Home / Glossary
UPS terms explained
Understand VA, watts, runtime, topology, batteries and power terminology.
A
B
battery capacity
Battery capacity describes how much charge a battery can store, usually shown in ampere-hours (Ah). It helps indicate potential energy storage, but it does not determine UPS runtime by itself.
Learn morebattery chemistry
Battery chemistry identifies the materials and electrochemical type used in a UPS battery, such as lead-acid or lithium-ion. It affects service life, charging, weight, and operating considerations, but does not determine quality by itself.
Learn moreblackout
A blackout is a complete loss of electrical power. In UPS and backup-power listings, the term describes the event the product may help you manage, not a rating of its performance.
Learn morebrownout
A brownout is a temporary drop in electrical voltage, usually without a complete outage. A UPS may respond with voltage regulation, battery power, or no special correction, depending on its design.
Learn morebypass
In a UPS, bypass is a path that can supply connected equipment without using the main inverter. It may be automatic, manual, static, maintenance, built-in, or external, depending on the product.
Learn moreC
C13
C13 is an IEC 60320 appliance connector commonly used as an AC outlet on UPS units and power distribution equipment. It typically mates with a C14 plug or inlet.
Learn moreC19
C19 is an IEC 60320 appliance connector used for power connections on equipment such as UPS systems and PDUs. It commonly mates with a C20 inlet.
Learn moreD
E
ECO mode
ECO mode is a UPS operating mode designed to reduce energy use when utility power is within acceptable limits. Its exact power path, transfer behavior, and operating limits vary by model.
Learn moreexternal battery pack
An external battery pack is a separate battery module that connects to a compatible UPS to add stored energy and potentially extend runtime during an outage. It does not automatically increase output capacity.
Learn moreH
I
J
L
N
O
offline UPS
An offline UPS, also called a standby UPS, normally passes utility power to connected equipment and switches to battery power when the supply fails. The changeover creates a short transfer interval.
Learn moreoutlet grouping
Outlet grouping describes how a product’s power outlets are arranged into physical or functional groups. The label may refer only to layout, or it may identify groups with different power behavior.
Learn moreP
power factor
Power factor compares real power used by a load with the apparent power supplied to it. A value closer to 1 generally means the equipment uses supplied electrical capacity more effectively.
Learn morepure sine wave
Pure sine wave is an AC output waveform that closely follows utility power. It can be important for equipment that requires, or works better with, a smooth and consistent waveform.
Learn moreR
rackmount UPS
A rackmount UPS is an uninterruptible power supply designed to be installed in a standard equipment rack. It helps keep connected equipment powered during outages and power disturbances.
Learn morereplaceable battery
A replaceable battery is a battery designed to be removed and exchanged instead of permanently sealed inside the product. The label alone does not show how easy replacement is or which battery is required.
Learn moreruntime
Runtime is how long a UPS can keep connected equipment powered from its battery during an outage. It depends on the connected load, battery capacity, and operating conditions.
Learn moreS
T
THD
THD, or Total Harmonic Distortion, measures how much a UPS waveform differs from an ideal sine wave because of harmonic content. It is usually shown as a percentage for output voltage or input current.
Learn moretower UPS
A tower UPS is an unmounted, upright uninterruptible power supply designed to stand on a floor, desk, or shelf. “Tower” describes its physical form, not its runtime, capacity, or power quality.
Learn moretransfer time
Transfer time is the brief interval a UPS takes to change from line mode to battery mode when utility power changes. It is usually measured in milliseconds.
Learn moreV
VA
VA means volt-amperes, a measure of apparent power. It describes the electrical capacity a product can handle, but it is not the same as watts, which measure real power.
Learn morevoltage sag
A voltage sag is a temporary drop in incoming electrical voltage. In UPS products, it describes a power-quality event that may be corrected, supported, or passed through depending on the unit’s design.
Learn more