Key numbers
- kWh = Ah × V ÷ 1,000; Ah = kWh × 1,000 ÷ V
- 100 Ah at 12.8 V = 1.28 kWh
- A 12 V LiFePO4 battery is nominally 12.8 V; a 12 V lead-acid battery is 12 V
- Series adds volts, parallel adds amp-hours; total kWh is the same
On this page
How to use the Amp Hours to kWh
- 1Enter your numbersFill in capacity (Ah), battery voltage (V) and number of batteries. Every field starts with a typical value you can overwrite.
- 2Check the assumptionskWh = Ah × V ÷ 1,000. A 12 V LiFePO4 battery is nominally 12.8 V; a 12 V lead-acid is 12 V. Wiring in series adds voltage; in parallel adds amp-hours — energy is the same either way.
- 3Read the resultsThe calculator shows stored energy, watt-hours, usable at 90% (lithium), usable at 50% (lead-acid) and runs a 100 w load for (lithium), and updates as you type.
- 4Use the resultCompare it with your bill, a quote or a product spec sheet before you buy or install anything.
Results update as you type. Back to the calculator ↑
This amp hours to kWh converter turns a battery’s Ah rating into the energy it stores in kilowatt-hours and watt-hours. That figure lets you compare batteries of different voltages and size a solar or backup system. It also shows usable energy for lithium and lead-acid chemistries and how long the battery runs a 100 W load.
How to convert amp hours to kWh
An amp-hour (Ah) is a measure of charge: one amp flowing for one hour, or 3,600 coulombs (NIST SP 811). Energy depends on voltage too:
- Wh = Ah × V
- kWh = Ah × V ÷ 1,000
- Ah = kWh × 1,000 ÷ V
- Usable kWh = kWh × depth of discharge (about 90% for LiFePO4, 50% for lead-acid; see Battery University)
With more than one battery, multiply the Ah by the number of batteries at a single battery’s voltage. Series or parallel wiring does not change the total energy.
Worked example with the default values
- Capacity 100 Ah, voltage 12.8 V (a 12 V LiFePO4 battery), 1 battery
- Stored energy: 100 × 12.8 ÷ 1,000 = 1.28 kWh (1,280 Wh)
- Usable at 90% (lithium): 1.28 × 0.9 = 1.152 kWh
- Usable at 50% (lead-acid): 1.28 × 0.5 = 0.64 kWh
- Runtime on a 100 W load (lithium): 1,152 ÷ 100 = 11.5 hours
Ah to kWh conversion table
| Capacity | 12 V | 12.8 V (LiFePO4) | 24 V | 48 V | 51.2 V (LiFePO4) |
|---|---|---|---|---|---|
| 50 Ah | 0.6 kWh | 0.64 kWh | 1.2 kWh | 2.4 kWh | 2.56 kWh |
| 100 Ah | 1.2 kWh | 1.28 kWh | 2.4 kWh | 4.8 kWh | 5.12 kWh |
| 200 Ah | 2.4 kWh | 2.56 kWh | 4.8 kWh | 9.6 kWh | 10.24 kWh |
| 280 Ah | 3.36 kWh | 3.58 kWh | 6.72 kWh | 13.44 kWh | 14.34 kWh |
| 300 Ah | 3.6 kWh | 3.84 kWh | 7.2 kWh | 14.4 kWh | 15.36 kWh |
| 314 Ah | 3.77 kWh | 4.02 kWh | 7.54 kWh | 15.07 kWh | 16.08 kWh |
| 400 Ah | 4.8 kWh | 5.12 kWh | 9.6 kWh | 19.2 kWh | 20.48 kWh |
kWh to Ah conversion table
| Energy | at 12 V | at 24 V | at 48 V | at 51.2 V |
|---|---|---|---|---|
| 1 kWh | 83 Ah | 42 Ah | 21 Ah | 20 Ah |
| 2.5 kWh | 208 Ah | 104 Ah | 52 Ah | 49 Ah |
| 5 kWh | 417 Ah | 208 Ah | 104 Ah | 98 Ah |
| 5.12 kWh | 427 Ah | 213 Ah | 107 Ah | 100 Ah |
| 10 kWh | 833 Ah | 417 Ah | 208 Ah | 195 Ah |
| 10.24 kWh | 853 Ah | 427 Ah | 213 Ah | 200 Ah |
Amp hours vs watt hours
Amp-hours measure charge and watt-hours measure energy (Wh = Ah × V); for Wh results and the reverse Wh to Ah conversion, use the amp hours to watt hours converter.
