Quick power factors:
Which power factor to use
| Equipment | Typical PF | Notes |
|---|---|---|
| Budget standby / line-interactive UPS output rating | 0.60 | e.g. 1500 VA / 900 W |
| Consumer pure sine UPS output rating | 0.60 to 0.70 | e.g. 1500 VA / 1000 W |
| Recent business and online UPS output rating | 0.90 to 1.0 | Check the spec sheet |
| Computer or server PSU with active PFC | 0.95 to 0.99 | At moderate to high load |
| Small adapters without PFC | 0.45 to 0.70 | Phone chargers, older bricks |
| Induction motors (running) | 0.60 to 0.85 | Plus a large startup surge |
| Heaters, incandescent lamps | 1.00 | Resistive, but very high wattage |
Two power factors, two jobs
The UPS power factor converts the box's VA rating to its watt capacity. The load power factor converts your devices' watts to the VA they demand. Mixing the two is the classic error: multiplying your devices' watts by 0.6 to "get VA" overstates the VA demand of modern electronics by more than 50%.
For the full explanation, see VA vs watts. To size a UPS from these numbers, use the UPS sizing calculator.
Frequently asked questions
How do I convert VA to watts?
Multiply VA by the power factor. For a UPS, use its rated output power factor, which is its watt rating divided by its VA rating (often 0.6 for budget units and 0.9 to 1.0 for business and online units). For modern electronics, the power factor is about 0.95 to 0.99.
How many watts is 1000 VA?
At a power factor of 0.6, 1000 VA is 600 W, which is the typical rating of budget 1000 VA UPS units. At 0.9 it is 900 W. The UPS spec sheet states the exact watt figure; use it rather than converting.
How many amps does a 1500 VA UPS draw?
At full output, 1500 VA at 120 V is 12.5 A at the output. Input current is higher while the battery recharges and because of conversion losses, which is why many 1500 VA units still use a standard 15 A plug and larger units move to 20 A plugs.
Is kVA the same as kW?
Only when the power factor is 1.0. kVA is apparent power and kW is real power. Data center UPS systems are increasingly rated at unity power factor, where the two numbers match.