LoadCairn / Facility efficiency guide
PUE & DCiE calculator guide
Review how the LoadCairn planning calculator compares total facility power with IT load, what its optional annual estimate assumes, and where the calculation stops.
Calculation method
Power inputs / planning only
- PUE = total facility power ÷ IT load
- DCiE (%) = IT load ÷ total facility power × 100 = 100 ÷ PUE
- Non-IT overhead (kW) = total facility power − IT load
PUE compares facility power, the numerator, with IT load, the denominator. In this calculator, DCiE is the reciprocal percentage calculation shown above; it is not a separate benchmark claim.
Illustrative example · not a target or industry benchmark
500 kW facility ÷ 400 kW IT = PUE 1.25
400 kW IT ÷ 500 kW facility × 100 = DCiE 80%
500 kW facility − 400 kW IT = 100 kW non-IT overhead
These match the calculator’s editable starting values and demonstrate the arithmetic only.
01 / Inputs and assumptions
Match the measurement basis
The calculator uses entered power values for a planning comparison. Its optional annual energy and cost estimates extend those inputs with fixed assumptions.
- Enter positive total facility power and IT load values in kW.
- Both power values should use the same measurement interval and facility/IT boundary.
- IT load cannot exceed total facility power.
- The optional annual energy estimate assumes facility power stays constant for 8,760 hours, with no leap-year adjustment.
- The optional annual cost multiplies that energy estimate by a constant, energy-only price per kWh.
02 / Limitations
A planning estimate, with boundaries
- The calculator cannot verify that the entered measurement intervals or meter boundaries match.
- A power-based calculation is not an energy-metered or audited annual PUE.
- The annual estimate does not model seasonal or load variation, demand charges, taxes, or other tariff terms.
- The result is not an engineering design, equipment-selection, or compliance result.
03 / Further reading
PUE source references
These references discuss PUE and its measurement. DCiE on this page is the calculator’s reciprocal calculation.
- The Green Grid, “PUE: A Comprehensive Examination of the Metric”
Defines PUE as an energy-based data center efficiency metric and describes measurement guidance.
- ENERGY STAR Portfolio Manager glossary: Data Center PUE
Describes data center PUE using total annual source energy divided by annual IT source energy.
04 / Run an estimate
Explore your own inputs
Adjust facility power and IT load in the browser, then review the calculation trace and planning assumptions.