Doug Miller wrote:
In article , indago wrote:

If the heaters are not too far from the panel, say more than 50 feet of
wire, you can use the 12 gauge wire, using just one circuit for both
heaters.

2000/220 = 9.1 Amps 1500/220 = 6.8 Amps 9.1 + 6.8 = 15.9 Amps

Not so fast. If the heaters are rated at 220V as he stated (not 240V) but his
service is actually 240V (as is very likely), the currents will be almost 20%
higher (10.8 and 8.1 amps, respectively) for a total of 18.9 amps, requiring a
30A circuit because...

Think about what you are saying, Doug. A 2000 watt resistance heater
stays a 2000 watt heater no matter what the voltage applied. Same for
the 1500 watt heater. The resistance stays the same. Only the amps
and volts are variables. The higher the volts, the lower the amps.
Indago's calc was correct, as he figured it on the (worst case) lower
voltage. One 20 amp circuit is sufficient for both baseboard heaters.