I have a building in which I am going to replace 9 3ton units. There is 3 phase in now but my tech suggests single phase. My clients pay for their own electricity. These machines have been in service since 1989. The cost of the single phase is about 700.00 a unit less. With today's efficient single phase will the client notice a drop in their electric bill with same use? Also will the longevity be the same? My tech also says that repairs down the road will be cheaper with single phase. Both machines are for commercial use.
3-phase is slightly more efficient, but not nearly that much for units like this.
3 ton is a very small unit for central air. It is HIGHLY doubtful you (or a tenant) will see any noticeable difference in their bills.
Considering the dramatic difference in cost ($700 less), it's a no-brainer to go with the single phase units.