In this system all loads are 120 AC and run through an inverter. This system could require more modules and batteries than a combination AC\DC system depending on the efficiency of the AC appliances. The recent development of high efficiency AC compact fluorescent lights have made inverter powered homes more practical. There are two advantages to this system: (1)A conventionally wired house is ‘inverter-ready’, . whereas DC wiring requires larger gauge wire and separate circuits. (2)Wiring costs are less and simpler for 120 AC. However, without any DC alternatives, a back-up inverter may be necessary. A small inverter could be a back-up to provide essential small loads like lighting and communication while the main inverter was being repaired. System cost may range from $3000 on up.