Should Your Water Heater Be On Pilot Or On?

You walk past the water heater in the basement and notice the control knob. It has three positions: Off, Pilot, and On. You spin it to On before a shower, then wonder if leaving it on Pilot all day wastes gas. Most homeowners just set it once and forget it, never thinking about the difference.

This article gets into the specifics. You will know exactly when to use Pilot versus On, how much gas each mode burns, and what happens to the heater itself over time. I will also cover the one scenario where you should turn the whole thing Off. No generic advice here — just numbers and real trade-offs.

If you own an electric water heater, this topic still applies indirectly. Electric heaters don’t have a pilot flame, but they do have thermostats that control when the elements fire. Replacing a worn thermostat can restore performance. The NISHCON EWH-00 kit (ASIN B0DYJMKFNK) includes an upper and lower thermostat with an overheat safety switch. It fits most dual-element electric heaters from brands like A.O. Smith, Rheem, and Bradford White. That kit is worth a look if your electric unit cycles too often or runs cold.

What Pilot and On Actually Do

Let’s define the terms. On a gas water heater, Pilot means only the pilot flame stays lit. The main burner does not fire until the thermostat calls for heat. On means the main burner can fire whenever the water temperature drops below the setpoint. The control valve allows gas to flow to the pilot at all times, but only sends gas to the main burner when the thermostat opens.

In Pilot mode, you still have a tiny flame burning 24/7. That flame consumes gas — roughly 600 to 900 BTU per hour depending on the model. That translates to about 14,400 to 21,600 BTU per day just to keep the pilot lit. Most modern water heaters use around 40,000 BTU per hour of burner operation. So a pilot alone burns about 5% of a full hour’s burner output every day.

In On mode, the pilot stays lit AND the main burner fires as needed. The main burner operates in cycles. A typical family of four uses a 40-gallon tank set at 120°F. That burner might fire two to four times per day for 20 to 30 minutes each time. Total gas consumption is the pilot plus the burner cycles.

The knob you turn is a mechanical gas valve. Turning it to Pilot shuts off gas to the main burner but keeps the pilot line open. That’s a deliberate safety feature — you cannot accidentally turn the main burner on without the pilot lit.

When You Should Use Each Mode

Use Pilot mode when you are away for a weekend or longer

If you leave for a few days, turning the knob to Pilot keeps the pilot flame alive. That means you don’t have to relight it when you return. Relighting a pilot is not hard, but if you have a sealed combustion chamber or an electronic ignition, it can require a specific sequence. Some people mess it up. Pilot mode avoids that hassle.

The downside: you still pay for the pilot gas. A single-pilot flame costs about $3 to $5 per month at average US gas rates. Over a week away, that’s maybe $1 in wasted gas. Not much, but not zero.

If you go for a month, say a winter trip, Pilot mode is still fine as long as you have freeze protection. The tank holds 40 gallons of water. In freezing weather, that water can freeze and burst the tank if the pilot goes out and the house heat fails. I would keep the pilot lit in winter and raise the thermostat to 55°F in the house. Some people turn the water heater Off entirely and drain it. That is the safest approach for long absences, but it is more work.

Use On mode for normal daily living

There is no reason to switch between Pilot and On day to day. Leave it on On unless you are leaving for more than a day. The only exception: an older water heater that has a standing pilot that seems to blow out in windy weather. Then you might switch it to On only when you need hot water and turn it to Pilot when you don’t. That is a workaround for a failing unit, not best practice.

Some people think turning the knob to Pilot at night saves gas. A typical gas water heater loses 0.5 to 1°F per hour through insulation. A 40-gallon tank at 120°F will drop maybe 10°F overnight. In the morning, the burner runs for 15 minutes to bring it back up. The gas used for that recovery is about the same as keeping the tank at temperature all night. The difference is negligible. So don’t bother switching at night.

Turn the knob to Off and shut off the gas supply for extended absences

If you leave for more than 10 days, especially in mild weather, consider turning the water heater Off completely. Shut off the gas valve and also turn off the water supply to the heater. Draining the tank is optional but recommended if you live in a freezing climate. This saves the pilot gas entirely. When you return, you relight the pilot and wait for the tank to heat up. That takes maybe two hours.

Many homeowners worry about forgetting to relight the pilot and then running the main burner without a flame. That cannot happen — the gas valve won’t open the main burner unless the thermocouple senses a pilot flame. So it is safe.

