High Efficiency Water Heaters: A Look at Gas and Solar Heaters

A water heater is a device that uses an energy source to raise the temperature of water. The energy source can be either gas, electric, or solar. The hot water is stored in a tank, then distributed throughout a home and used in sinks, showers, baths and lavatories. Heating domestic water accounts for 15-20 percent of a home’s energy use, and high efficiency water heaters use 10 to 40 percent less energy than standard models, which shows a great potential for lowering utility bills for using high efficiency water heaters. The three main types of water heaters used are storage tank heaters, instantaneous heaters, and solar thermal heaters.

Storage Tank Water Heaters

Storage tank water heaters are the most common type of water heaters. They range in size from 20 to 80 gallons and are fueled by electricity, natural gas, solar heat or oil. Water is heated and stored in an insulated tank and it is available to be used on the demand. Hot water exits from the top of the tank while cold water is heated as it enters the bottom of the tank.

Energy efficient gas-fired storage water heaters are a cost-effective solution in replacing standard efficiency water heaters. Condensing water heaters save substantially more energy than traditional water heaters, with thermal efficiencies of over 90%. A condensing water heater captures heat from the flue gases and uses them to heat the combustion process. An energy efficient storage water heater will typically have better insulation to retain heat inside the tank, an electronic ignition that eliminates the need for a continuous pilot light, better control of flue gases, and a condensing heat exchanger that increases combustion efficiency.

Instantaneous Water Heaters

These water heaters do not have a storage tank, are compact and can be hung on a wall. Instantaneous water heaters are more energy efficient than storage tank water heaters. They will heat water only when it is needed and thus avoid insulation heat loss through a tank’s walls. Instantaneous water heaters can be powered by natural gas or electricity. They are typically used to heat a specific area and do not carry the capacity to heat an entire house.

If you were to heat an entire house, it would be better to buy a storage tank water heating system and use instantaneous water heaters for supplemental heat if needed. To heat specific areas of the house, instantaneous water heaters are better and more energy efficient.

Solar Thermal Water Heaters

Solar water heaters use solar panels to extract the sun’s energy and heat water. They usually use a gas-fired or electric water heater as backup in case there are extended periods without sunlight. Solar water heaters are a great investment because they use a renewable source of energy for a system that demands a high amount of energy such as a home’s water heater.

The initial cost of installing a solar thermal water heater is higher than instantaneous and storage tank water heaters, but the higher cost is worth it for a two reasons:

1. Solar water heaters are eligible for rebates from utility companies and federal tax credits from the government. This means that the initial investment cost will be reduced when the system is purchased and a tax credit will be applied at the end of the year.
2. Depending on weather conditions, a solar system can reduce water heating bills by 90% a year. The energy savings that can offset the installation costs of the system after a few years.

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So Which Water Heater is Better?

It depends on the application. If you just need to heat a single area like a kitchen or the bathrooms upstairs, then an instantaneous water heater is the right choice. They are more energy efficient than traditional water heaters. If you are heating an entire home then a high efficiency, condensing, natural gas water heater is better. If your home is located in a climate where there is a good amount of sunlight during the year then a solar thermal water heater is the way to go.