Energy Conversion   | Kilowatt-hour (kWh) → Joule (J)

Supported Units

Name	Description	Conversions
Watt-hour (Wh)	The Watt-hour (Wh) is a unit of energy, representing the amount of energy consumed or produced by a device with a power consumption of one watt over the course of one hour. It is commonly used to measure electrical energy in devices such as batteries, electrical appliances and power grids. Conversions: 1 watt-hour (Wh) = 1 watt x 1 hour Common Uses: Electrical Energy Consumption Measures the energy used by electrical devices (e.g., light bulbs, computers and appliances). Batteries Used to describe the energy capacity of batteries, such as those in laptops, phones or electric vehicles. Energy Meters Often used by utility companies to bill consumers for electricity usage.	1 Wh = 1e-3 kWh 1 Wh = 1e-6 MWh 1 Wh = 1e-9 GWh 1 Wh = 2.2469432668e+22 eV 1 Wh = 2.2469432668e+16 MeV 1 Wh = 3.4121416319e+0 BTU 1 Wh = 3.4121416319e-3 kBTU 1 Wh = 3.6e+3 J 1 Wh = 3.6e+0 KJ 1 Wh = 3.6e-3 MJ 1 Wh = 3.6e-6 GJ 1 Wh = 8.604206501e+2 gram-cal 1 Wh = 8.604206501e-1 [k]cal
Kilowatt-hour (kWh)	The Kilowatt-hour (kWh) is a unit of energy commonly used to measure electricity consumption. It represents the amount of energy used by a device with a power consumption of one kilowatt over the course of one hour. Conversions: 1 kilowatt-hour (kWh) = 1,000 watt-hours (Wh) Common Uses: Electricity Billing Utility companies use kWh to calculate energy usage and bill consumers for electricity consumption. Energy Consumption Tracking Measures energy use in households, businesses and industrial settings (e.g., lighting, heating and appliances). Renewable Energy Used to measure the energy output of solar panels, wind turbines and other renewable sources.	1 kWh = 1e+3 Wh 1 kWh = 1e-3 MWh 1 kWh = 1e-6 GWh 1 kWh = 2.2469432668e+25 eV 1 kWh = 2.2469432668e+19 MeV 1 kWh = 3.4121416319e+3 BTU 1 kWh = 3.4121416319e+0 kBTU 1 kWh = 3.6e+6 J 1 kWh = 3.6e+3 KJ 1 kWh = 3.6e+0 MJ 1 kWh = 3.6e-3 GJ 1 kWh = 8.604206501e+5 gram-cal 1 kWh = 8.604206501e+2 [k]cal
Megawatt-hour (MWh)	The Megawatt-hour (MWh) is a unit of energy equal to 1,000 kilowatt-hours (kWh) or 1 million watt-hours (Wh). It is commonly used to measure large amounts of electrical energy, especially in power generation, utilities and large-scale energy systems. Conversions: 1 megawatt-hour (MWh) = 1,000 kilowatt-hours (kWh) Common Uses: Power Generation Measures the amount of electricity produced by power plants or renewable energy sources like wind or solar over time. Electricity Grids Used to track and manage energy distribution and consumption across power grids. Energy Industry Often used in industrial settings or large-scale energy contracts.	1 MWh = 1e+6 Wh 1 MWh = 1e+3 kWh 1 MWh = 1e-3 GWh 1 MWh = 2.2469432668e+28 eV 1 MWh = 2.2469432668e+22 MeV 1 MWh = 3.4121416319e+6 BTU 1 MWh = 3.4121416319e+3 kBTU 1 MWh = 3.6e+9 J 1 MWh = 3.6e+6 KJ 1 MWh = 3.6e+3 MJ 1 MWh = 3.6e+0 GJ 1 MWh = 8.604206501e+8 gram-cal 1 MWh = 8.604206501e+5 [k]cal
