UPS sizing calculator
List the equipment you want to keep running. The calculator totals the load, allows headroom, converts watts to VA with the power factor and rounds up to a common UPS size.
UPS rating
2,000 VA
Recommended UPS rating, rounded up to a common size
- Total load
- 1,220 W
- With 25% headroom
- 1,525 W
- Exact requirement
- 1,906 VA
- Real power of that size
- 1,600 W
- Load on that size
- 76%
This load is above the largest common single-phase size here. A larger online UPS or a split load may suit. Send us the details.
Planning estimate. Backup time depends on the model and the batteries fitted, so it is matched to a model and not calculated here.
Choosing the type of UPS
Shutting down safely
A line-interactive UPS at the recommended rating normally gives enough time to save work and shut equipment down. Choose online if the mains is unstable or the load is sensitive.
| Feature | Line-interactive | Online | Online with external batteries |
|---|---|---|---|
| Best for | Desktop PCs, routers, PoE switches and small recorders where the mains is mostly stable. | Servers, recorders and equipment on poor or noisy mains, and sensitive loads. | Sites that need hours of backup, such as recorders that must run through long outages. |
| Power conditioning | Corrects voltage with automatic voltage regulation and passes mains through while it is within range. | Rebuilds the output continuously, so equipment is isolated from mains disturbances. | As online. |
| Switch to battery | A few milliseconds. | None. | None. |
| Backup time | Minutes, from the internal battery. | Minutes, from the internal battery. | Hours, set by the size of the external battery bank. |
| Points to weigh | Lower cost and quiet running. | Higher cost, fan noise and more heat. | The battery bank needs space and ventilation. Recharge time grows with the bank size. |
How the rating is worked out
The rating is a planning figure. It tells you the VA size to look for, and the datasheet of the model you choose has the final word on watts and backup time.
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Total load
sum of (quantity x watts) for every row
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Required watts
total load x (1 + headroom)
Headroom allows for growth and keeps the UPS away from its limit.
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Required VA
required watts / power factor
Power factor links real power in watts to apparent power in VA. The default 0.8 is a planning value for line-interactive units. Many online units are rated at 0.9 or 1.0, and the watt rating on the datasheet is the limit that counts.
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UPS rating
next common size at or above the required VA
Common sizes: 600, 1,000, 1,500, 2,000, 3,000, 5,000, 6,000, 10,000 VA.
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Load on that size
total load / (rating x power factor)
| Rating | Watts at power factor 0.8 |
|---|---|
| 600 VA | 480 W |
| 1,000 VA | 800 W |
| 1,500 VA | 1,200 W |
| 2,000 VA | 1,600 W |
| 3,000 VA | 2,400 W |
| 5,000 VA | 4,000 W |
| 6,000 VA | 4,800 W |
| 10,000 VA | 8,000 W |
What the rating cannot know
- Backup time is specific to each model and its batteries. The calculator does not estimate it. Check the runtime chart on the datasheet at your load.
- Laser printers, motors and compressors draw a large surge at start-up. Size for the peak, or keep them off the UPS.
- The watt rating is the limit that counts, not the VA figure alone. Keep the load within it.
UPS systems and batteries
Ask for a quotation
Press Ask for a quotation in the results panel and your load list and rating are added to the requirement field. Add your contact details and send. Our sales desk will reply with matching UPS models and batteries, subject to stock.
To talk it through, call +91 94350 11393.