I have enclosed my screened porch to create more living space(Florida Room). I am using a single zone mini split ductless heat pump for heating and cooling. It has been calculated that I need a 12,000 BTU unit. However, most of these units are available in 110 volts and 220 volts. The 220 models typically cost $50-100 more. I am trying to determine the advantages and/or disadvantages of each (power usage, unit life, ease of wiring, safety, etc.) in order to choose a unit. Any help is appreciated.

I am not sure the answer is always going to be the same. In either case, it should be on a heavy duty circuit of its own. If the unit is going to be relatively close to the breaker box, the 110 might be just as well. Does your box have 2 adjacent slots to accommodate the 2 pole breaker 220 will take? Who is doing the wiring? With a nearby, but crowded breaker box, it might be just as easy for you to run say a 10-2 with ground cable for 110. The installation instructions will specify the circuit breaker needed and maybe the wire gage. If you are buying 10' off the rack at Lowe's, the next wire size up may only be pocket change more. #10 is harder to work with than #12.

Adding a circuit isn't that big of a deal. If you have never done it, I can help. There are ways of dealing with a full breaker box too.

220 volts uses half the amperage of 110 volts. It the amperage that makes your meter spin (watts)(P = E x I) p= watts, E= volts, I= amps. Making the meter spin half as fast using a 220 volt model saves energy, and thus cost over the long term. If you have the space in the distribution panel, go 220 to save money, long term.

The cost of 240 volt versus 120 volt is only in the initial cost. A 2 pole breaker for 240 volts will cost about twice the cost of single pole breaker for 120 volts. (maybe $4- $10 more). Depending on the power requirements, the wire size maybe smaller for the 240 volts, thus balancing the difference somewhat. The actual cost of running the unit once it is installed is theoretically the same. The total wattage is the same either way. If you increase the voltage, then you will decrease the amperage, so watts will balance out either way. The cost is basically the materials to install. It shouldn't take an electrician any longer to install one versus the other.

Hi Maine Master and welcome your input is appreciated but you just answered a question that was about nine years old, check in the upper left corner for the date and have at it.

One thing I did forget, if the electrician can't install breaker(s) in existing service panel, the cost will be more because of the needed upgrade and that depends on a more complicated evaluation of your service and total home load which your electrician should be able to provide.

And, the only true saving with 240 is in wiring since you can use a smaller gauge wire.
Maine Master E-do the meters in your area measure amp hours or kilowatt hours? Never saw one that does so I'm not sure how Amperage causes the meter to spin faster. "Making the meter spin half as fast using a 220 volt model saves energy"? As noted Amps X Volts =Watts, regardless of 120 or 240.