Energy Converter

Energy is the capacity to do work. The SI base unit of energy is the joule (J), named after the British physicist James Prescott Joule. One joule is the energy expended when a force of 1 newton moves an object by 1 metre. The joule is a very small unit – lifting a 100-gram object by 1 metre costs about 1 joule. In everyday use, therefore, values are usually given in kilojoules (kJ = 1,000 J) or megajoules (MJ = 1,000,000 J).

In the field of electricity and energy supply, the kilowatt-hour (kWh) dominates. 1 kWh is the energy a 1,000-watt appliance consumes in one hour: 1 kWh = 1,000 W × 3,600 s = 3,600,000 J = 3.6 MJ. Your electricity bill shows consumption in kWh, and the price per kWh in Germany is typically 30–40 cents. A household with 3,000 kWh of annual consumption pays around 900–1,200 euros for electricity. Renewable energy sources such as solar panels and wind farms are also measured in kWh or megawatt-hours (MWh).

In nutritional science, calories are used – more precisely, kilocalories (kcal), sometimes called "large calories". 1 kcal is the amount of heat needed to raise the temperature of 1 kg of water by 1 kelvin: 1 kcal = 4,184 J. In the EU, food packaging shows energy content in both kJ and kcal. A daily calorie requirement of 2,000 kcal corresponds to about 8,368 kJ or 2.32 kWh of food energy. The human body is not an efficient engine, though – only a fraction of the energy consumed is converted into usable work.

In engineering and physics, you encounter various forms of energy: kinetic energy (motion), potential energy (position), thermal energy (heat) and chemical energy. All these forms can be converted into one another and are measured in the same units. Thermal energy is often given in joules or kWh – a litre of heating oil contains about 10 kWh of calorific value. The energy content of fuels is also frequently given in megajoules per kilogram (MJ/kg): petrol has about 43 MJ/kg, diesel about 45 MJ/kg, hydrogen about 120 MJ/kg.

It is important to distinguish between energy and power: power (in watts) is energy per unit of time. 1 watt = 1 joule per second. A 100-watt light bulb consumes 100 Wh = 0.1 kWh = 360,000 J in one hour. With our energy converter, you can quickly switch between all common energy units – whether for heating bills, nutrition planning or physics calculations.