kWh to Ah Converter: Calculate Energy to Battery Capacity

How to Use Our kWh to Ah Converter

To find the amp-hour capacity of your battery system, you only need two key values. Both are fundamental specifications for any battery system.

• Energy (in kWh): Enter the total energy storage capacity of your battery or system in kilowatt-hours. For example, a home solar battery might be 10 kWh; an EV battery could be 75 kWh.

• Voltage (in Volts): Enter the nominal voltage (V) of your battery system. This is crucial as amp-hours are dependent on voltage. Common DC system voltages are 12V, 24V, or 48V for solar and RV systems.

Once you provide both values, the calculator will immediately show the equivalent capacity in Amp-hours (Ah).

Understanding Your Results

The result from the calculator is your battery’s capacity in Amp-hours (Ah). While kWh tells you the total energy in the battery, Ah tells you its charge capacity at a specific voltage. This is vital for system design and runtime calculations.

• Kilowatt-hour (kWh): Think of kWh as the total amount of energy stored in the tank. This is the same unit used on your home electricity bill and is the best way to compare the overall energy content of different battery systems. 1 kWh is equal to 1,000 watt-hours.

• Voltage (V): Think of voltage as the pressure or force of the electrical system. In battery systems, devices are designed to run at a specific voltage (e.g., 12V for many RV appliances).

• Amp-hour (Ah): Think of Ah as the size of the fuel tank measured in terms of charge. It tells you how many amps a battery can deliver for how many hours. For example, a 100 Ah battery can theoretically provide 10 amps for 10 hours.

The formula used by the calculator is:

We multiply by 1,000 to convert kilowatt-hours to watt-hours before dividing by the voltage.

Why Both kWh and Ah Matter

kWh and Ah provide two different but equally important views of your battery.

Notice how the Home Solar Battery has more than eight times the energy (kWh) of the RV battery, but only about double the amp-hours (Ah). This is because it operates at a much higher, more efficient voltage.

Frequently Asked Questions

### What’s the main difference between Ah and kWh?

The simplest way to think about it is:

• kWh (Energy): Measures the total work that can be done. It’s the “what.” A 10 kWh battery holds twice as much energy as a 5 kWh battery, period.

• Ah (Charge Capacity): Measures how that energy is delivered. It’s the “how.” A 200 Ah battery can deliver twice the current of a 100 Ah battery at the same voltage.

You need both. kWh tells you your total energy reserve. Ah is crucial for sizing wires, fuses, and determining how long you can run appliances that have a specific amp draw.

### Why do I need to know the voltage for this conversion?

Voltage is the essential link between energy (kWh) and charge capacity (Ah). Because Watts = Volts × Amps, you cannot determine the amps without knowing the volts. A system can have a huge energy capacity (kWh) but a relatively small amp-hour capacity if it runs at a very high voltage, like in an electric car. Conversely, a low-voltage system (like in an RV) needs a very high amp-hour capacity to store the same amount of energy.

### How does this calculation relate to solar panel systems?

This is a core calculation for solar energy.

1. First, you determine your daily energy needs in kWh. (e.g., you need to run appliances totaling 3 kWh per day).

2. Then, you buy a battery bank to store that energy (e.g., a 5 kWh battery to have a reserve).

3. Finally, you use this converter to find the Ah capacity needed based on your chosen system voltage (12V, 24V, or 48V). A 5 kWh battery bank run at 48V is (5 * 1000) / 48 = 104 Ah. This Ah value helps you select the right charge controller and battery monitoring system.

### How many amp-hours is a Tesla Model 3 battery?

This is a perfect example of why voltage is critical. A Tesla Model 3 Long Range has roughly a 75 kWh battery pack that operates at a nominal voltage of about 400V.

Using the calculator: (75 kWh * 1000) / 400V = 187.5 Ah.

While 187.5 Ah might not sound huge compared to some RV batteries, it’s at an incredibly high voltage, which is why it holds so much total energy (kWh).

How do I calculate how long my battery bank will actually last?

The simple formula is Time = Amp-hours / Amp Draw. However, real-world battery life is affected by two main factors:

1. Efficiency Losses: You lose energy when converting DC battery power to AC power for your appliances (through an inverter). You should account for about a 10-15% loss.

2. Peukert’s Law: This law states that the faster you discharge a battery, the less total capacity it has. A battery rated at 100 Ah (at a 20-hour discharge rate) might only give you 70 Ah of capacity if you discharge it very quickly in 1 hour. Always check the battery’s spec sheet for its capacity at different discharge rates (C-rates).

What is C-Rate and how does it relate to Ah?

The C-Rate describes how quickly a battery is charged or discharged relative to its maximum capacity.

• 1C: A 1C discharge rate on a 100 Ah battery means you are drawing 100 amps, and it would theoretically be empty in 1 hour.

• C/20 or 0.05C: This is a common rating for deep-cycle batteries. It means drawing 5 amps from a 100 Ah battery (100 Ah / 20 hours = 5A), and it would last for 20 hours.

A battery’s usable Ah capacity is often highest at a low C-rate.

How does temperature affect a battery’s Ah capacity?

Temperature has a significant impact, especially on lead-acid batteries.

• Cold Temperatures: Chemical reactions inside the battery slow down, which reduces its effective Ah capacity. A battery might only offer 50% of its rated capacity at freezing temperatures.

• Hot Temperatures: Capacity might slightly increase, but high temperatures drastically shorten the battery’s overall lifespan by accelerating internal degradation.

What is the difference between Amp-hours (Ah) and Milliamp-hours (mAh)?

Milliamp-hours are simply a smaller unit of charge capacity. “Milli-” means one-thousandth.

• 1 Ah = 1,000 mAh

mAh is used for small consumer electronics like phones and power banks (e.g., a 5,000 mAh phone battery). Ah is used for large batteries in vehicles, boats, and off-grid systems (e.g., a 100 Ah deep-cycle battery).

Why is my utility bill in kWh but my RV battery is in Ah?

They are describing two different things for two different purposes.

• Your utility bill (kWh) measures the total amount of energy you consumed from an essentially limitless source (the grid). The voltage is fixed and constant (e.g., 240V), so only the total energy matters.

• Your RV battery (Ah) describes its finite charge capacity at a specific, low voltage (e.g., 12V). In an RV, you run many 12V devices, so knowing how many amps you can draw and for how long (Ah) is more practical for day-to-day use than knowing the total energy in kWh.

I have four 100 Ah 12V batteries. What is my total kWh?

This depends on how you wire them.

• Wired in Parallel (12V system): The voltage stays at 12V, and the amp-hours add up. You have a 400 Ah, 12V bank. The energy is (400 Ah * 12V) / 1000 = 4.8 kWh.

• Wired in Series (48V system): The amp-hours stay at 100 Ah, and the voltage adds up. You have a 100 Ah, 48V bank. The energy is (100 Ah * 48V) / 1000 = 4.8 kWh.

Notice the total energy (kWh) is the same either way! You are just configuring it for different system requirements.

Now that you’ve determined your system’s amp-hour capacity, you may want to estimate how long it can run your appliances. Check out our Battery Life Calculator for detailed runtime estimates. To understand the relationship between a battery’s charge and energy in smaller devices, use our mAh to Wh Converter.