UPS Runtime Calculator
Pick your UPS capacity, put in what it actually carries - a router and laptop pull around 80 watts, a desktop with monitors closer to 200 - and set the battery age. The estimate gives minutes of runtime, the power ceiling in watts, and how hard you are loading the unit.
Vendor pages quote half-load runtime on a new battery in lab conditions. This one uses the field model - consumer units carry roughly 0.15 Wh of battery per VA, about 85% deliverable, aging fast after year two - and says plainly that the goal for most setups is 5 to 10 clean minutes to save work and shut down, not to keep computing through the outage.
How to use
- Pick the VA rating printed on the UPS; the watt ceiling is about 60% of it.
- Enter the real load - add up the devices plugged in, not what you wish you had.
- Set battery age honestly; over three years expect a third gone even with no use.
Frequently asked questions
How long will a 1000VA UPS run a router and laptop?
At about 80 watts combined, expect roughly 90 minutes from a healthy battery. The same unit at a 500 W desktop load drops to about 13 minutes - load, not the VA badge, sets the clock.
Why does my UPS die in minutes when the box said longer?
The box quotes half-load runtime on a new battery. Batteries lose 20-30% of capacity by year three even unused, and loads creep up as devices accumulate - both shave the same curve.
Should I buy a UPS sized for hours of runtime?
No - past 10-15 minutes each extra hour buys expensive battery banks and lithium conversions. The standard play is a short-run UPS on anything with unsaved work, and a generator or power station for duration.
Do UPS batteries need replacing?
Every 3-5 years regardless of use - they age on the shelf. If the self-test beeps or runtime visibly halves, swap in the same spec; a fresh battery makes an old UPS genuinely new again.