A dome, therefore, will always use less material to cover the same space utilized by a 'square' conventional building. Less material means less cost, or higher quality materials for the same cost, or both. Domes are energy efficient. To illustrate one aspect of the energy efficiency, think about the tanks we have just built. Obviously, the square tank would, because it has less water to remove.
Energy works in a similar way.
The heat in the tanks must radiate through the material. More surface area of material dissipates energy faster than less surface area. Since both tanks used the same amount of material, the spherical tank must radiate longer to remove the heat from its greater volume of water. The tank's energy efficiency is measured by how well it maintains a constant level of energy. Let's imagine that the spherical tank shrunk to the same volume of the cubical tank.