Thanks that is what I meant BTU / HR
Your numbers work out with my first attempt.
I found another website describing the heat output of cable heat electric flooring with a 3" standard spacing to be 34 BTU'S per square foot.
Rather than trusting this site the cable heat kit I'm going to use is from Warm Tiles (DFT 2065 60-70 sq feet 3.3 Amps).
Can you covert Amps to Btu's per hour? Just found this thread (http://forum.onlineconversion.com/showthread.php?t=421) online...
"Btu is a unit of energy not power, not sure why you would need Btu values. Usually things like backup power supplies are rated in Watts or kilowatts.
But here is how you would do it.
Amps * Volts = Watts
Watts * hours = watthours
watthours * 3.41214148 = Btu
So you would need to know amps, volts (usually 120 or 240), and the number of hours."
With this math I get 3.3 Amps X 240 Volts = 792 Watts
792 Watts x 1 hour = 792 Watthour
792 Watthour x 3.41214148 = 2702 BTU
With the rate of 34 BTU's per square foot I get 2210 BTU's
Which one is right?