NASA
Climate Kids: 10 Interesting Things About Energy
Discover 10 very interesting things about energy, including conservation, fossil fuels, daylight savings time, hydropower, wind energy, solar power, greenhouse gases and BTUs (British Thermal Units).
US Energy Information Administration
U.s. Eia Energy Kids: Energy Units Basics
Instructions for converting the physical measurements of different types of fuels, such as gallons or barrels, to British thermal units (Btu), allowing for cross-comparison.