According to TURTLE :

Turtle, I'm not contradicting you, I just thought I'd extend your answers
a bit.

Yes Electric company want to talk in KWH and not in amps. You can covert amp to KWH if you like for they are
directly convertiable.

Not quite - power factor etc., but, given otherwise identical appliances on
120V versus 240V that behave exactly the same way, power factor going to be
the same in both cases, and thus irrelevant.

So I see no difference in the cost being lower for 220 volt service verses
120 volt service.

Exactly: the same unit at 120V and 240V is going to consume the same amount of
power - the latter at half the amperage and double the voltage of the former,
and thus the same Kwh consumed.

But there are _some_ differences, whether the differences are significant
enough to matter depends on many things.

The 120V vs. 240V line-loss isn't necessarily insignificant, even well
under circuit capacity.

Ie: given the exact same wire-size between a 120V and 240V circuit
(which'll be often the case with a window-mount AC), the 240V circuit
will lose 1/4 as much power to supply line losses as the 120V circuit
does. At, say, 120V/10A with a circuit long enough for a 3V voltage
drop, that's 30W at 120V, but only 7.5W at 240V. 30 hours of that at
120V is about 1 Kwh of lost-inside-house-walls power. 8-16 cents/day,
vs 2-4 cents/day. That may or may not be significant depending on your
own personal criteria.

There is also a second effect - higher percentage-wise line losses mean
longer startup (when the current skyrockets for a brief time) surge.
Which represents increased stress on the motor and potentially decreased
lifetime. But usually not significant enough to matter - even on
AC compressors where the initial startup is about as hard as it gets.

[It'll be seldom possible to use a smaller wire size for a 240V
circuit on a window-sized AC. If it'll fit on a 120V circuit,
the minimum wiresize at 240V is (usually) the same size anyway.]

It's probably also true that those companies building 240V units
are engineering for a different market than the typical consumer.

The typical consumer wouldn't be able to use one because it doesn't
have a 120V plug.

Thus at 240V there's probably fewer models available, but generally higher
true efficiency and longer life, because these are slightly more
"commercial"/"industrial" in intent. At a higher cost of course.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.