Gigawatt-hour (GWh)	The Gigawatt-hour (GWh) is a unit of energy equal to 1,000 megawatt-hours (MWh) or 1 million kilowatt-hours (kWh). It is typically used to measure vast amounts of electricity generated or consumed over time, especially in large-scale power generation and energy systems. Conversions: 1 gigawatt-hour (GWh) = 1,000 megawatt-hours (MWh) Common Uses: Power Plants Measures the electricity output of large power plants or renewable energy facilities (e.g., wind farms, solar parks). Electricity Grids Used to track large-scale energy distribution and demand on national or regional power grids. Energy Consumption Used in industries, cities and large organizations to measure electricity consumption over extended periods.	1 GWh = 1e+9 Wh 1 GWh = 1e+6 kWh 1 GWh = 1e+3 MWh 1 GWh = 2.2469432668e+31 eV 1 GWh = 2.2469432668e+25 MeV 1 GWh = 3.4121416319e+9 BTU 1 GWh = 3.4121416319e+6 kBTU 1 GWh = 3.6e+12 J 1 GWh = 3.6e+9 KJ 1 GWh = 3.6e+6 MJ 1 GWh = 3.6e+3 GJ 1 GWh = 8.604206501e+11 gram-cal 1 GWh = 8.604206501e+8 [k]cal
Electronvolt (eV)	The Electronvolt (eV) is a unit of energy commonly used in physics, particularly in atomic and particle physics. It represents the amount of kinetic energy gained or lost by an electron when it is accelerated through an electric potential difference of one volt. Conversions: 1 eV = 1.602176634 x 10-19 joules (J) Common Uses: Particle Physics Measures the energy of particles in accelerators and interactions in subatomic physics. Atomic and Molecular Physics Used to describe energy levels in atoms, molecules and electron transitions. Solid-State Physics Measures the energy involved in processes like electron movement in semiconductors.	1 eV = 4.45049065e-23 Wh 1 eV = 4.45049065e-26 kWh 1 eV = 4.45049065e-29 MWh 1 eV = 4.45049065e-32 GWh 1 eV = 1e-6 MeV 1 eV = 1.5185704429e-22 BTU 1 eV = 1.5185704429e-25 kBTU 1 eV = 1.602176634e-19 J 1 eV = 1.602176634e-22 KJ 1 eV = 1.602176634e-25 MJ 1 eV = 1.602176634e-28 GJ 1 eV = 3.8292940583e-20 gram-cal 1 eV = 3.8292940583e-23 [k]cal
Mega electronvolt (MeV)	The Mega electronvolt (MeV) is a unit of energy equal to 1 million electronvolts (eV) or 1 x 106 eV. It is commonly used in particle physics and nuclear physics to measure the energy of particles or the energy released in nuclear reactions. Conversions: 1 MeV = 1,000,000 eV = 1 x 106 eV 1 MeV = 1.602176634 x 10-13 joules (J) Common Uses: Particle Physics Measures the energy of subatomic particles in particle accelerators or collisions. Nuclear Physics Used to quantify the energy involved in nuclear reactions, such as fission and fusion. Medical Applications Used in radiation therapy for cancer treatment and in diagnostic imaging techniques like PET scans.	1 MeV = 4.45049065e-17 Wh 1 MeV = 4.45049065e-20 kWh 1 MeV = 4.45049065e-23 MWh 1 MeV = 4.45049065e-26 GWh 1 MeV = 1e+6 eV 1 MeV = 1.5185704429e-16 BTU 1 MeV = 1.5185704429e-19 kBTU 1 MeV = 1.602176634e-13 J 1 MeV = 1.602176634e-16 KJ 1 MeV = 1.602176634e-19 MJ 1 MeV = 1.602176634e-22 GJ 1 MeV = 3.8292940583e-14 gram-cal 1 MeV = 3.8292940583e-17 [k]cal
British Thermal Unit (BTU)	The British Thermal Unit (BTU) is a unit of energy used to measure heat. It represents the amount of energy required to raise the temperature of one pound of water by one degree Fahrenheit. One Btu equals approximately 1,055 J (varying within the range of 1,054 - 1,060 J depending on the definition of BTU) Conversions: 1 BTU ≈ 1,055 joules (J) Common Uses: Heating and Cooling Measures the energy used in heating systems, air conditioners and refrigerators. Energy Industry Used to quantify the energy content of fuels like natural gas, oil and coal. Appliances Commonly found in the specifications of HVAC systems, water heaters and stoves.	1 BTU = 2.9307107028e-1 Wh 1 BTU = 2.9307107028e-4 kWh 1 BTU = 2.9307107028e-7 MWh 1 BTU = 2.9307107028e-10 GWh 1 BTU = 6.5851406806e+21 eV 1 BTU = 6.5851406806e+15 MeV 1 BTU = 1e-3 kBTU 1 BTU = 1.055055853e+3 J 1 BTU = 1.055055853e+0 KJ 1 BTU = 1.055055853e-3 MJ 1 BTU = 1.055055853e-6 GJ 1 BTU = 2.5216440081e+2 gram-cal 1 BTU = 2.5216440081e-1 [k]cal
