I am under the impression that, as a general rule, 110v heating and cooling options are inherently not very efficient. So I was surprised to find a 120v mini split shopping around with a fairly decent SEER rating (22). I'm fine hiring an electrician to put in a 240v circuit for me if I need to, but if this lets me save that money without significant downsides, why not right?
So for long term energy efficiency, is a 110v mini split an inherently bad idea?
Best Answer
The issue is not, generally speaking, efficiency in the sense of SEER or similar ratings. Using 240V instead of 120V allows for more efficient use of wire (12 AWG wire can handle 20A @ 120V or 20A @ 240V), and in some cases more efficient motors. Even higher voltage makes it economical to send electricity long distances, but that is really a different issue.
So the big question becomes, how much power do you need. If a device only needs something on the order of 1,500W, a 120V circuit is good enough and has the advantage that we (in the US) have them "everywhere". If a device needs more than 2,000W, a 240V circuit almost always makes sense. For example, a 5,000W appliance will use 21A when running, a 30A breaker and usually 10 AWG copper wire. The same appliance on 120V will use 42A when running, a 50A breaker and much more expensive 6 AWG copper wire (or possibly larger but cheaper aluminum).
But generally speaking, you don't need to worry about 120V vs. 240V too much, unless you are in a (rare, but they exist) 120V-only building. In most cases, start with:
and you will likely find yourself in a small system (120V) or a big system (240V) or in-between where you get to choose depending on other factors.