A gas water heater uses the heat from burning a fuel (usually natural gas) to heat water, while an electric water heater uses electric resistance coils. Gas water heaters are less energy efficient than electric heaters, but the cost of electricity itself makes the running costs of an electric heater higher. Gas water heaters also have a much faster recovery rate, which makes them a convenient option for larger families.
In the United States, about 60% of homes use gas-fired water heaters, and 40% use electric.
A gas heater can heat a 50-gallon tank in about one hour. Its recovery rate (i.e. time taken to reheat a tank of water after use) is much faster than that of an electric heater. Another advantage of traditional gas water heaters is that they’ll still work in the event of a power outage. For families of four or more people, a gas heater is usually a better choice over electric, as an electric heater is likely to have trouble keeping up with the hot water demands of a larger family.
The main disadvantage of an electric water heater is the relatively slow recovery rate. A typical 50 gallon tank will usually require several hours to recover. Also, electric units are vulnerable to power outages, and will not work in the event of one.
This video explains the differences between a gas water heater and an electric water heater:
Conventional gas storage units are relatively inefficient because of the heat loss from exhaust gases and walls of the storage tank. Water is kept hot at all times, and while this is a good convenience, it means energy is constantly used/lost. However, modern units are increasingly efficient, and top-of-the-line condensing units are very energy efficient. Two inches of foam insulating around the storage tank can significantly increase efficiency. See the table below for specific numbers.
Electric heaters are much more energy efficient than gas units, but the savings in actual energy consumption are mitigated by the higher costs of electricity as opposed to gas. Electric heat pump units are vastly more efficient than any other option, however, they remain relatively rare and have high installation costs.
- In North American households, the most common type of water heaters is the storage tank, which can store 20-100 gallons of water hot and ready to use at any time. This system provides a large amount of hot water, but requires recovery time after the tank has been used.
- Tankless heating, which traditionally uses electric coils, but has recently become more popular for gas-fired units, heats water on demand, thereby providing a limitless supply of hot water. These units are more expensive than traditional storage water heaters, and restrict the flow of water to keep it hot.
- The high-efficiency option for gas heaters is condensing boilers. These units use heat from the exhaust gases to preheat cold water coming into the tank. This can achieve a 20% increase in efficiency over traditional gas storage units. However, the initial cost of condensing boilers is about twice that of a traditional unit.
- A relatively new option in electric heating is the heat pump device. These units extract heat from the surrounding air to heat water. Electric resistance elements are still present to provide backup heating. Heat pump units are by far the most efficient domestic water heaters, but they are much more expensive than other options.
Cost and Lifespan
While traditional gas and electric storage units are similar in initial purchase price, electricity costs more to use than gas, that means over time, electric units are more expensive to operate. Installation of an electric water heater can be made more expensive by the requirement for a 220 volt outlet, and the wiring for this in an electrical panel. Electric water heaters may have a slightly longer lifespan than gas units, but this largely depends on local water quality and owner maintenance.
For consumers, gas is almost always a cheaper option than electricity, and this simple fact has been enough for many homeowners to choose gas water heaters. If a gas line is already available in a house, it is a much cheaper option. Switching over from electric to gas can be expensive, because it may require installation of a gas line and venting for exhaust heat. Gas heaters can have a slightly shorter lifespan, but the difference is not significant (12 instead of 13 years, for example).
Pricing and Purchase