When the power goes out, it's useful to have some kind of backup for your appliances. If you have a gas water heater, you may assume that you'll still get hot water even during a power outage, but this isn't necessarily the case. Your water heater may or may not require electricity depending on its ignition system.
Some gas water heaters use electricity to power their ignition system, but some do not. If maintaining hot water during a potential power outage is a priority for you, be sure to install a hot water heater with a standing pilot system rather than an electronic system.
Types of Fuel Ignition Systems
All gas appliances, including gas water heaters, need an ignition system to start fuel combustion. Every gas water heater has a gas control valve that includes a valve, thermostat and some type of ignition system. The valve controls the release of gas when the thermostat reaches a certain temperature.
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Before the 1980s or so, all gas appliances, including water heaters, used standing pilot ignition systems, but electronic ignition systems are more common now, although you can still find the standing pilot types if you prefer them. Among the electronic ignition systems, there are two primary types: intermittent pilot ignition and hot surface ignition (HSI).
Many consumers prefer water heaters that use the HSI system because they're more economical to run since they don't require a continuous pilot light to function. Further, these units don't contribute to a room's heat during the summer months when even the smallest heat source can make an uncomfortable difference in an already too-warm house.
But if you're concerned about power outages in your area, you may want to further research the pros and cons of electronic ignition systems and standing pilot lights.
Standing Pilot Systems Don't Need Electricity
Most people are familiar with the visible pilot light in the "standing pilot" ignition system. This small light is used to light the main gas burner, and for proper operation, this pilot light must be continually on. Standing pilot systems use piezo igniters that generate electric sparks and ignite the pilot.
Standard piezo igniters incorporate a push button — everyone probably has the experience of turning on the pilot switch and repeatedly pressing a button to start a pilot light. Since you yourself are providing the energy to light the pilot, no electricity is required for this type of ignition.
Electronic Ignition Systems Do Need Electricity
Electronic ignition systems were developed to be more economical and environmentally friendly than those that require a continuous pilot because the pilot light doesn't need to be, well, continuous.
To reiterate, there are two main types of electronic ignition systems: intermittent pilot and hot surface ignition. The intermittent pilot, similar to the standing pilot type, uses a small, gas-powered flame to ignite the gas burners in your water heater, but this pilot burns only until the burners ignite. It was initially developed as an improvement to the pilot ignition system because it doesn't require a match. A water heater with an HSI system uses resistance elements made of either silicon carbide or silicon nitride. These require a jolt of electricity to heat them until they glow orange or red, thus igniting the burners.
All electronic ignition systems do require electricity. If your system doesn't have a continuous pilot, it's of the electronic type.