Generally, if you have a normal 110v going to a breaker panel, you already have 220 capability. In a normal install (althought it is called single phase), you have three wires, two hot and one neutral. this is actually two phase. If you look inside the breaker panel, you'll see two rows of hot lugs (black wire) and one row of lugs (neutral- white wire). This is so you can balance your 110 load across phases. To get 220v, you just tap across the two "hots." So if they come in with 3 wire power, you have 220 capability, you can add 220v circuits now or later. If they only come in with two wires, beware, that usually is bad sign.
