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or below a safe range—including extended brownouts. ANALYSIS
An EVR does not supply power and cannot compensate In the following analysis, we compare the total owning
during periods of total power loss (blackout). Rather, they costs of two backup power options. The total owning cost
compensate for voltage sags, swells and brownouts. is comprised of two figures: the initial purchase price of
But used in conjunction with an existing generator and/ each piece of equipment and the yearly running cost of
or UPS, which provide blackout ride-through, an EVR is a each piece of equipment.
safe, reliable and money-saving way to ride through daily,
weekly and monthly power-quality issues. And EVRs have OPTION A depicts a system that has, for the past quarter
industrial-grade durability, an unlimited life span, and no century, been applied to mitigate power anomalies.
moving parts to maintain. Option A relies upon a UPS to provide sag and surge
protection and to supply full power to sensitive and critical
loads (~15%) during brownouts. It also relies upon diesel
generation to power essential services, such as HVAC,
refrigeration and elevators.

OPTION B supplements Option A with an EVR, which Initial Cost:
allows the system to remain at full power without diesel
backup during power surges, sags and brownouts of any Generator $320,000
duration. The addition of the EVR not only reduces reliance UPS $87,000
on diesel, but it also reduces wear and tear on the UPS. Total $407,000
Because the EVR will compensate for all surges, sags and
brownouts, the UPS will have fewer on/off cycles and less Yearly running cost:
required maintenance.
The cost of a diesel generator running at ¾ load is
approximately $630/hour. This figure assumes that diesel
OPTION A: 1200 KVA SYSTEM as designed, with a 200
KVA UPS system deployed to protect critical and sensitive fuel costs a conservative $10/gallon delivered and .07
loads, such as sensitive computing equipment, and a G/KWH. The annual cost for UPS maintenance, battery
1200 KVA diesel generator to power essential services. In replacement and cost of losses is estimated at $21,300
this option, the generator control is set to initiate when the per year.
local voltage drops below 90%.

INDUSTRY JOURNAL 21