Whether it's worth it to go another route depends a lot on what else is available, the total amount of heat that you need to deliver per year/decade. An isolated hydronic loop off a gas-fired hot water heater or heating boiler can work, if available, and may make economic sense if snow & ice melting is need regularly throughout the winter, maybe not so much if it's only 1-2x/winter. But if you're paying very high rates for electricity it can still flip the other way.

Jeff has it right- from an operating cost point of view line voltage will always edge out low-voltage systems due to conversion losses going from line to low-voltage.

Driveway snow melting is not for the faint of heart. I have designs many systems over the years and have never specified cable. As suggested, you can't change your mind if you put electric cable in a radiant slab. If you install PEX tubing, you are all set with infinite boiler/fuel choices including electricity, oil, wood, propane and natural gas boilers.

I use high efficiency condensing boilers for most of the snow melting systems I design.

Naturally before starting the design on any heating or snow melting system, fuel sources must be considered along with the load and the Class of snow melting system you require.

Snow melting is a very specialized field within the exclusive hydronic field.

I'm not going to get into the differences between hydronics and electric as it was not the OP's request. I am, however, going to comment on the link provided that does all but curse low voltage systems. Making false claims only proves that there are distributors out there whose sole purpose in providing that webpage is to sell you what they have in stock.

Facts:
Low Voltage systems are ETL approved to UL standards. UL was the first company out there doing what they do. Competition being what it is, others are now doing the exact same thing to the UL standards that everyone became accustomed to. To make claims that anything but UL is something less than UL is just not stating the facts.

Low voltage systems are more efficient when the element can be installed closer to the surface than line voltage. If the element is closer to the surface you don't need as much heat to do the same job. So, 21 watts psf works great when it's closer to the surface. If you want to generate more heat because ASHRA says you should, go ahead. But it is a waste of energy. Look into what ASHRA's standards were that they went by and you will see why they state a higher wattage (btu) is required. If you bury the element deeper, you need to generate more heat to get through or it will not function quickly enough to prevent the snow from building. Line voltage is regulated by Code wher it can be placed. Thus, it requires more heat to function well.

Installed correctly, line voltage works as well as low voltage. They are similar installations in new pour concrete applications (except for depth of element required) but in asphalt, there are so many manufacturers restrictions that the extra costs to run out the asphalt far outweighs the extra material costs of low voltage installations. Further, since the low voltage element can be closer to the surface (as described), you will save about 20% of the running costs.

Generally speaking, quality elements don't 'go bad' if they are not damaged in shipping or on installation. 100% of the issues we have seen are either installation damage or third party damage, that's with low or line voltage. The line voltage manufacturers always include factory testing information for the element you buy that must be compared to as installation proceeds. By definition, if a single copper stranded insulated wire is damaged, it's obvious.

So, if you bury an element with a 10 year warranty you will get 10 years out of it, guaranteed. If you bury a 25 year element, you will get 25 years out of that element, guaranteed.

As mentioned, the low voltage snow melting element is a THHN rated copper stranded wire that is approved for being buried in asphalt, concrete or under pavers in a sand or mortar bed. We can provide the approval letters to show it. It is an AC/AC transformer and the loss is something less than 2%.

The reality is that after the installation is complete and the element is buried in concrete...etc.. if a zone is not functioning, it is almost impossible to dig a wire out of concrete or asphalt (low or line voltage) without damaging it while finding the original damage. So, how was it originally damaged ???... defect or damaged during the search...who do you think will win that one? All that matters is the repair itself. If the low voltage element is damaged, a standard tick tracer can find the break. A single butt splice and some heat shrink repairs it and MAINTAINS the 25 year warranty. IF you can find the break in line voltage, per the manufacturer, any repaired damage to line voltage elements voids the warranty on that zone. They don't want it repaired, they want it replaced.

That whole article is just sour grapes. Both systems work. Which fits the budget and who is there to back it up is what counts.

Warms is right!

If you have to use electricity, low voltage is the way and Warms is THE man.

If you bury it, you have a good start!

hhehehehee

Badger's only 1/2 right. We are both low and line voltage systems. I just don't appreciate internet distributors who don't allow the truth to get in the way of a good argument...

Here's a good low-voltage system. (FloorHeat)
There are other options too, with Zmesh being one of them.