I am an Electrical Contractor. If you want to consider looking at going all electric in a residential area its easy to calculate how much power you are going to need, and how much you have available.
For heating loads it is simple Volts x Amp = Watts. So 220volts x 20.5amps = 4510 watts.
Your wife's curling iron is usually 1500 watts, so it would be 110v x 13.6a
It gets tricker for any motor, since motors dont use Power the same. Most small motors like transfer pumps are around 1/8hp and are 110volt @ 2amps.
It is always best to 220 volt motors and heaters. since they automatically use electricity from both Phases. If you have a 100 amp service to your house, you can not exceed 100 amps on ether of the 2 phases or the Breaker/fuse will pop. This means if you use lots of 110 volt equipment, you have to make sure you balance the different loads across the 2 phases.