When your water heater fails, and in Aiken's climate where water heaters work year-round, they typically last 8 to 12 years, the replacement decision often comes down to electric versus gas. Both types have distinct advantages and disadvantages, and the right choice depends on your home's existing infrastructure, your energy costs, your hot water usage patterns, and your long-term plans.
As electricians, we obviously work on the electrical side of this equation, but we believe in giving our customers the full picture so they can make the best decision. Here is a comprehensive comparison of electric and gas water heaters, with a focus on the electrical requirements, installation differences, and operating costs that matter most to Aiken homeowners.
How Electric Water Heaters Work
An electric water heater uses one or two immersion heating elements to heat the water inside the tank. Each element is a resistance heater, similar in principle to the heating element in an electric oven, that is submerged directly in the water. When the water temperature drops below the thermostat setting, the elements turn on and heat the water until it reaches the target temperature.
Most residential electric water heaters have two elements: an upper element and a lower element. They operate alternately, not simultaneously, in what is called a non-simultaneous or flip-flop configuration. The upper element heats the top of the tank first (providing hot water for immediate use), and once the upper section reaches temperature, the lower element takes over to heat the rest of the tank. This design reduces the electrical demand at any given moment while still providing a full tank of hot water.
A standard residential electric tank water heater in Aiken is typically a 40-gallon or 50-gallon unit with two 4,500-watt elements. Each element draws approximately 18.75 amps at 240 volts. Because only one element operates at a time, the maximum draw is 18.75 amps, which requires a dedicated 30-amp, 240-volt circuit with 10-gauge copper wire.
How Gas Water Heaters Work
A gas water heater uses a burner at the bottom of the tank to heat the water. Natural gas or propane is ignited by a pilot light or electronic ignition, and the flame heats the bottom of the tank. Hot combustion gases rise through a flue tube that runs vertically through the center of the tank, transferring additional heat to the water as they travel upward and exit through the vent pipe.
Gas water heaters still require some electricity, but significantly less than electric models. A gas water heater with a standing pilot light requires no electricity at all; the pilot light runs continuously on gas, and the thermostat is a mechanical device that does not need power. Modern gas water heaters with electronic ignition systems require a 120-volt electrical connection for the igniter and control board, typically drawing less than 5 amps. This can be a standard 120-volt outlet near the water heater.
Electrical Requirements Comparison
The electrical infrastructure needed for each type is one of the most important factors in the decision, because modifying your home's electrical system adds cost to the installation.
Electric water heater electrical requirements: A dedicated 30-amp, 240-volt circuit with 10-gauge copper wire and a 30-amp double-pole breaker in the panel. The circuit terminates at a junction box on or near the water heater, where it connects to the heater's internal wiring through a flexible conduit whip. A disconnect switch within sight of the water heater is also required by code. If your Aiken home already has an electric water heater, this circuit is already in place. If you are switching from gas to electric, this circuit must be installed new.
Gas water heater electrical requirements: For models with electronic ignition, a 120-volt outlet near the water heater location. Many gas water heaters with standing pilot lights require no electrical connection at all. If your home currently has a gas water heater with no electrical connection and you want to install a new model with electronic ignition, adding a 120-volt outlet is a minor electrical task.
Tankless electric water heater electrical requirements: This is where the electrical demands become significant. A whole-house tankless electric water heater requires substantially more electrical capacity than a tank model. A typical unit needs two or three 40-amp or 50-amp, 240-volt circuits, requiring 6-gauge or 8-gauge copper wire. The total connected load can be 27,000 to 36,000 watts (112 to 150 amps at 240 volts). Most Aiken homes with 200-amp service can support this load, but homes with 100-amp or 150-amp service may need a panel upgrade.
Efficiency Comparison
Energy efficiency is measured by the Uniform Energy Factor (UEF), which represents the ratio of useful energy output to total energy input. A higher UEF means more of the energy you pay for actually heats your water.
Electric tank water heaters: UEF of 0.90 to 0.95 for standard models. Electric water heaters are inherently efficient because the heating elements are immersed directly in the water, so virtually all the electrical energy is converted to heat in the water. There are no combustion losses and no heat escaping up a flue.
Gas tank water heaters: UEF of 0.58 to 0.70 for standard models, and 0.80 to 0.90 for high-efficiency condensing models. Gas water heaters lose efficiency because some heat energy goes up the flue with the exhaust gases, and some heat is lost through the combustion process itself. Condensing gas water heaters recapture some of this lost heat, achieving significantly higher efficiency.
