Runtime calculator
Pick your loads, pick a battery, and see the hours. The calculator applies the 85 percent usable factor this site uses everywhere, counts each load at its average watts (running watts times duty cycle), and checks the biggest motor surge against an output figure you can enter. Nothing is saved or sent anywhere; the math happens in your browser and the inputs stay visible, because a calculator that hides its assumptions is just an opinion.
Your loads
Pick at least one load to see runtimes.
How to read the result
Runtime alone is the honest best case for one load. Combined runtime is what an outage actually feels like, because loads share one battery. The surge check exists because the most common failure in this category is not an empty battery; it is a station tripping on a pump start at 2 a.m. The default watts and duty cycles are planning figures for typical appliances, and every one of them is editable, because your fridge is not our fridge. The full method, with worked examples, is in runtime, explained and calculated.