240 is the preferred voltage because the efficiencies are better and the generator is load balanced.
If you need to have 120 volts, as well, then a balancing transformer to transfer power from one side of the 120 to the other side of 120, Xantrex sells a transformer but it is expensive.
A cheaper version is to get an auto transformer 230/115, open it and get the three leads,
- line,
- line and
(neutral),
take the center lead = 115 volts and connect it to neutral of the load wiring,
then the 230 line goes to one 115 volts
and the (neutral) of the transformer goes to the opposite 115 volts,
Make sure that the (neutral) of the transformer is not connected to the body of the transformer, if it does you need to separate the connection.
The same size KW auto transformer than the Xantrex will cost much less than half their price.
Nando