Heat pump water heaters (hybrid electric): UEF of 2.0 to 4.0. These units use a heat pump to extract heat from the surrounding air and transfer it to the water, similar to how an air conditioner works in reverse. They use 2 to 3 times less electricity than a standard electric water heater, making them the most efficient option available. However, they work best in unconditioned spaces like garages and basements where they have access to warm ambient air, and they do not perform as well in very cold environments. In Aiken's mild climate, heat pump water heaters can perform well year-round.
Operating Cost Comparison
The operating cost of a water heater depends on the fuel cost in your area, the efficiency of the unit, and your household's hot water usage. Here is a comparison based on typical Aiken energy costs.
Aiken's average electricity rate is approximately $0.13 per kWh. Natural gas costs approximately $1.20 per therm (100,000 BTU). Based on a household using approximately 64 gallons of hot water per day (the DOE standard test condition), here are the approximate annual operating costs.
Standard electric tank (UEF 0.93): Approximately $450 to $550 per year. The electric rate in the Aiken area makes this a moderate operating cost.
Standard gas tank (UEF 0.62): Approximately $300 to $400 per year. Despite the lower efficiency, gas is typically less expensive per unit of heat energy in the Aiken area, resulting in lower operating costs.
High-efficiency gas (UEF 0.85): Approximately $220 to $300 per year. The higher efficiency reduces gas consumption significantly.
Heat pump water heater (UEF 3.0): Approximately $150 to $200 per year. The dramatically higher efficiency makes this the least expensive to operate, despite using electricity.
Over the 10 to 12 year life of a water heater, the operating cost difference between an electric tank and a gas tank is approximately $1,000 to $2,000, favoring gas. However, the heat pump water heater saves $3,000 to $4,000 over the same period compared to a standard electric tank.
Installation Cost Differences
The installation cost depends heavily on whether you are replacing the same type of water heater or switching fuel types.
Replacing electric with electric: This is the simplest installation. The existing circuit, disconnect, and plumbing connections are reused. Installation cost (labor only, not including the water heater) is typically $300 to $600.
Replacing gas with gas: Similarly straightforward if the existing gas line, venting, and connections are in good condition. Installation cost is typically $400 to $700 due to the additional gas connections and venting work.
Switching from gas to electric: This requires installing a new 240-volt, 30-amp circuit from the panel, which adds $300 to $800 to the installation cost depending on the distance and routing. The gas line must also be properly capped.
Switching from electric to gas: This requires running a gas line to the water heater location and installing proper venting, which is typically handled by a plumber or HVAC contractor. The existing electrical circuit can be decommissioned or repurposed.
Panel Capacity Considerations
Before installing or switching to an electric water heater, your electrical panel must have adequate capacity. A standard electric tank water heater requires a 30-amp, 240-volt circuit, which draws approximately 4,500 watts. For a home with a 200-amp panel, this is not typically a concern. For homes with older 100-amp or 150-amp panels, the additional load may push the total demand beyond the panel's capacity, necessitating a panel upgrade.
This is particularly relevant for Aiken homeowners considering a tankless electric water heater, which requires significantly more electrical capacity. A whole-house tankless electric unit can require 100 to 150 amps of dedicated capacity, which is often more than half the total capacity of a 200-amp panel. A load calculation is essential to determine whether your panel can support a tankless electric unit without compromising capacity for your other electrical needs.
Heat pump water heaters offer an interesting middle ground: they provide the benefits of electric operation with a much lower electrical demand than either tank or tankless electric models. Most heat pump water heaters operate on a standard 30-amp, 240-volt circuit, the same as a conventional electric tank.
Which Is Right for Your Home?
The best choice depends on your specific situation. Choose a standard electric tank water heater if your home already has the electrical circuit in place, you do not have a gas line, or you want the simplest and least expensive installation. Choose a gas tank water heater if your home has a gas line and venting in place and you want the lowest operating cost among standard tank models. Choose a heat pump water heater if you have a suitable installation location, you want the lowest operating costs, and you are eligible for federal tax credits and utility rebates. Choose a tankless electric water heater if you have adequate panel capacity, want continuous hot water, and are willing to invest in the required electrical infrastructure.
Unity Power & Light provides electric water heater installation and the associated electrical circuit work for homeowners throughout Aiken, SC and the surrounding CSRA area. We can evaluate your panel capacity, install the required circuits, and coordinate with your plumber to ensure a smooth installation. If you are considering switching from gas to electric, or upgrading to a heat pump or tankless electric unit, we can assess your electrical system and provide a clear plan for the work required.