How The University of Nevada, Reno Keeps Its Lab Running When The Power Fails (Page 4)
A pure sine wave UPS (Google trends now shows more commonly referred to as a battery backup) puts out exactly the same waveform power as you get from a wall socket, although it is usually much cleaner. As a comparison to water systems which are easier to understand, think of it as putting tap water through a filter and getting crisp, clear, clean water out. This is typically required for any electrical device with a 120 volt to 12 volt or 5 volt step down transformer (commonly referred to as wall wart), Active PFC power supply, Energy Star 5.0 or above rating, and sensitive instrumentation. Standard UPS systems usually have square wave, modified sine wave, simulated sine wave, or some other sub-standard waveform output as it keeps the cost of the uninterruptible power supply down. These lower quality waveform models are ok for most inefficient older electronics and non-sensitive equipment, but unacceptable for newer energy efficient electronics and precision electronics. As a comparison to water systems which are easier to understand, think of it as putting tap water in and getting grey water out, fine for watering plants, but not to drink.