The energy efficiency of electric boilers depends on how the loss of energy is measured, but Bryan's electrical heaters have higher efficiency ratings than gas ones. Energy losses at power plants, however, can make electricity less efficient than gas.
Electrical boilers use nearly all of the electricity they draw to heat water, making them the most efficient designs according to some calculations. Much of this efficiency is due to their electrical resistance technology, which wastes little energy. In addition, boilers that use fuel almost always have vents, which transfer a bit of the heat they generate outside.
However, power plants that use fossil fuels have to convert heat to electricity, which comes at the cost of efficiency. Energy is also lost as electricity is sent through power lines, and power plants sometimes generate more electricity than is needed to deal with spikes. As a result, gas-powered boilers often use natural gas more efficiently than electrical boilers powered by a natural gas power plant.
Operating costs tend to favor gas-powered units, but varying natural gas and coal prices can make savings difficult to calculate. Gas units are typically recommended for those with access to a gas line, while electrical units may be a better option for those who would need to use bottled fuel.