Kilo British Thermal Unit (kBTU)	The Kilo British Thermal Unit (kBTU) is a unit of energy equal to 1,000 BTUs (British Thermal Units). It is commonly used to measure larger quantities of heat energy, especially in heating, ventilation, air conditioning (HVAC) and energy systems. Conversions: 1 kBTU = 1,000 BTUs 1 kBTU ≈ 1,055,000 joules (J) Common Uses: Heating and Cooling Systems Measures the energy output of furnaces, air conditioners and heat pumps. Energy Production Used to quantify energy content in fuels like natural gas and coal. Industrial Applications Used to assess energy efficiency and fuel consumption in large-scale operations.	1 kBTU = 2.9307107028e+2 Wh 1 kBTU = 2.9307107028e-1 kWh 1 kBTU = 2.9307107028e-4 MWh 1 kBTU = 2.9307107028e-7 GWh 1 kBTU = 6.5851406806e+24 eV 1 kBTU = 6.5851406806e+18 MeV 1 kBTU = 1e+3 BTU 1 kBTU = 1.055055853e+6 J 1 kBTU = 1.055055853e+3 KJ 1 kBTU = 1.055055853e+0 MJ 1 kBTU = 1.055055853e-3 GJ 1 kBTU = 2.5216440081e+5 gram-cal 1 kBTU = 2.5216440081e+2 [k]cal
Joule (J)	The Joule (J) is the SI (International System of Units) unit of energy, work or heat. It represents the amount of energy transferred when one newton of force is applied over a distance of one meter or the energy used when one ampere of electric current passes through a resistance of one ohm for one second. Conversions: 1 joule (J) = 1 newton meter (N x m) = 1 watt second (W x s) Common Uses: Energy Measures energy in electrical systems, heat and mechanical work. Physics Used to quantify the energy involved in physical processes, such as kinetic or potential energy. Heat Measures heat energy in thermodynamics and chemistry.	1 J = 2.7777777778e-4 Wh 1 J = 2.7777777778e-7 kWh 1 J = 2.7777777778e-10 MWh 1 J = 2.7777777778e-13 GWh 1 J = 6.2415090745e+18 eV 1 J = 6.2415090745e+12 MeV 1 J = 9.4781711997e-4 BTU 1 J = 9.4781711997e-7 kBTU 1 J = 1e-3 KJ 1 J = 1e-6 MJ 1 J = 1e-9 GJ 1 J = 2.3900573614e-1 gram-cal 1 J = 2.3900573614e-4 [k]cal
Kilojoule (KJ)	The Kilojoule (KJ) is a unit of energy equal to 1,000 joules (J). It is commonly used to measure larger quantities of energy, particularly in fields like nutrition, thermodynamics and industrial processes. Conversions: 1 kilojoule (kJ) = 1,000 joules (J) Common Uses: Nutrition Measures the energy content of food (e.g., food labels often display energy in kJ). Energy Systems Used to quantify energy in electricity, heating and cooling systems. Industrial Applications Measures energy in mechanical work, heating processes and fuel consumption.	1 KJ = 2.7777777778e-1 Wh 1 KJ = 2.7777777778e-4 kWh 1 KJ = 2.7777777778e-7 MWh 1 KJ = 2.7777777778e-10 GWh 1 KJ = 6.2415090745e+21 eV 1 KJ = 6.2415090745e+15 MeV 1 KJ = 9.4781711997e-1 BTU 1 KJ = 9.4781711997e-4 kBTU 1 KJ = 1e+3 J 1 KJ = 1e-3 MJ 1 KJ = 1e-6 GJ 1 KJ = 2.3900573614e+2 gram-cal 1 KJ = 2.3900573614e-1 [k]cal
