Why Does My 'Gas' Water Heater Need Electricity?

When I decided to replace my old, rumbling tank water heater, I chose a new tankless model. I specifically picked a natural gas unit because I wanted to save on electricity.

Imagine my confusion when the installer started mapping out where to drill a hole for a new electrical outlet.

“Hold on,” I said. “That’s the gas heater. Why does it need an outlet?”

He smiled and explained something that seems obvious in hindsight, but is the single most common point of confusion for new owners. It’s a great question, and it was even echoed in a customer review I saw: “Uses more electricity than I’d like for a gas water heater.”

Here’s the simple answer: Gas is the fuel for heating, but electricity is the power for thinking.

Think of your new heater like a modern car. Gasoline (natural gas) makes it go, but you still need a battery (electricity) to run the engine computer, the fuel injectors, the headlights, and the radio. Your 30-year-old tank heater was like a 1970s carburetor engine; it worked, but it was dumb, inefficient, and always “on” (that old pilot light).

Your new tankless heater is a smart appliance. When you turn on the tap, it doesn’t just “light.” It boots up.

So, where is that electricity actually going? It runs three critical systems.

1. The Brain and Senses (Control Panel and Sensors)

The most obvious power draw is that “LED Temperature Control Panel” you see on the front. That’s the face of the unit’s onboard computer (ECU).

This computer’s job is to think. It reads data from multiple electronic sensors: * A Flow Sensor detects that you’ve opened the tap and how much water is flowing. * A Temperature Sensor (or two) reads the incoming cold water temperature. * An Exhaust Sensor checks to make sure the vent is clear.

The computer takes all this data and calculates exactly how much gas to release and exactly how fast to run the fan to give you that perfect 120°F (or 49°C) water you requested. This precision is what saves you money, and it all runs on electricity.

2. The Spark (Electronic Ignition)

Your old heater likely had a “pilot light,” a tiny, constantly-burning flame that wasted gas 24/7/365, just waiting for you to need hot water.

Modern heaters are far more efficient. They use an electronic igniter, just like the one in your gas stove or BBQ. When you open the tap, the “brain” sends a signal to this igniter, which creates a high-voltage spark to light the burner. No constant flame, no wasted gas. But… that spark needs electricity.

3. The Lungs (The Powered Blower)

This is the big one. If you look at the specs for a modern unit, especially an outdoor one like the Ranein 8.5 GPM model, you’ll see a feature like “Powerful Blower for Outdoor Safety.”

This is a high-speed fan. It has two jobs:
1. Safety: It actively pushes exhaust fumes (like carbon monoxide) out and away from the unit, preventing dangerous backflow.
2. Efficiency: It sucks in the perfect amount of air to mix with the gas, ensuring a clean, total combustion. This is how it adapts to wind or air pressure.

This blower is a motor. And motors are often the most power-hungry part of the system (outside of the heating itself). This is the “cost” of high-efficiency, high-safety design.

So, Does It Use a Lot of Electricity?

This is the key question. When it’s all added up, how much power are we talking about?

It’s important to separate running power from heating power. * A gas tankless heater might use 50 to 100 watts of running power for its brain, sensors, and fan. * An electric tankless heater uses 18,000 to 28,000 watts of heating power.

The electrical cost of running your gas heater is trivial, probably amounting to just a few dollars per year. It’s a tiny price to pay for the massive gas savings you get from ditching the pilot light and heating on demand.

But it does lead to one critical takeaway: If your power goes out, your modern gas water heater will stop working. It’s a smart device, and smart devices can’t think in the dark.