ECN Forum Forums General Topics of the Trade General Discussion Area Voltage Drop - 14 amps in 100'

On a resistive load, the effect of voltage drop will be less voltage applied to the heater load, which will reduce the total wattage of the heater.
In your case, the 4.4% voltage reduction would simply reduce your heater output to 1512 watts. On a motor load, low voltage will likely cause motor starting problems, and premature failure.
Remember that circuit components for electric heat often have to be sized at 125%, per 424.3.