Megajoule (MJ)	The Megajoule (MJ) is a unit of energy equal to 1 million joules (J). It is commonly used to measure larger quantities of energy, particularly in fields like power generation, industrial processes and fuel energy content. Conversions: 1 mega joule (MJ) = 1,000,000 joules (J) Common Uses: Power Generation Measures the energy produced or consumed by power plants and electrical systems. Fuel Energy Used to describe the energy content of fuels, such as natural gas, coal and biofuels. Engineering Used in mechanical systems to quantify large amounts of energy, work or heat.	1 MJ = 2.7777777778e+2 Wh 1 MJ = 2.7777777778e-1 kWh 1 MJ = 2.7777777778e-4 MWh 1 MJ = 2.7777777778e-7 GWh 1 MJ = 6.2415090745e+24 eV 1 MJ = 6.2415090745e+18 MeV 1 MJ = 9.4781711997e+2 BTU 1 MJ = 9.4781711997e-1 kBTU 1 MJ = 1e+6 J 1 MJ = 1e+3 KJ 1 MJ = 1e-3 GJ 1 MJ = 2.3900573614e+5 gram-cal 1 MJ = 2.3900573614e+2 [k]cal
Gigajoule (GJ)	The Gigajoule (GJ) is a unit of energy equal to 1 billion joules (J). It is commonly used to measure very large quantities of energy, especially in industries like energy production, heating and large-scale manufacturing. Conversions: 1 gigajoule (GJ) = 1,000,000,000 joules (J) Common Uses: Energy Production Used to quantify energy output from power plants or large renewable energy sources like wind or solar. Fuel Consumption Measures the energy content of fuels, such as natural gas, coal or oil. Industrial Applications Used in processes that require significant amounts of energy, such as heating, manufacturing and mining.	1 GJ = 2.7777777778e+5 Wh 1 GJ = 2.7777777778e+2 kWh 1 GJ = 2.7777777778e-1 MWh 1 GJ = 2.7777777778e-4 GWh 1 GJ = 6.2415090745e+27 eV 1 GJ = 6.2415090745e+21 MeV 1 GJ = 9.4781711997e+5 BTU 1 GJ = 9.4781711997e+2 kBTU 1 GJ = 1e+9 J 1 GJ = 1e+6 KJ 1 GJ = 1e+3 MJ 1 GJ = 2.3900573614e+8 gram-cal 1 GJ = 2.3900573614e+5 [k]cal
Gram calorie (gram-cal)	The Gram calorie (gram-cal) also simply known as the calorie, is a unit of energy that represents the amount of heat required to raise the temperature of one milliliter of water by one degree Celsius (°C). Conversions: 1 gram calorie (gram-cal) = 4.184 joules (J) Common Uses: Nutrition Historically used to measure the energy content in food, though it is now largely replaced by the kilocalorie (kcal) in nutritional labeling. Physics and Chemistry Measures heat energy in scientific experiments, particularly in thermodynamics and calorimetry.	1 gram-cal = 1.1622222222e-3 Wh 1 gram-cal = 1.1622222222e-6 kWh 1 gram-cal = 1.1622222222e-9 MWh 1 gram-cal = 1.1622222222e-12 GWh 1 gram-cal = 2.6114473968e+19 eV 1 gram-cal = 2.6114473968e+13 MeV 1 gram-cal = 3.96566683e-3 BTU 1 gram-cal = 3.96566683e-6 kBTU 1 gram-cal = 4.184e+0 J 1 gram-cal = 4.184e-3 KJ 1 gram-cal = 4.184e-6 MJ 1 gram-cal = 4.184e-9 GJ 1 gram-cal = 1e-3 [k]cal
Kilo calorie ([k]cal)	The Kilo calorie ([k]cal) is a unit of energy that represents the amount of heat required to raise the temperature of one liter of water by one degree Celsius (°C). It is commonly used to measure energy, particularly in food and nutrition. Conversions: 1 calorie ([k]cal) = 4184 joules (J) Common Uses: Nutrition Measures the energy content in food and beverages. Science and Thermodynamics Used to quantify heat in laboratory experiments and calorimetry.	1 [k]cal = 1.1622222222e+0 Wh 1 [k]cal = 1.1622222222e-3 kWh 1 [k]cal = 1.1622222222e-6 MWh 1 [k]cal = 1.1622222222e-9 GWh 1 [k]cal = 2.6114473968e+22 eV 1 [k]cal = 2.6114473968e+16 MeV 1 [k]cal = 3.96566683e+0 BTU 1 [k]cal = 3.96566683e-3 kBTU 1 [k]cal = 4.184e+3 J 1 [k]cal = 4.184e+0 KJ 1 [k]cal = 4.184e-3 MJ 1 [k]cal = 4.184e-6 GJ 1 [k]cal = 1e+3 gram-cal

