Convert amp-hours to watt-hours
A rough energy estimate is battery amp-hours × nominal voltage. A 100 Ah 12 V battery is about 1,200 Wh nominal before applying depth-of-discharge limits, inverter losses and real battery behavior.
Usable energy is less than nameplate energy
Different battery chemistries and battery-management systems have different recommended usable ranges. TowAtlas therefore includes a depth-of-discharge input rather than assuming the full nameplate capacity is available.
Inverter efficiency matters
Running 120 V appliances from a battery through an inverter introduces losses. The calculator applies an efficiency factor to reduce the usable AC-side energy estimate.
Runtime is not perfectly linear
High loads, battery age, temperature, wiring losses and voltage cutoffs can reduce runtime. Treat the result as a planning estimate and leave reserve for critical loads.
Separate continuous and intermittent loads
A refrigerator compressor, water pump or furnace blower may cycle rather than run continuously. For better planning, estimate average watts over time instead of adding every appliance’s maximum rating as if it runs constantly.
Solar changes the daily energy budget
Solar can replace energy during daylight, so a pure battery runtime calculation is conservative for a system receiving meaningful charge. For multi-day planning, compare daily energy consumption with expected daily charging rather than only calculating hours to empty.
Common questions
How do I convert 100 Ah to watt-hours?
Multiply amp-hours by nominal voltage. At 12 V, 100 Ah is about 1,200 Wh nominal before usable-depth and efficiency adjustments.
Can I run an air conditioner from batteries?
Possibly with a suitably designed battery and inverter system, but air conditioners are large loads. Use actual running and startup specifications and verify the system with the equipment manufacturers.
Open the related TowAtlas calculator and use your saved Garage setup when available.