In a connected home, the operation of household appliances is optimized to lower energy consumption, thanks to electricity storage systems -

© Chesky - Shutterstock (via The Conversation)

  • There are systems for saving energy - especially electricity - in individual homes, according to our partner The Conversation.

  • Example with the ECCO software, developed by a research unit at the University of Tours and aimed at understanding the value of the “smart” home to help households reduce their electricity bills.

  • The explanation of this project was written by Sébastien Jacques, professor-researcher in electrical engineering at the University of Tours.

At a time when environmental protection is on everyone's mind, adopting a responsible attitude to avoid wasting energy in our home is essential.

According to EDF, nearly two-thirds of the energy we consume is intended for heating, whether via electricity or gas.

The last third is divided between hot water, cold (refrigerator, freezer) and the various uses requiring power (household appliances, lighting, air conditioning, IT, etc.).

Simple actions are often recommended to reduce your electricity bill.

For example, avoid increasing the temperature of the house in winter and follow the health recommendations which recommend a temperature of 19 to 20 ° C in living rooms and 18 ° C in bedrooms.

Lowering the temperature at home by one degree reduces your electricity bill by around 7%.

Another example is to postpone the operation of our electrical devices (washing machine, dryer, dishwasher) to certain time slots when electricity demand is low.

However, performing this type of action is not necessarily without constraint for users: for example, you have to think about programming your electric convectors or organizing the drying of the laundry after a washing cycle, which is not necessarily easy. at a time when electricity is cheapest.

A solution to implement these different principles of energy savings would be to have “smart” homes, which would program electrical devices at appropriate times, while adapting to users' habits.

But the smart home is based on a key element: an electricity storage system.

A look back at the concept of "smart" homes

We recently proposed a system to save electricity in individual homes.

This system consists of controlling the electrical equipment of the house, at appropriate times of the day and all without disturbing the habits of the occupants.

“Smart” actions are implemented by computer algorithms and connected sockets, to control each electrical device.

Such a system relies on three key elements: batteries to store electricity, an energy converter, and a computer algorithm making the system “intelligent”.

Indeed, when the electricity tariff is the lowest (in off-peak hours), the appliances in the house can operate thanks to the energy supplied by the distribution network.

When the electricity tariff is the highest (during peak hours), the batteries make the proposed system completely autonomous.

The electrical equipment of the house is then controlled by an energy converter, after having transformed the direct current into alternating current, makes it possible to control the electrical equipment of the house.

What storage capacity should we install at home?

The GREMAN research unit recently developed software that helps understand the value of the “smart” home to help households reduce their electricity bills.

Demonstrator of a connected and "intelligent" home presented in a fun form at the 27th edition of the Science Festival © Greman - Ecco

In order for the simulations to reflect reality, the software relies on comprehensive databases of consumption measurements.

These data come from around ten “control” houses.

By using this software, the battery can be judiciously chosen to optimize the household electricity consumption while limiting the total cost of the system.

To give a few orders of magnitude, let's take the example of a house of more than 70 m2, but with two types of main heating: either all electric or no electric heating.

In both cases, it is assumed that the household has a Peak hours / off-peak hours pricing option (50% of French households are now subscribed to this option).

In this example, the “smart” house has lead-acid batteries in order to keep the total cost of the installation as low as possible.

What storage capacity should we then install in these two cases?

What is the cost of the batteries?

In the first case (house with electric heating), the most favorable case, that is to say with a shift of all consumption of peak hours (taken here between 7 a.m. and 11 p.m.) in off-peak hours, corresponds with an energy capacity to be installed of 21 kWh, which is more than 50% higher than the Tesla “Powerwall” battery illustrated above.

If the main heating method of the house is not electric, then the capacity to be installed is only 7.2 kWh, which is almost twice as low as the “Powerwall” system.

Example of a home storage system, Tesla's “Powerwall” battery © Sébastien Jacques (via The Conversation)

The situation will be a little different if you use another type of battery.

For example, Although Lithium-ion (Li-ion) batteries are priced three times higher than lead-acid batteries, they now represent the bulk of the home battery market because they are much lighter, less dangerous. for health and the environment, and offer better energy efficiency.

Tesla's enormous “Powerwall” rechargeable battery, which is enjoying considerable success across the Atlantic, has attractive features in terms of storage capacity, energy efficiency, reliability and price.

Is such a system really profitable?

For a house of more than 70 m2 whose main heating method is electric, we have just seen that the capacity of the battery to be installed is 21 kilowatt-hours.

How many years are needed in this case to make this “intelligent” electricity consumption management system profitable?

This return on investment should be compared to the lifespan of batteries (lead in our example, or lithium-ion currently on the market), which can reach ten years.

Using software developed by the GREMAN research unit, simulation results show that it would take more than 100 years with a lead-acid battery-based system (more than 200 years with lithium batteries) to amortize the installation.

Depreciation of a prediction and management system using electricity storage © Sébastien Jacques (via The Conversation)

This unreasonable duration is explained today by the electricity tariff and in particular, the difference in peak / off-peak hour pricing, which is only around 4 euro cents per kilowatt-hour.

If we want a return on investment in five years, for a lead-acid battery technology, the price difference between peak hours and off-peak hours must be 52 euro cents per kilowatt-hour, or more than 14 times higher than today.

If lithium batteries are used, this difference must be greater than the euro per kilowatt hour.

What future for “smart” homes?

Today, an “intelligent” electricity consumption management system has its place in countries where the price difference between peak hours and off-peak hours is marked;

this is the case, for example, in Australia where the difference is around 30 euro cents per kilowatt-hour.

Our "Energy" dossier

In France, with the deployment of Linky-type smart meters, it is possible to program several tariffs for the electricity consumed depending on the time of day.

Even if these meters still generate a lot of debate on their performance as well as their “intrusive” nature or their impact on health, they could help make the “smart” home more profitable, and use electricity more efficiently. that we produce, including through renewable energies.


Energy poverty: a notion still unclear ten years after its introduction


Electric vehicles: Why their boom will make oil "the energy of the poor"

This analysis was written by Sébastien Jacques, professor-researcher in electrical engineering at the University of Tours (with the collaboration of Sébastien Bissey, Jean ‑ Charles Le Bunetel, Ismail Aouichak and Yves Raingeaud).

The original article was published on The Conversation website.

Declaration of interests

The GREMAN research unit ( of the University of Tours, the CNRS and the INSA Center Val-de-Loire has received funding from the Center Val- de-Loire within the framework of a project of regional interest (project n ° 2015-00099656).

  • Research

  • energy savings

  • electricity

  • energy

  • Video

  • Linky counter

  • Society