NOPE!
Btu output is DIRECTLY related to Watt input period.
1 watt = 3.41BTU
So a 1500watt heater will give out 5114 BTU per hour. It doesnt matter what type of electric heater it is. The only exception is a heat pump. Because they dont "create" heat. They only move it. And they are about 3x's more efficent (depending on ambient outside temps of course). So at 3x's more efficent, a heatpump gives out 15,000BTU for every 1500 watts consumed.
And to further break it down, Propane is about 91,000BTU per gallon. With aberage prices at about $2.00 per gallon, you are getting roughly 40,500 BTU for every dollar.
With electric @ about 10cents per Kwh, electric is about 34,000BTU per dollar spent. And a heatpump at 3x's that you can get over 100,000 BTU for every dollar spent. That is why heatpumps, especially geothermals are so popular (at least in my area). Because they are far more efficent than any alternative. Unless you count burning wood and OWB's. But some people just dont have the capibility or time to cut 10+ cords of wood a year.