A:Answer With a quick look at the I Mac specs, it appears that this will provide reasonable support for just the computer and monitor. It has a capacity of about 360 watts, (I Mac G5 = 180W) which should be adequate. The I Mac shows a frequency range of 47 to 63 Hertz, so the stepped wave form should not be too damaging. The UPS is an off line unit so "normal" operation does not use the inverter. That being said, there may be issues with the transition from utility to UPS power according to the ability of the I Mac to withstand a sub-second wave form disruption. This is a simple, inexpensive UPS. If you use the I Mac for serious use you may want an online, double conversion, sine wave unit, which is much more expensive. Home use is probably OK.