Rack Power Calculator
Estimate a server rack's IT load, facility load with PUE, cooling demand in BTU per hour and monthly electricity cost. PUE scales facility energy, not the equipment's own watts.
Result
| IT load | 1.20 kW |
|---|---|
| Facility load | 1.68 kW |
| IT heat | 4,095 BTU/hr |
| Monthly energy | 1,226 kWh |
| Monthly cost | $183.86 |
Note: Monthly figures use 30.4 days.
Learn more
How it works
Enter the power your IT gear draws, your facility's PUE and your electricity price.
- Facility load = IT load x PUE. PUE (power usage effectiveness) covers cooling, UPS losses and lighting: a PUE of 1.4 means every 1 kW of IT load needs 1.4 kW at the meter.
- Heat: nearly all the power a server uses ends up as heat. 1 watt = 3.41214 BTU/hr, the unit cooling equipment is rated in.
- Monthly energy = facility kW x 24 hours x 30.4 days.
Worked example
The default is a rack drawing 1,200 W, with a PUE of 1.4 and power at $0.15 per kWh:
- Facility load: 1.2 kW x 1.4 = 1.68 kW
- Heat: 1,200 x 3.41214 = 4,095 BTU/hr, about a third of a ton of cooling (1 ton = 12,000 BTU/hr)
- Energy: 1.68 x 24 x 30.4 = 1,225.7 kWh per month (shown as 1,226)
- Cost: 1,225.7 x $0.15 = $183.86 per month
What PUE should I use?
Use your facility's measured figure if you have it. Large modern data centers report 1.1 to 1.4. A server closet with a room air conditioner is often 1.8 or higher.
How big a circuit does the rack need?
In the US, the electrical code limits continuous loads to 80% of the breaker rating. A 20 A, 208 V circuit gives 20 x 208 x 0.8 = 3,328 W of usable power. Check local code and your PDU rating.
Should I use nameplate watts?
No. Power supply ratings are far above typical draw. Use readings from a metered PDU, the UPS display or the servers' management pages for a realistic figure.
Maintained by the RACKCRUNCH team. Last reviewed September 29, 2026. How we calculate | Report a problem