How long will my battery backup power my equipment? How much autonomy should I expect?

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There is a free calculator at:

You can use the online calculator or follow the guide above: To figure out how long a battery backup system will keep your equipment powered there is a simple calculation you can do ((Battery Capacity (Ah) x Battery Voltage (12V)) x Percent Discharge (50%)) / Your Equipment Load (Watts)

So, let’s say you’re 12V battery capacity is 100Ah and your equipment load is 50W. We use 50% discharge because you really don’t want to discharge batteries much more than 50% if you want them to have a long life 100Ah x 12V = 1200Wh. 1200Wh * 0.5 (50% discharge) = 600Wh (adjusted battery capacity) 600Wh / 50W = 12hrs backup time. As you can see in the above example, with 100Ah of battery and 50W load and no sun, the batteries will provide at least 12hrs run time. Be sure to size the batteries for your worst-case scenario.