The most common fuels used for water heating are gas and electricity.
- Electric water heaters that can heat water at any time of day are by far the most expensive option. Off-peak electric (which heat only when tariffs are lower) and gas systems have similar costs, depending on the tariffs you have to pay.
- Natural gas produces much less of the greenhouse gas carbon dioxide (CO2) than electricity to heat the same amount of water. But it’s not available everywhere.