What affects usable energy
- Chemistry. LiFePO4 batteries tolerate deep discharge (BU-205); lead-acid and AGM batteries last far longer if you use only about half their rating.
- Discharge rate. Lead-acid Ah ratings are measured at a slow rate, often 20 hours. Fast discharges deliver less (the Peukert effect).
- Inverter losses. Running AC loads through an inverter loses some energy. The battery runtime calculator includes inverter efficiency.
- Temperature and age. Cold and older batteries hold less.
- Voltage choice. For large systems, 24 V or 48 V banks carry lower current for the same power, which means thinner cables and smaller losses.
Pro tip
History: Peukert’s law
Why a lead-acid battery’s Ah rating depends on how fast you draw it was described in 1897 by the German scientist Wilhelm Peukert, who showed that the capacity of lead-acid cells falls as the discharge current rises (Peukert’s law). That is why lead-acid ratings quote a slow rate, often 20 hours, and why this calculator’s usable-energy figures are best treated as estimates for heavy loads. Lithium iron phosphate cells are much less affected.
References
- Thompson, A. & Taylor, B. N. (2008). Guide for the Use of the International System of Units (SI). NIST Special Publication 811. doi:10.6028/NIST.SP.811e2008
- Battery University. BU-501: Basics about Discharging. batteryuniversity.com
Sizing a battery bank
Battery banks store energy from solar panels and wind turbines so clean, renewable energy is available at night or during an outage. To size a complete system from your daily kWh and days of autonomy, use the off-grid solar calculator. Our off-grid solar system guide explains how batteries, inverters and charge controllers work together. If kWh is new to you, start with what is a kilowatt-hour.
Common mistakes when converting Ah to kWh
- Comparing Ah across voltages. A 100 Ah, 48 V battery holds four times the energy of a 100 Ah, 12 V battery. Compare kWh, not Ah.
- Adding Ah in series. Two 100 Ah batteries in series are still 100 Ah, at double the voltage. Enter one battery’s Ah and the number of batteries, and set the voltage to one battery’s voltage.
- Using charging voltage. A 12 V lead-acid battery may read 14 V or more while charging. Use the nominal voltage (12 V or 12.8 V) for energy.
- Treating rated kWh as usable. Subtract the depth-of-discharge margin before sizing loads.
FAQ
Frequently asked questions
How do I convert Ah to kWh?
Multiply amp-hours by the nominal battery voltage and divide by 1,000. A 200 Ah, 12 volt battery holds 200 × 12 ÷ 1,000 = 2.4 kWh. A 100 Ah, 48 volt battery holds 4.8 kWh. Without the voltage, Ah cannot be converted to energy.
How do I convert kWh to Ah?
Multiply kWh by 1,000 and divide by the voltage. A 5 kWh battery bank at 48 volts is about 104 Ah; at 12 volts it would be about 417 Ah. Higher-voltage banks need fewer amp-hours and carry lower current for the same energy.
How many kWh is a 100Ah battery?
At 12 volts nominal, a 100 Ah lead-acid battery stores 1.2 kWh, of which about 0.6 kWh is usable at 50% depth of discharge. A 100 Ah, 12.8 volt lithium iron phosphate battery stores 1.28 kWh, with about 1.15 kWh usable at 90%.
Why is a 12V lithium battery 12.8V?
Lithium iron phosphate cells have a nominal voltage of about 3.2 volts, and four in series make 12.8 volts. They are sold as 12 volt batteries because they replace 12 volt lead-acid batteries. Use 12.8 for energy calculations.
Does wiring batteries in series or parallel change kWh?
No. Two 12 volt 100 Ah batteries in series make 24 volts and 100 Ah; in parallel they make 12 volts and 200 Ah. Both store 2.4 kWh. The calculator multiplies one battery's Ah by the number of batteries at the voltage you enter.
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Last updated October 25, 2026. Part of our renewable energy toolkit. Found an error? Tell us.