Need any idea how long your UPS will last for? Eg How much runtime will you get out of your UPS? Then this UPS Runtime Calculator is just what you need.
You’ll need to know how much power (in Watts) your UPS is delivering. Then you’ll need to know how many battery blocks and of what Ampere Hour capacity are in your UPS.
This calculator is based upon 12V blocks only and will only accept integer values. So, if you have one single 6V battery of 12Ah capacity, then you’ll need to say it’s a 12V 6Ah battery. If the spec of your battery is not in Ampere Hours but Watt Hours, then as a very rough guide divide the Wh rating by 4 to get the Ah. If you have 7.2Ah or 8.5Ah then if you round down this will give you a minimum, and round up will give you a maximum.
Note, the calculator is approximate. There are assumptions made on standby current consumption and inverter efficiency that will be different for different UPS and also different at different load levels. Please just use as a guide.
If your load varies over time, you’ll need to estimate the average power consumption. You’ll need to size a UPS to meet the maximum power draw expected, but calculate the runtime based upon the average power consumption.
If you want to select a UPS to meet load and runtime calculators please use the UPS Selection Tool.
If you’ve used the UPS Runtime Calculator please leave a comment or drop us a line with any ideas.
6 thoughts on "UPS Runtime Calculator"
Good evening, I am writing on behalf of the Leighton Buzzard Narrow Gauge Railway in Bedfordshire. As part of our improved Christmas experience we are looking to create a “train of light” with LED Rope lights running the length of our train. We have found the ideal product that can be cut to length etc, but has 240v ac as power supply. Although our initial plan was to use a small generator mounted in a brake van at the end of the train, the Health & Safety group are having a field day of opposition. It has been suggested that we might be able to make it work with an invertor running off a 24v lorry battery.
The power required for total 60metres of rope would be just under 250watts, and it would need to run for 4 hours. It could be split into two supplies (one each side if easier)
Is this something you could advise us on?
I live in Bicester so could drop in if you can help.
Leighton Buzzard Railway
Hi Colin. If you play about with the numbers you can see that you’ll need 140Ah of battery capacity at 12V to get 4 hours runtime for a 250W load.
If you like, I have a very old ex demo 300W sine wave inverter your club is welcome to. I’d attach two 12V 100Ah batteries in parallel to this and that will run the lights for over 6 hours. Higher capacity give you the benefit of increasing battery life by not discharging to end of discharge points (you get more cyclic life this way). You will need, however to have a separate system to recharge the batteries. If you give us a call or ping us an email and let us know when you can pop by I’ll make sure it is available for you to collect.
Best ups calculator when you just need a tool to quickly estimate the runtime. You don’t need to fill out a wall of forms like on other sites. Thank you very much.
Hello, I am interested in buying this UPS for my computer and montior. My computer is about 500 watts and my monitor is 50 watts. How long do you think this UPS would last on with this power draw? Thanks
Well, the problem here is the UPS is rated at only 260W, so if your total load is 550W then this UPS isn’t powerful enough and will overload. Note though that the computer power supply rating is not an indicator of how much power the computer actually takes, but rather how much power the PSU can deliver. The UPS itself contains a 12V 2.9Ah battery. This is quite tiny and I wouldn’t expect the UPS to provide more than 1 – 2minutes at its full load rating.