Dossier ENGIE
How to Check Whether Your Water Heater Is Running During Off-Peak Hours
Like many households in France, have you chosen an off-peak / peak-hour contactor (“contacteur heures creuses / heures pleines”) to reduce your energy bills? If so, it is important to make sure it is working properly. Here is how to check it!
Would you like to save energy during off-peak hours, but are unsure whether your water heater is working properly during these periods? To make sure your water heater switches on only during off-peak hours and that your contactor is set to the correct position, follow the guide below!
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Preliminary steps to check that your water heater is running during off-peak hours
After carefully assessing your electricity needs, you decided to subscribe to a peak-hour / off-peak electricity contract (“heures pleines / heures creuses”). But are you sure that your hot water tank is operating correctly during off-peak hours? Here are the steps to follow to make sure your water heater works properly during these lower-tariff periods.
1. Make sure you have subscribed to a peak-hour / off-peak electricity contract
First, check the pricing option on your electricity contract. Your contract should mention two different electricity rates depending on the time of day. Does your contract only include one rate? If so, you are on a standard flat-rate tariff. In that case, limiting your water heater usage to off-peak hours will not provide any benefit. Contact your energy supplier to change your contract if needed.
To view your bill and check which offer you subscribed to, log into your customer account or contact your energy supplier directly.
2. Check that there is a contactor installed on your electrical panel
Second step: check that a contactor is installed and verify its position. If present, it must be set to the AUTO position in order to benefit from the peak-hour / off-peak system. It is a small device installed directly on your electrical panel. It looks similar to a circuit breaker, except that it has three positions: I, AUTO and O.
Why is the contactor essential for using the peak-hour / off-peak system?
When your home enters off-peak hours, the energy supplier sends an electrical signal to the contactor, activating both the contactor and your water heater. Once off-peak hours end, the electricity meter switches the contactor off again, cutting power to the water heater.
So if you cannot find a contactor on your electrical panel, it is perfectly normal that your water heater cannot operate automatically according to peak and off-peak hours!
What should you do if there is no contactor?
Don’t worry — it is entirely possible to buy and install one. Here is how.
Where can you buy a contactor and how much does it cost?
You can easily find one in most DIY or home improvement stores starting from around €20, although prices can increase quickly depending on the model and power rating.
How do I install my contactor?
Once you have purchased your contactor, it’sit is time to install it on your electrical panel.
Are you comfortable with DIY work and electrical connections? If so, you can install the contactor yourself. Installation is relatively quick and can generally be completed in less than two hours. Otherwise, call a qualified electrician.
If you decide to install the contactor yourself, make sure you switch off your main circuit breaker before starting and use proper protective equipment to avoid electrical hazards. Insulated gloves and safety glasses are essential for your protection.
Once installation is complete, simply switch the circuit breaker back on and set your contactor to the AUTO position.
What do the different contactor positions mean?
Automatic mode powers the water heater only during off-peak hours. Your contactor has three possible positions:
Position I: your water heater is in “forced operation” mode (“marche forcée”), meaning it receives electricity continuously, both during peak and off-peak hours. This position is useful if you need additional hot water during peak hours.
AUTO position: as explained above, this mode ensures that your hot water tank only operates during off-peak hours, while its electricity supply is cut off for the rest of the day. This is the correct position if you want to benefit fully from your electricity plan.
Position 0: this position switches your appliance off completely if you are away for a long period, especially during holidays. However, if you are leaving only for a short time, switching off your water heater is generally not worthwhile. When hot water is not being used, very little energy is required to maintain its temperature. Allowing the tank to cool down for one or two nights will actually require more energy later to heat the water back up again. In general, it only becomes worthwhile to switch off your hot water tank after around 3 days of absence.
What should I do if I experience a problem with my water heater during off-peak hours?
Is your contactor correctly set to AUTO and does your electricity subscription clearly include the dual-tariff option? Yet your water heater consumption still does not seem to follow off-peak hours? Contact an electrician so they can check that the contactor and the water heater’s power supply are functioning properly.
Why does hot water take time to arrive?
