I am building a log home this summer and considering radaint floor heating. I have been considering a hydronic system, but resently came across low voltage systems. Low voltage looks good and easy to install .  The question that I need to know is how is the operational cost compared to hydronic using a propane boiler. 

Does anyone have experience with low voltage system and wind power or Photovoltic?

You don't need to look at other projects costs; that doesn't tell you one single thing about your particular house. Our industry is literally littered with "my last house cost blah" and "I am paying half of what my neighbors pay" and other such useless anecdotal info; it doesn't help at all.

Figure your heat load in BTUs per degree day, multiply by degree days for your area. that's BTUs/year. As warms noted, it's very tricky calculating this number for log homes and it's a necessary first step before you install ANY heating system if you want good results.

Electricity of any kind meets that load at 3412 BTUs/kwh. multiply by your kwh pricing.

Hydronics, it will depend. If you get a very high efficiency system (low temperature, modulating/condensing boiler) it could be up to 99% efficient but you are mostly likely to be in the low to mid 90's. for estimation, divide your load by your estimated efficiency (90% would be divide by 0.9). Divide the new, larger BTU count by 92,000 for the BTU content of a gallon of propane. now you are at gallons of propane, multiply by your propane cost.

and you have a ballpark estimate of yearly heating costs. All assuming the systems are installed well; and this is ballpark, wide ballpark anyway. on any home a heat load calculation is an educated marker but not a perfect prediction... more so on a log home.

as a nod to warms, I will note that the competence of your hydronic installation will affect the hydronic number a lot more than the electric system. so if you are working with an installer you are NOT confident in, you might run those numbers for a lower efficiency estimate and see where you are at.

In my area, northern NJ, electric is about 3 times the price of natural gas. If electric is only 20% more efficient the choice is obvious.
I understand the price of electric in other parts of the country is far less expensive then what I pay.

Wind and solar are years away from being viable for heating. Price per therm electric vs. propane and use hydronics so you can change your mind when electric goes through the roof.