How do you convert watt-hours to amp-hours?

Divide watt-hours by the battery voltage. The formula is Ah = Wh / V. For example, a 2,400 Wh battery at 12V has a capacity of 200 Ah (2,400 / 12). The same 2,400 Wh at 48V equals only 50 Ah (2,400 / 48). You must know the system voltage to perform this conversion.

How many amp-hours is a Tesla Powerwall?

The Tesla Powerwall 3 stores 13,500 Wh (13.5 kWh) at a nominal 48V. Converting to amp-hours: 13,500 / 48 = 281 Ah. The Powerwall 2 stored 13,500 Wh at approximately 50V nominal, giving about 270 Ah.

Why would I need to convert Wh to Ah?

You need amp-hours to size charge controllers, select fuses and breakers, choose the correct wire gauge, and match batteries in a bank. Charge controllers are rated in amps (e.g., 30A, 60A MPPT), fuses are rated in amps, and wire gauge is selected based on current draw. Energy (Wh or kWh) tells you capacity, but current (amps) determines your hardware.

Does converting Wh to Ah at a higher voltage give fewer amp-hours?

Yes. Higher voltage means fewer amps for the same energy. This is precisely why 48V systems are preferred for larger installations -- lower current means thinner (cheaper) wires, smaller fuses, and less voltage drop over long cable runs. A 4,800 Wh system at 12V draws 400A; at 48V it draws only 100A.

How do I convert kWh to Ah?

First multiply kWh by 1,000 to get Wh, then divide by voltage. Ah = (kWh x 1,000) / V. For example, 5 kWh at 48V: (5 x 1,000) / 48 = 104 Ah.

What voltage should I use in the formula -- nominal or actual?

Use the nominal voltage. A '12V' battery actually operates between 10.5V (empty) and 14.4V (charging), but its nominal voltage is 12V. A '48V' LiFePO4 battery operates between 40V and 54.4V, with a nominal of 48V (or 51.2V for some manufacturers). Nominal voltage is what the manufacturer uses for the Ah rating.

How do series and parallel wiring affect Ah and Wh?

Series wiring increases voltage while keeping Ah the same. Two 12V 100Ah batteries in series give 24V 100Ah (2,400 Wh). Parallel wiring increases Ah while keeping voltage the same. Two 12V 100Ah batteries in parallel give 12V 200Ah (2,400 Wh). Both configurations store the same total energy -- they just deliver it at different voltage and current combinations.

Watt-Hours To Amp-Hours Calculator (Wh To Ah Conversion)

Amp-hours = Watt-hours / Volts. You need this conversion whenever you are sizing charge controllers, selecting fuses, choosing wire gauge, or matching batteries in a bank. A 13,500 Wh Tesla Powerwall at 48V is 281 Ah. A 2,400 Wh lead-acid bank at 12V is 200 Ah. This guide covers the formula, a reference table of common conversions, and the practical reasons why converting from energy (Wh) to current capacity (Ah) matters for system design.

Calculator

Battery voltage

Battery capacity

Battery chemistry

Target charge time

hrs

Required solar panel size

To charge a 100Ah 12V Lithium (LiFePO4) battery in 5 hours

Energy to charge

1.26kWh

If you use 100W panels

panels needed

If you use 200W panels

panels needed

171 kg

CO₂ avoided per year

0.04

equivalent US homes powered

trees planted equivalent

$74

estimated annual savings

Chemistry	Efficiency	Cycle Life	Panel Watts
Lithium (LiFePO4)	95%	3,000–5,000	252 W
Deep Cycle AGM	85%	500–1,000	283 W
Lead-Acid Flooded	80%	300–500	300 W

Tap to see sensitivity analysisSensitivity analysis

Sensitivity range
Scenario	Value
Low (-20%)	202 W
Expected	252 W
High (+20%)	302 W

Battery chemistry has the biggest effect \u2014 switching from lead-acid to lithium reduces required panel watts by ~20%.

What size battery do I need?See production for your state

The Formula: Ah = Wh / V

The conversion from watt-hours to amp-hours is the inverse of the more commonly seen Wh = Ah x V.

Ah = Wh / V

Where:

Ah = amp-hours (charge capacity)
Wh = watt-hours (energy capacity)
V = nominal battery voltage

This works because power equals voltage times current (W = V x A). Rearranging for current gives A = W / V. Extend both sides over time and you get Ah = Wh / V.

When You Need This Conversion

Battery manufacturers and home energy systems increasingly list capacity in watt-hours or kilowatt-hours (the Tesla Powerwall is "13.5 kWh," the Enphase IQ Battery 5P is "5 kWh"). But many of the components you need to connect them are rated in amps:

Charge controllers: rated in amps (30A, 40A, 60A, 100A MPPT)
Fuses and breakers: rated in amps
Wire gauge: selected based on maximum current draw
Battery disconnect switches: rated in amps
Inverter DC input: specified in amps at a given voltage

To select these components correctly, you need to convert from energy to current -- from Wh to Ah.

