Enter both values to calculate watt hours
Amp Hours (Ah)
Volts (V)
Common:
Watt Hours (Wh)
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Understanding Battery Capacity
The relationship between amp hours and watt hours follows the Energy Formula:
- Energy (Wh) = Capacity (Ah) × Voltage (V)
- Capacity (Ah) = Energy (Wh) ÷ Voltage (V)
For Solar Battery Systems
Understanding these relationships helps you:
- Compare batteries - Wh lets you compare batteries of different voltages
- Size your system - Calculate how long your loads can run
- Plan upgrades - Understand capacity when changing voltage
- Match components - Ensure charge controller and inverter compatibility
Real-World Solar Examples
12V 100Ah LFP Battery
A 12V 100Ah lithium iron phosphate battery stores 1,200Wh (1.2 kWh). With 90% usable depth of discharge, you get about 1,080Wh — enough to run a 60W refrigerator for 18 hours.
48V 100Ah Battery Bank
A 48V 100Ah lithium battery bank stores 4,800Wh (4.8 kWh) — approximately one-third of a Tesla Powerwall's 13.5 kWh capacity.
Same Energy, Different Voltage
A 24V 200Ah battery bank stores 4,800Wh — the same energy as a 48V 100Ah bank. Voltage and amp hours trade off against each other, which is why Wh is the true measure of stored energy.
When You'll Need This Conversion
- Sizing a Battery Bank for Overnight Loads — Two 12V 100Ah batteries provide 2,400Wh total. With 90% usable DoD on LFP, that is 2,160Wh usable — just enough for 2,000Wh of overnight loads, but with little margin.
- Comparing Batteries from Different Vendors — A "12V 100Ah" and a "24V 50Ah" battery sound different but store identical energy: 1,200Wh. Without converting to Wh, buyers frequently overpay for batteries that appear larger based on Ah alone.
- Calculating Solar Panels for Recharge — A 48V 100Ah battery bank (4,800Wh) needs recharging from 20% to 100% (3,840Wh). With 400W panels in 5 peak sun hours, each panel produces 2,000Wh/day. Two panels cover the recharge.
Solar Tips & Common Mistakes
Ah Without Voltage Is Meaningless: A 12V 200Ah battery (2,400Wh) stores less energy than a 48V 100Ah battery (4,800Wh), even though 200Ah sounds "bigger." Always convert to Wh before comparing batteries at different voltages.
Account for Inverter Efficiency: When converting battery Ah to usable AC watt-hours, multiply by inverter efficiency (typically 90–93%). A 12V 100Ah battery provides 1,200Wh DC but only about 1,080–1,116Wh AC.
Nominal vs Actual Voltage: A "12V" LFP battery actually operates between 10.0V and 14.6V, with nominal voltage around 12.8V. Using 12.8V instead of 12V: 100Ah × 12.8V = 1,280Wh — a 6.7% difference that compounds across large banks.
Solar Calculators
Related Conversion Calculators
Last updated: January 5, 2026
