The one-line says kW. The transformer is rated in kVA. Enter the real power and the power factor of the load and get the rating, plus the next standard size.
Enter power factor as a decimal (0.9) or a percent (90). Phase only affects which standard-size table is used.
Formula
kW is the power that does work. kVA is the power the wire and the transformer have to carry. The gap between them is the power factor.
kVA = kW ÷ PFkW = kVA × PFkVAR = √(kVA² − kW²)Reference
Use the engineer of record's number when you have it. When you do not, these ranges are where most projects land.
| Application | Typical PF | Note |
|---|---|---|
| AI / HPC data center | 0.85 – 0.95 | GPU power supplies are good; cooling and UPS losses pull the site number down |
| Traditional data center | 0.90 – 0.95 | Modern PFC-corrected server supplies |
| Bitcoin mining | 0.95 – 0.99 | Near-unity at the miner; check the transformer for harmonics |
| Industrial, motor heavy | 0.70 – 0.90 | Uncorrected induction motors; capacitor banks bring it up |
| Commercial office | 0.85 – 0.95 | Mixed lighting, HVAC, IT |
| Hospital | 0.80 – 0.90 | Imaging equipment and chillers |
| Resistive heating | 1.00 | Heat trace, resistance furnaces |
A lower power factor means more kVA for the same kW. At 0.8, a 1000 kW load needs a 1250 kVA transformer before headroom.
After the number
The rating is one line. The rest of the spec is what we need to price it in under 30 minutes.
Primary and secondary, with the winding connection. 12470 delta to 480Y/277 is the most common padmount we quote.
Size the transformer, then add 25%. It costs less than the second transformer you buy when the load grows.
GPU halls and drive-heavy plants push current distortion. Ask for a K-4 or K-13 rating, or a derate, in the spec.
ONAN or ONAN/ONAF. Padmount, substation, or dry-type indoors. This sets the footprint and the price.
FAQ
Short answers. If yours is not here, the quote desk picks up.
Because the transformer carries the full current, and current follows kVA, not kW. A 1000 kW load at 0.8 PF pulls the same amps as a 1250 kW load at unity. Undersize in kW and the windings run hot.
Yes. Most data center and commercial designs assume 0.9 to 0.95 at the service. Enter that and move on; the quote confirms the size.
No. kVA = kW ÷ PF regardless of phase. Phase only changes which list of standard sizes the calculator picks from.
25% is the floor for a new build. A campus with a known phase two gets 35 to 50%. Over 50% and you are paying for iron that never sees load, and a lightly loaded transformer has worse efficiency, not better.
The math is the same; use the absolute value. Leading power factor shows up on sites with big capacitor banks or lightly loaded UPS systems, and it can raise the voltage. Mention it and we will flag it on the spec.