Kwh to Ah Calculator

kWh to Ah Calculator

Convert Kilowatt-hours to Amp-hours based on battery voltage.

12V 24V 36V 48V 120V 240V Custom Voltage

Default is 100% (ideal conversion).

Total Capacity: 0 Ah

How to Convert kWh to Ah

Converting Kilowatt-hours (kWh) to Amp-hours (Ah) is essential when sizing batteries for solar systems, electric vehicles, or UPS backups. Because kWh measures energy and Ah measures charge, you must know the nominal voltage of the system to complete the calculation.

The Formula

Ah = (kWh × 1,000) / Voltage

Step-by-Step Example

Suppose you have a 5 kWh battery system operating at 48 Volts. To find the Amp-hour rating:

1. Convert kWh to Watt-hours: 5 kWh × 1,000 = 5,000 Wh.
2. Divide by the Voltage: 5,000 Wh / 48V = 104.17 Ah.
3. If considering an 85% efficiency rate: 104.17 / 0.85 = 122.55 Ah.

Why Efficiency Matters

In real-world applications, energy is lost through heat and chemical conversion. When calculating how much battery capacity you need to store a certain amount of energy, you should divide the result by the efficiency decimal (e.g., 0.9 for 90%) to ensure you don't undersize your battery bank.

document.getElementById('voltageInput').onchange = function() { var customDiv = document.getElementById('customVoltContainer'); if (this.value === 'custom') { customDiv.style.display = 'block'; } else { customDiv.style.display = 'none'; } }; function calculateAh() { var kwh = parseFloat(document.getElementById('energyInput').value); var efficiency = parseFloat(document.getElementById('efficiency').value); var selectedVolt = document.getElementById('voltageInput').value; var voltage; if (selectedVolt === 'custom') { voltage = parseFloat(document.getElementById('customVoltage').value); } else { voltage = parseFloat(selectedVolt); } if (isNaN(kwh) || isNaN(voltage) || voltage <= 0 || kwh < 0) { alert('Please enter valid positive numbers for Energy and Voltage.'); return; } if (isNaN(efficiency) || efficiency 100) { efficiency = 100; } // Calculation: Ah = (kWh * 1000) / (Voltage * (Efficiency/100)) // To find needed capacity to store kWh: Ah = (kWh * 1000) / Voltage / (Eff/100) var effDecimal = efficiency / 100; var ah = (kwh * 1000) / (voltage * effDecimal); var resultElement = document.getElementById('ahResult'); var formulaElement = document.getElementById('formulaUsed'); var resultArea = document.getElementById('resultArea'); resultElement.innerText = ah.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2}) + ' Ah'; var formulaText = '(' + kwh + ' kWh × 1000) / ' + voltage + 'V'; if (efficiency < 100) { formulaText += ' (adjusted for ' + efficiency + '% efficiency)'; } formulaElement.innerText = 'Formula: ' + formulaText; resultArea.style.display = 'block'; }