Amp Hours to kWh Conversion (Ah to Wh Calculator and Chart)

To convert amp-hours to kilowatt-hours, you must multiply amp-hours by the battery voltage. Then divide by 1,000. For example, a 12 V 100 Ah battery holds 1.2 kWh. You calculate this as 12 × 100 ÷ 1,000. Also, a 48 V 100 Ah battery holds 4.8 kWh.

The formulas

• Wh = Ah × V
• kWh = Ah × V ÷ 1,000
• Ah = kWh × 1,000 ÷ V

Amp-hours alone do not tell you how much energy a battery stores. A 100 Ah battery at 48 V stores four times as much as a 100 Ah battery at 12 V. That is why solar professionals compare batteries in kWh.

Nominal voltage for lithium batteries

LiFePO4 cells have a nominal voltage of 3.2 V, so:

• a “12 V” lithium battery (4 cells) is 12.8 V nominal
• a “24 V” lithium battery (8 cells) is 25.6 V
• a “48 V” lithium battery is either 51.2 V (16 cells, most common) or 48 V (15 cells)

So, a 12 V 100 Ah lithium battery stores 1.28 kWh. A 51.2 V 100 Ah rack battery, however, stores 5.12 kWh.

Conversion chart

Capacity	12 V (lead-acid)	12.8 V (LiFePO4)	24 V	48 V	51.2 V
50 Ah	0.60 kWh	0.64 kWh	1.2 kWh	2.4 kWh	2.56 kWh
100 Ah	1.20 kWh	1.28 kWh	2.4 kWh	4.8 kWh	5.12 kWh
200 Ah	2.40 kWh	2.56 kWh	4.8 kWh	9.6 kWh	10.24 kWh
280 Ah	3.36 kWh	3.58 kWh	6.7 kWh	13.4 kWh	14.3 kWh
400 Ah	4.80 kWh	5.12 kWh	9.6 kWh	19.2 kWh	20.5 kWh

Converting kWh needs into amp-hours

If you calculated that your cabin needs 6 kWh of storage:

• at 12 V: 6,000 ÷ 12 = 500 Ah
• at 24 V: 6,000 ÷ 24 = 250 Ah
• at 48 V: 6,000 ÷ 48 = 125 Ah

Remember that this is total capacity. The usable portion depends on chemistry. So, you divide your daily need by 0.85 for LiFePO4. You divide by 0.50 for lead-acid first. Our guide to how many batteries you need for solar explains this.

Series and parallel change Ah and V differently

• Series wiring adds voltage. Ah, however, stays the same. For instance, two 12 V 100 Ah batteries in series make 24 V 100 Ah (2.4 kWh).
• Parallel wiring adds Ah. Voltage, however, stays the same. For example, two 12 V 100 Ah batteries in parallel make 12 V 200 Ah (2.4 kWh).

Either way the total energy is identical. See how to wire batteries in series and parallel.

Power banks: mAh to Wh

Power banks and phone batteries list capacity in milliamp-hours at the internal cell voltage, usually 3.6 or 3.7 V:

Wh = mAh × V ÷ 1,000

A 20,000 mAh power bank at 3.7 V holds 74 Wh. After conversion losses to 5 V USB, expect about 50 to 55 Wh. This will reach your phone. As a result, this is around four phone charges. Airlines usually limit carry-on power banks to 100 Wh. You need approval for more.

Watts vs watt-hours

• Watts (W) measure power: how fast energy is used right now.
• Watt-hours (Wh) measure energy: power multiplied by time.

A 100 W TV running for 3 hours uses 300 Wh. Batteries are sized in Wh or kWh; inverters are sized in W. Mixing these up is the most common sizing mistake.

Worked examples: real products converted

Product (as advertised)	Calculation	Energy
12 V 100 Ah LiFePO4 battery	12.8 × 100 ÷ 1,000	1.28 kWh
12 V 230 Ah AGM battery	12 × 230 ÷ 1,000	2.76 kWh (about 1.4 kWh usable at 50%)
48 V 100 Ah rack battery (51.2 V)	51.2 × 100 ÷ 1,000	5.12 kWh
6 V 225 Ah golf-cart battery	6 × 225 ÷ 1,000	1.35 kWh each
20,000 mAh power bank (3.7 V)	3.7 × 20 ÷ 1,000	0.074 kWh (74 Wh)
1,024 Wh power station	already in Wh	1.02 kWh

You usually wire golf-cart batteries in series pairs. This is for off-grid banks. For example, two 6 V batteries equal 12 V and 225 Ah. As a result, this is 2.7 kWh.

Usable kWh vs rated kWh

Rated kWh is the total capacity. Usable kWh depends on chemistry. It also depends on your chosen depth of discharge.

Battery	Rated	Usable (planning)
12 V 100 Ah LiFePO4	1.28 kWh	about 1.09 kWh (85%)
12 V 100 Ah AGM	1.2 kWh	about 0.6 kWh (50%)
48 V 200 Ah LiFePO4	10.24 kWh	about 8.7 kWh

Then, for AC loads, multiply by inverter efficiency (about 0.90) to find what reaches your appliances.

Converting appliance amps to watts

Appliances often list current instead of power:

• AC appliances: Watts ≈ Volts × Amps. For example, 120 V × 1.5 A = 180 W. Also, 230 V × 0.8 A = 184 W. Motors and electronics have a power factor below 1. So, real watts are often a bit lower.
• DC appliances: Watts = Volts × Amps exactly (for example 12 V × 4 A = 48 W).

Watt-hours per day equals watts multiplied by hours of use. Add everything. Then, compare this with your battery’s usable kWh. See off-grid load calculation.

Common mistakes

• Comparing batteries by Ah across different voltages.
• Assuming a 12 V lithium battery is exactly 12 V; it is 12.8 V nominal. So, it has slightly more energy than a 12 V lead-acid battery with the same Ah.
• Forgetting depth of discharge when calculating runtime.
• Treating power bank mAh as 5 V figures; they are rated at the internal cell voltage (3.6 to 3.7 V).

FAQ

How many kWh is a 200 Ah lithium battery?

At 12.8 V, 200 Ah is 2.56 kWh. At 51.2 V it is 10.24 kWh.

How many amp-hours is 10 kWh?

At 48 V, 10 kWh is about 208 Ah. At 12 V it is about 833 Ah.

How long will 1 kWh last?

It runs a 100 W load for about 10 hours. It can also run a 1,000 W load for about 1 hour, minus inverter losses. Try your loads in the calculator.

How many amp-hours is a 5 kWh battery?

At 12.8 V about 390 Ah; at 25.6 V about 195 Ah; at 51.2 V about 98 Ah.

How do I convert kWh to amp-hours for a 24 V system?

Ah = kWh × 1,000 ÷ 24 (or ÷ 25.6 for LiFePO4). For example, 6 kWh ÷ 24 V = 250 Ah.

Related guides

• How Long Will a 100Ah Battery Last? (Runtime Calculator + Table)
• Battery Voltage Chart for 12V, 24V and 48V (LiFePO4 and Lead-Acid)
• Can You Mix Old and New Batteries in a Solar Bank?
• LiFePO4 vs AGM Batteries for Solar: Which Is Better?

Sources and further reading

• Battery University: BU-402 What Is C-rate?: This covers charge and discharge rate. It also covers capacity and runtime.
• Battery University: BU-205 Types of Lithium-ion: how lithium chemistries, including LiFePO4, compare.