Power Quality and Power Reliability: UPS vs. Standby Power Systems

There is a lot of discussion lately about UPS and standby systems (and, no, we are not talking about methods of package delivery or airline flight status). Given the shaky state of the power grid, climate change induced weather events and a greater demand for electricity both in the U.S. and globally, power quality and power reliability have become major issues for commercial as well as residential customers. 
Uninterruptible Power Supply systems, commonly referred to as UPS systems, can filter incoming power to protect against electrical "noise" such as spikes or transients (i.e., a type of pulse caused by factors such as lightning, switching surges, or kick-in of large motors), thereby improving power quality in our increasingly data-driven world. The need for UPS systems is particularly acute for data centers, office server rooms and telecom equipment spaces, or any computer-intensive environment. Typically, UPS systems also have batteries to ride through power outages, but not the kind of batteries found under your car hood or inside your cellphone, as the former are more sensitive to extreme temperatures and much more costly.
On the other hand, standby power or "back-up" systems, of which the most common type is a generator, are not battery-driven but run on engines fueled by gasoline, natural gas, propane or diesel. The duration of generator operation is limited by the amount of available fuel. Standby power systems are so-called because they operate upon loss of utility power making them valuable to businesses and homeowners alike.
The primary difference between generator and UPS function is that the system or load being powered by a UPS never knows that power is or was lost. With a generator, there is a delay between loss of power and start-up so that critical equipment such as computers will power down and must be restarted, which is why a UPS is often necessary. However, for household items and most commercial systems, for that matter, a stand-by system can come to the rescue.
And, now, you understand the essence of UPS systems and standby power systems.