Common Energy Conversions
About Energy Conversion
Convert between different units of energy including joules, calories, kilowatt-hours, BTU, and more. Essential for physics calculations, engineering projects, and energy efficiency analysis.
Frequently Asked Questions
What is the difference between energy and power?
Energy is the capacity to do work (measured in joules, calories, kWh), while power is the rate of energy transfer (measured in watts). Think of energy as the total amount of water in a tank, and power as the flow rate.
How do I convert between calories and joules?
1 calorie = 4.184 joules. Calories are commonly used for food energy, while joules are the SI unit for energy. Nutritional "Calories" (capital C) are actually kilocalories, equal to 1,000 calories or 4,184 joules.
What does kWh mean on my electricity bill?
kWh (kilowatt-hour) measures electrical energy consumption. It's the amount of energy used by a 1,000-watt appliance running for one hour. Your electricity bill charges per kWh consumed.
How much energy is in different fuels?
Energy density varies greatly: gasoline has about 34 MJ/L, natural gas 37 MJ/m³, and lithium-ion batteries 0.5-1 MJ/L. This explains why gasoline is preferred for vehicles despite environmental concerns.
What is BTU and when is it used?
BTU (British Thermal Unit) is the energy needed to heat one pound of water by one degree Fahrenheit. It's commonly used for heating/cooling systems, natural gas, and energy content of fuels in the US.
How do renewable energy sources compare?
Solar panels convert about 15-20% of sunlight to electricity, wind turbines capture 35-45% of wind energy, and hydroelectric plants achieve 80-90% efficiency. Energy storage and grid integration are key challenges.