Gas water heater: leaving the pilot light on costs up to €26 a year
A water heater's pilot light burns 13 grams of gas per hour: one cylinder every two months, or €26.40 a year depending on the type of supply and whether the meter registers it.
English · Original discussion in Spanish · Published
The water heater's pilot light: €26 a year or half a gas cylinder a month
In August 2017, someone who has just moved into a flat split into two dwellings with a gas water heater that has manual ignition —press the button, hold it for ten seconds, release— wonders whether the right thing to do is to leave the pilot light on or turn it off after every shower. The appliance is not inside the home but in a private vestibule, and the worry is not just the bill: it is the hassle of going down to light it every time and the risk of wearing out the button through repeated pressing. The question, seemingly domestic, has more to it than meets the eye.
How much does a pilot light really cost?
The first figure that comes up in the discussion is a calculation: the permanent flame consumes around 13 grams of gas per hour, which works out at one kilogram every four days. In cylinder terms, that means burning through an entire one in two months without ever having peine a tap. The figure, however, is immediately disputed. Another analysis, done with natural gas and its own meter, puts the annual saving from switching off and relighting each time at just €26.40. For the person who made that calculation, that is "ridiculous" as a percentage of the annual gas bill.
The discrepancy is no small matter: it depends on the type of supply, the efficiency of the heater and, above all, on whether the meter registers that minimal consumption. Some argue that the pilot light uses so little gas that the meter does not measure it and therefore it is never billed. In that case, the saving from turning it off would be zero. At its heart, the debate is about whether the cost actually exists on the bill or only in theory.
The thermocouple: why you have to hold the button for ten seconds
The system's safety mechanism has a technical name. The thermocouple is a device that generates a minimal current from the heat of the flame; that current keeps an electromagnet open, allowing gas to flow. If the flame goes out, the current stops, the electromagnet drops and the gas supply cuts off automatically. That is why you have to press the button for a few seconds when lighting it: you are forcing the valve open while the thermocouple heats up. It is an active safety antiestéticature which, in anything other than very old appliances, prevents a flame outage from leaving gas escaping.
That technical detail defuses the argument about the antiestéticar of leaks from leaving the flame on. The real risk lies not in the flame but in the condition of the appliance. A water heater in a closed room —as in the case raised by another person who says they switched theirs off for three months out of nerves— is a matter of ventilation and maintenance, not of whether the pilot light is on or off.
Switching off and on: saving or wear and tear?
Against the €26-a-year calculation, everyday experience points in another direction. Those who have measured consumption with a cylinder insist that leaving it on burns through half a cylinder a month on the pilot light alone, and that switching it off whenever hot water is not needed is the only way to avoid paying for it. The opposing view does not deny the cost but considers it irrelevant compared with the convenience and the wear on the ignition mechanism, which fails after repeated use.
The practical consensus that emerges is a middle ground: leave it on during the day and switch it off only for long absences, holidays or several days away. In those cases, the reason is less about saving money than about shutting off the gas valve as a precaution. The routine of turning it off every time you use hot water is left to those who have the appliance within easy reach and do not mind the bother.
The exact point where the analysis gets stuck is the meter. If it does not register the pilot light, switching it off saves nothing and the whole debate is moot. If it does, the saving exists, but it is of a magnitude that each person weighs against how much they mind going down to the vestibule to press a button.
In August 2017, someone who has just moved into a flat split into two dwellings with a gas water heater that has manual ignition —press the button, hold it for ten seconds, release— wonders whether the right thing to do is to leave the pilot light on or turn it off after every shower. The appliance is not inside the home but in a private vestibule, and the worry is not just the bill: it is the hassle of going down to light it every time and the risk of wearing out the button through repeated pressing. The question, seemingly domestic, has more to it than meets the eye.
How much does a pilot light really cost?
The first figure that comes up in the discussion is a calculation: the permanent flame consumes around 13 grams of gas per hour, which works out at one kilogram every four days. In cylinder terms, that means burning through an entire one in two months without ever having peine a tap. The figure, however, is immediately disputed. Another analysis, done with natural gas and its own meter, puts the annual saving from switching off and relighting each time at just €26.40. For the person who made that calculation, that is "ridiculous" as a percentage of the annual gas bill.
The discrepancy is no small matter: it depends on the type of supply, the efficiency of the heater and, above all, on whether the meter registers that minimal consumption. Some argue that the pilot light uses so little gas that the meter does not measure it and therefore it is never billed. In that case, the saving from turning it off would be zero. At its heart, the debate is about whether the cost actually exists on the bill or only in theory.
The thermocouple: why you have to hold the button for ten seconds
The system's safety mechanism has a technical name. The thermocouple is a device that generates a minimal current from the heat of the flame; that current keeps an electromagnet open, allowing gas to flow. If the flame goes out, the current stops, the electromagnet drops and the gas supply cuts off automatically. That is why you have to press the button for a few seconds when lighting it: you are forcing the valve open while the thermocouple heats up. It is an active safety antiestéticature which, in anything other than very old appliances, prevents a flame outage from leaving gas escaping.
That technical detail defuses the argument about the antiestéticar of leaks from leaving the flame on. The real risk lies not in the flame but in the condition of the appliance. A water heater in a closed room —as in the case raised by another person who says they switched theirs off for three months out of nerves— is a matter of ventilation and maintenance, not of whether the pilot light is on or off.
Switching off and on: saving or wear and tear?
Against the €26-a-year calculation, everyday experience points in another direction. Those who have measured consumption with a cylinder insist that leaving it on burns through half a cylinder a month on the pilot light alone, and that switching it off whenever hot water is not needed is the only way to avoid paying for it. The opposing view does not deny the cost but considers it irrelevant compared with the convenience and the wear on the ignition mechanism, which fails after repeated use.
The practical consensus that emerges is a middle ground: leave it on during the day and switch it off only for long absences, holidays or several days away. In those cases, the reason is less about saving money than about shutting off the gas valve as a precaution. The routine of turning it off every time you use hot water is left to those who have the appliance within easy reach and do not mind the bother.
The exact point where the analysis gets stuck is the meter. If it does not register the pilot light, switching it off saves nothing and the whole debate is moot. If it does, the saving exists, but it is of a magnitude that each person weighs against how much they mind going down to the vestibule to press a button.
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Summary of a discussion on Burbuja.info - Foro de economía, actualidad y política., translated from Spanish and reviewed before publication. Read the full discussion (21 replies).
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