How to estimate real run time for devices on a compact system?

Estimating run time: a practical approach for small solar setups

To estimate how long a device will run, calculate energy consumption and compare it to usable battery capacity. Start with device wattage and operating hours.

Steps to estimate:

• Multiply device wattage by expected hours of use to get watt-hours
• Use battery usable capacity (total Wh times depth-of-discharge percentage) for available energy
• Subtract estimated system losses (10–20%) for inversion and wiring

For example, a 20 W speaker running 5 hours uses 100 Wh. A 500 Wh battery with 80% usable capacity provides about 400 Wh, so it could run that speaker for roughly 20 hours, minus losses. Doing this for each device helps size batteries and panels for real-world expectations.