How Pilot vs. On Affects Lifespan and Safety

Leaving the pilot on constantly does wear the thermocouple and control valve over time. A thermocouple is a thin copper wire that sits in the pilot flame. It generates a small voltage that keeps the gas valve open. After 10 to 15 years, thermocouples degrade and the pilot goes out repeatedly. That’s a $15 part to replace. Frequent on-off cycles also stress the gas valve, but that is rare.

Switching between Pilot and On every day puts mechanical wear on the knob and the internal valve stem. This is not a big concern — the knob is designed to be turned thousands of times. But I have seen old valves develop gas leaks around the stem after years of daily twisting. So don’t fidget with it.

Safety-wise, the pilot mode is no less safe than On. The pilot flame is enclosed. If the flame goes out, the thermocouple cools and shuts off the gas supply. That is a proven failsafe. The only danger of leaving a water heater on Pilot is if you have a gas leak elsewhere in the house. Then the pilot could ignite the gas. That is extremely rare.

For electric water heaters, there is no pilot. The control is a thermostat that cycles the elements. If your electric heater is taking too long to recover or runs out of hot water quickly, the thermostat might be failing. The NISHCON EWH-00 kit gives you both upper and lower thermostats with a safety cutoff. It’s an easy swap if you follow the wiring diagram.

Table: Pilot vs. On at a Glance

Mode	Gas Consumption (per day)	Lifespan Impact	Best for	Safety Note
Pilot Only	~15,000 BTU	Slow wear on thermocouple	Short trips (2–10 days)	Thermocouple shuts gas if flame goes out
On (Normal)	~30,000–60,000 BTU	Normal cycling wear	Daily use	Standard operation, no extra risk
Off (Gas Valve Closed)	0 BTU	None	Long absences (10+ days) or freezing risk	Must relight pilot; no gas leak while idle

Numbers vary by tank size, set temperature, and insulation. The table is a representative average for a 40-gallon gas water heater set to 120°F.

Frequently Asked Questions

Will leaving the pilot on waste a lot of gas?

It costs about $3 to $5 per month in the US. That is the gas that keeps the pilot burning 24/7. For a family that lives in the house year-round, that is a minor expense. If you go away for a week, you save around $1 by turning the pilot off. The bigger waste is not the pilot — it’s the heat lost through the tank walls. That is why newer tanks have better insulation.

Is it safe to turn off the pilot when I go on vacation?

Yes, as long as you follow the proper procedure. Turn the control knob to Off. Then shut off the manual gas valve near the water heater if one exists. This isolates the heater from the gas line. When you return, turn the gas valve back on, set the knob to Pilot, hold down the red button until the pilot lights, then release after 30 seconds. Finally set the knob to On. That’s all.

What if my pilot light keeps going out?

A pilot that repeatedly goes out is usually a dirty pilot orifice, a weak thermocouple, or a draft blowing out the flame. Clean the small hole with a needle. Replace the thermocouple if it’s worn. Make sure there is no air leak from the jacket or combustion chamber. If you need guidance, check this article about when a pilot light goes out for a deeper diagnosis.

Can I switch my water heater between Pilot and On every day to save gas?

You can, but you will save maybe $1 per month. The mechanical wear on the gas valve is minor. The inconvenience of waiting for hot water in the morning might not be worth it. Most manufacturers do not recommend daily switching. If you want to save gas, insulate the tank and the first three feet of hot water pipe. That gives a better return.

Does an electric water heater have a pilot mode?

No. Electric water heaters have thermostats that turn the heating elements on and off. There is no continuous flame. The question “Should Your Water Heater Be On Pilot or On?” applies only to gas models. If you own an electric unit, the equivalent decision is what temperature to set and whether to use a timer. If your electric heater is old and the thermostat drifts, a replacement kit like the NISHCON EWH-00 can restore proper cycling.

Things to Remember

• Leave the water heater in On mode for daily use. Switching to Pilot at night saves almost nothing.
• Use Pilot mode when you leave for 2 to 10 days. It keeps the pilot lit so you do not have to relight it.
• Turn the gas valve to Off and shut off the manual gas valve if you leave for more than 10 days. Drain the tank if freezing is possible.
• Never turn a gas water heater to On if the pilot is not lit. The safety valve prevents the main burner from firing, but always verify the pilot flame before turning to On.
• A thermostat that fails on an electric heater will cause cold showers or dangerously high temperatures. The NISHCON EWH-00 kit is a dependable replacement for most dual-element models.
• If your pilot goes out repeatedly, fix it rather than switching modes constantly. A dirty pilot orifice or a dead thermocouple are cheap repairs.
• Follow the manufacturer’s instructions every time you relight the pilot. Every brand has a slightly different sequence. For a step-by-step, see how to restart your gas water heater safely.