Common Wh To Ah Conversions

Energy (Wh)	At 12V	At 24V	At 48V
600 Wh	50 Ah	25 Ah	12.5 Ah
1,200 Wh	100 Ah	50 Ah	25 Ah
2,400 Wh	200 Ah	100 Ah	50 Ah
4,800 Wh	400 Ah	200 Ah	100 Ah
5,120 Wh	427 Ah	213 Ah	107 Ah
9,600 Wh	800 Ah	400 Ah	200 Ah
10,000 Wh	833 Ah	417 Ah	208 Ah
13,500 Wh	1,125 Ah	563 Ah	281 Ah

Notice how the same energy requires dramatically different Ah ratings depending on voltage. This is the fundamental reason higher-voltage systems are preferred for larger installations -- less current means simpler, cheaper wiring.

Practical Example: Tesla Powerwall

The Tesla Powerwall 3 stores 13,500 Wh (13.5 kWh) and operates at a nominal 48V.

Ah = 13,500 / 48 = 281 Ah

This means the Powerwall can deliver 281 amps for one hour, or 28.1 amps for 10 hours, or 11.7 amps for 24 hours -- all at 48V. In practice, the Powerwall's built-in inverter handles the DC-to-AC conversion, so you never interact with the DC amp rating directly. But if you were building an equivalent DIY battery bank at 48V, you would need 281 Ah of capacity.

To match that with 12V batteries in series (four 12V batteries for 48V), each battery would still need to be 281 Ah -- series wiring does not change the Ah rating, only the voltage.

How Series vs Parallel Wiring Affects Ah and Wh

Understanding how battery wiring affects amp-hours is essential when designing a bank.

Series Wiring: Voltage Adds, Ah Stays the Same

Connect batteries positive-to-negative in a chain. Voltage adds up; amp-hours remain unchanged.

Configuration	Voltage	Ah	Total Wh
1x 12V 100Ah	12V	100 Ah	1,200 Wh
2x 12V 100Ah (series)	24V	100 Ah	2,400 Wh
4x 12V 100Ah (series)	48V	100 Ah	4,800 Wh

Parallel Wiring: Ah Adds, Voltage Stays the Same

Connect all positives together and all negatives together. Ah adds up; voltage remains unchanged.

Configuration	Voltage	Ah	Total Wh
1x 12V 100Ah	12V	100 Ah	1,200 Wh
2x 12V 100Ah (parallel)	12V	200 Ah	2,400 Wh
4x 12V 100Ah (parallel)	12V	400 Ah	4,800 Wh

Series-Parallel: Both Add

For large systems, you combine both. Four 12V 100Ah batteries wired as two series strings of two in parallel: 24V, 200 Ah, 4,800 Wh.

The key takeaway: total energy (Wh) is always the same regardless of wiring configuration (assuming the same number of identical batteries). Wiring only changes the voltage and current at which that energy is delivered.

Why Higher Voltage Means Lower Amps (And Why That Matters)

When you convert 10,000 Wh to Ah at different voltages, the numbers diverge dramatically:

10,000 Wh at 12V = 833 Ah
10,000 Wh at 24V = 417 Ah
10,000 Wh at 48V = 208 Ah

Lower current means:

Thinner wires. NEC wire sizing is based on amperage. At 833A you need massive 4/0 cables or larger. At 208A, you can use 2/0 or smaller depending on run length.
Smaller fuses and breakers. A 250A class-T fuse costs $15-30. An 800A+ fuse is harder to source and more expensive.
Less voltage drop. Voltage drop is proportional to current. At 48V with 208A, voltage drop over a 10-foot cable run is one-quarter of what it would be at 12V with 833A.
Higher efficiency. Less current flowing through wires means less energy lost as heat (I-squared-R losses).

This is why virtually all modern whole-home battery systems (Tesla Powerwall, Enphase IQ, EG4, Sol-Ark) operate at 48V -- and why utility-scale storage operates at hundreds of volts.

Sizing a Charge Controller Using Wh to Ah

Suppose your solar array produces 3,000 Wh per day and charges a 48V battery bank.

Step 1 -- Convert daily Wh to Ah: 3,000 / 48 = 62.5 Ah per day

Step 2 -- Determine peak charging current. If you get 5 peak sun hours, the average charge rate is 62.5 / 5 = 12.5A. But solar output is not perfectly flat -- peak current may be 1.3-1.5x the average. So expect peak current around 16-19A.

Step 3 -- Select the charge controller. A 30A MPPT controller handles this comfortably. A 20A controller would work at average output but could clip during peak production. Always round up to the next standard size.

For a 12V system delivering the same 3,000 Wh: 3,000 / 12 = 250 Ah per day, with peak current around 65-75A. You would need a 100A charge controller -- significantly more expensive than the 30A unit for the 48V system.

Wire Gauge Selection

After converting to Ah, you can determine the maximum current your system handles and select appropriate wire gauge. Here is a simplified reference for common battery bank currents:

Max Current	Copper Wire Gauge (AWG)	Typical Use
30A or under	10 AWG	Small 12V systems
30-55A	6 AWG	Mid-size 12V, small 24V
55-75A	4 AWG	Large 12V, mid-size 24V
75-100A	2 AWG	24V systems
100-150A	1/0 AWG	48V whole-home
150-200A	2/0 AWG	Large 48V systems
200-250A	3/0 AWG	High-capacity 48V

These are approximate for short runs (under 10 feet). Longer cable runs require upsizing. Always follow NEC Article 690 for solar PV systems and consult a licensed electrician for permanent installations.