Is your water cold when you turn on the hot water tap? Don’t worry — this is completely normal and does not mean that your water heater is malfunctioning. The residual water sitting inside the pipes is cold. As a result, you first need to “flush” the cold water from the system (let the water run briefly) before hot water reaches the tap. The greater the distance between the water heater and the outlet, the longer you will need to wait before enjoying your hot shower.
Can I use my water heater during peak hours if I subscribed to off-peak hours?
Do you occasionally need hot water during peak hours? Even if you subscribed to a special peak-hour / off-peak electricity contract, this is entirely possible. You simply need to switch your contactor to position I, which activates forced operation mode for your water heater regardless of the time of day.
However, it is important to remember that electricity consumed during peak hours is billed at a higher rate than during off-peak hours. This is something to consider when reviewing your energy bill. If you regularly use your water heater during peak hours, it may be more cost-effective to switch to a standard base-rate electricity contract instead.
Please note that if your hot water tank was correctly sized during installation, whether it operates during peak or off-peak hours will have no impact on water temperature. Since hot water tanks are well insulated, water heated overnight remains hot throughout the day and available in the evening. Under normal use conditions, you should therefore not run out of hot water, regardless of when you shower.
What are the advantages of an off-peak electricity plan?
Choosing an energy contract that includes both peak and off-peak hours offers several advantages:
You reduce your energy costs on a daily basis;
You benefit from a reduced electricity rate per kWh for 8 hours each day;
This option is generally advantageous for larger households;
If you have a Linky™ smart meter and are an ENGIE customer, you can easily monitor your consumption using our dedicated app.
However, this option is not suitable for everyone and may also present some disadvantages depending on your lifestyle:
The subscription cost is higher than for a standard electricity plan;
If you use electrical appliances during peak hours, the electricity rate is also higher;
If you rarely use electrical appliances, this option may not be financially worthwhile.
What if you switched to the Week-end option?
To better adapt to your needs, ENGIE created the Week-end option. Thanks to this offer, you benefit from a 30% discount on the price per kWh throughout the weekend and on public holidays.
Running your water heater during off-peak hours: key points to remember
To benefit from lower electricity rates for hot water usage during off-peak hours, installing a contactor is essential. This device is installed directly on the electrical panel and has three positions: I, AUTO and 0. The AUTO position is the one required for your appliances to operate during off-peak hours.
To verify that your water heater switches on during off-peak hours, make sure your contactor is correctly set to AUTO and that you have subscribed to an energy contract including the peak-hour / off-peak-hour option.
Choosing an electricity contract with off-peak hours allows you to benefit from preferential electricity rates and reduce your energy costs every day. However, before subscribing to this type of offer, make sure that your lifestyle and the off-peak time slots available in your local area truly match your needs.
Off-peak hours vary from one municipality in France to another. To find out exactly which off-peak hours apply to your home, contact your energy supplier or refer to your electricity bill.
Using hot water during peak hours remains possible. You simply need to switch your contactor to position I. However, keep in mind that your electricity consumption costs will increase during these periods because the price per kWh is higher.
Choosing an electricity subscription that includes off-peak hours offers several advantages. In particular, you benefit from preferential electricity rates during off-peak periods while reducing your overall energy consumption.
What water heater capacity should I choose?
The size of the water heater mainly depends on the number of people in the household. For one person living alone, a water heater with a 75 to 150 L tank is generally sufficient. For a family of four, however, it is recommended to choose a water heater with a capacity between 200 and 300 L.
Do I need to change my electricity meter if I want to switch to a peak-hour / off-peak-hour plan?
If you already have a Linky™ meter, there is no need to replace your electricity meter. You simply need to contact your energy supplier, and an advisor will inform ENEDIS so that your meter can be remotely programmed. With a Linky™ smart meter, this change can usually be carried out remotely.
If your meter is not compatible with adding a contactor, your equipment will need to be replaced. This service generally costs between €40 and €60. If you do not yet have a Linky™ communicating meter, replacing the equipment may also be necessary depending on your situation.
How much electricity does a water heater consume?
A water heater is estimated to consume around 800 kWh of electricity per person each year on average. Alongside heating, it's one of the main sources of energy consumption in a household.
