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Convert Kilojoules to Kilowatt Hours - Energy Converter

This converter translates energy values from kilojoules (kJ) to kilowatt-hours (kWh) using the International System of Units (SI) definitions. It applies the fixed, physics-based relationship between joules, watts, and seconds to produce exact conversions appropriate for engineering, laboratory, and regulatory workflows.

The tool is intended for quick, authoritative conversions and for use as a verification step when preparing energy inventories, lab reports, or performance calculations. For measurement-grade work, follow instrument calibration guidance and report results with appropriate significant figures and uncertainty.

Updated Nov 1, 2025

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Methodology

The conversion is derived from SI definitions: 1 watt equals 1 joule per second (1 W = 1 J/s). A kilowatt-hour is the energy delivered by 1 kilowatt acting for one hour: 1 kWh = 1000 W × 3600 s = 3,600,000 J.

Expressed in kilojoules, 1 kWh = 3,600 kJ. Therefore to convert kilojoules to kilowatt-hours, divide the kilojoule value by 3,600. This relationship is exact within the SI system and is documented by standards authorities.

For applied and regulatory use, record the number of significant figures supported by your measurement device and, where needed, include instrument calibration traceability (for example, NIST-traceable certificates) and uncertainty estimates in reports.

Worked examples

3600 kJ → 3600 ÷ 3600 = 1 kWh

9000 kJ → 9000 ÷ 3600 = 2.5 kWh

150 kJ → 150 ÷ 3600 ≈ 0.0416667 kWh (report with appropriate sig figs)

Expert Q&A

What is the exact conversion factor between kJ and kWh?

Exactly 1 kWh = 3,600 kJ, so use kWh = kJ / 3600.

How do I convert kilojoules per hour (kJ/h) to kilowatts (kW)?

Convert kJ/h to watts by noting 1 kJ = 1000 J and 1 hour = 3600 s. So 1 kJ/h = 1000 J / 3600 s ≈ 0.277777... W, which is 0.000277777... kW. For kJ/h → kW multiply by 0.0002777777778.

How many significant figures should I report?

Match the precision to the upstream measurement device and the purpose of the calculation. For engineering audits and instrument readings, report the same number of significant digits as the instrument supports and include uncertainty or calibration status when required by standards or regulatory guidance.

Does this conversion account for measurement uncertainty or meter efficiency?

No. This converter performs a fixed-unit arithmetic conversion only. For real-world energy measurements, account separately for meter accuracy, instrument calibration, measurement uncertainty, and any system losses or efficiencies.

Where should I cite the conversion in technical documents?

Cite an authoritative SI reference or standards guidance (for example, national metrology institutes or ISO standards) and include the conversion formula kWh = kJ ÷ 3600 in your methods section. If measurements are used for compliance, include calibration traceability and uncertainty statements.

Sources & citations