Why So Many Units for One Quantity

Energy is a single physical quantity, but each field developed its own unit before the connection between heat, work, and electricity was understood. Chemists measured heat in calories, engineers measured it in British thermal units, electrical utilities billed in watt-hours, and physicists working with particles needed something far smaller.

All of them measure the same thing, and all convert to joules by a fixed factor. The joule is the SI unit and the natural common ground: one joule is the work done by a force of one newton acting over one meter.

The Units in Practice

Joule

The SI unit, and the reference every other unit here converts through. A joule is a small amount on a human scale — roughly the energy needed to lift an apple one meter — so practical quantities are usually expressed in kilojoules or megajoules.

Watt-hour and kilowatt-hour

Energy expressed as power sustained over time. One watt for one hour is 3,600 joules, since a watt is one joule per second. The kilowatt-hour is the unit on your electricity bill, and megawatt-hours and gigawatt-hours scale it up for generation and grid figures.

Calorie and kilocalorie

Originally the heat required to raise one gram of water by one degree Celsius. The gram calorie is 4.184 joules. The kilocalorie is a thousand of those — and it is what food labels mean, whether they print "Calories" or "kcal".

British thermal unit

The heat needed to raise one pound of water by one degree Fahrenheit, about 1,055 joules. It remains standard for heating and air conditioning equipment, especially in the United States, where boiler and air conditioner capacity is quoted in BTU or kBTU.

Electronvolt

The energy an electron gains crossing a potential difference of one volt: about 1.602 × 10⁻¹⁹ joules. It is the natural unit for atomic and particle physics, where joules would mean writing impractically small numbers. Chemical bonds are a few eV; nuclear processes run to MeV.

A Note on Food Calories

This causes real confusion. The "calorie" on a nutrition label is a kilocalorie — one thousand of the calories used in physics and chemistry. A 250-calorie snack contains 250 kilocalories, which is about 1,046 kilojoules.

The convention is to capitalize the food unit as "Calorie" and leave the scientific one lowercase, but this is followed inconsistently and is invisible in speech. Labels in the European Union and Australia sidestep the problem by printing kilojoules alongside, which is why the same product can show both 250 kcal and 1,046 kJ.

Worked Examples

• A 60 W bulb left on for 10 hours — 600 watt-hours, or 0.6 kWh, or 2.16 megajoules.
• A 2,000 kcal daily diet — about 8,368 kilojoules.
• A 12,000 BTU air conditioner — about 12.66 megajoules per hour, or roughly 3.5 kW of cooling.
• A month of household electricity at 300 kWh — 1.08 gigajoules.
• A typical chemical bond at 4 eV — about 6.4 × 10⁻¹⁹ joules per bond.

Common Uses

• Electricity bills — understanding kilowatt-hours and what an appliance actually costs to run.
• Heating and cooling — comparing equipment rated in BTU against equipment rated in kilowatts.
• Nutrition — converting between kilocalories and kilojoules on food labels.
• Physics and chemistry — bond energies, reaction enthalpies, and particle energies.
• Engineering — reconciling datasheets written in different unit conventions.
• Energy reporting — comparing consumption figures published in joules, kWh, or BTU.

Frequently Asked Questions

What is the difference between energy and power?

Power is the rate of energy transfer; energy is the total amount. A watt is one joule per second, so a watt is power and a watt-hour is energy. This is why an appliance is rated in watts but billed in kilowatt-hours.

Is a food Calorie the same as a calorie?

No — it is a thousand of them. The nutritional Calorie is a kilocalorie. Every figure on a food label uses this larger unit, so select kilocalorie when converting from nutritional information.

How much is a kilowatt-hour?

Exactly 3.6 megajoules. As a practical sense of scale, it will run a typical refrigerator for most of a day, or a 100 W device for ten hours.

Why do physicists use electronvolts?

Convenience of scale. The energies involved in atomic and subatomic processes are around 10⁻¹⁹ joules, so expressing them in joules means constant scientific notation. In electronvolts the same quantities become small, readable numbers.

Are BTU figures on appliances energy or power?

Usually power, despite appearances. Air conditioners and heaters are typically rated in BTU per hour even when the label just says "BTU", so a 12,000 BTU unit means 12,000 BTU per hour. Check the specification if the distinction matters for your calculation.