Energy renovation: the government wants to reduce certain subsidies, but what do the figures actually say?

According to a study conducted by Hello Watt using actual consumption data from 900.000 homes equipped with Linky and Gazpar smart meters, not all energy renovation work offers the same level of energy savings, but each meets different objectives.

The main findings of the study

The study highlights several key findings regarding the actual effectiveness of major energy renovation projects:

• Air-to-water heat pump: 62 % OFF average heating consumption, or approximately €886 in savings per year for a home previously heated with gas^[3].
• Solar panels: reduction of 32% to 43% electricity drawn from the grid, depending on the presence or absence of a storage battery^[4].
• Monitoring consumption using smart meters: active users of the Hello Watt app reduce their electricity consumption by an average of 10%, About €123 in savings per year^[15].
• Attic insulation: average reduction in 6% of electricity consumption and 7% of gas consumption.
• Wall insulation: reduction in 7% of electricity consumption and up to 16% for homes heated by gas.
• Window replacement: more modest savings, from 3% on electrically heated dwellings and 5% for those heated by gas^[5].

The study thus shows that the energy savings generated by insulation work are very real, even if they generally remain lower than the performance of heat pumps or photovoltaic installations.

A refocusing of MaPrimeRénov' on the most energy-efficient renovations

In a context of controlling public spending, the government wishes to concentrate MaPrimeRénov' aid on operations considered most effective in sustainably reducing energy consumption in homes.

From September 1, 2026, subsidies for most isolated ("single-action") work should therefore disappear, particularly for:

• attic insulation
• roof insulation
• window replacement

These works will, however, remain eligible when they are part of a large-scale renovation, while energy savings certificates (CEE) will continue to finance part of these operations.

Conversely, subsidies for the installation of an air-to-water heat pump, a central element of the government's electrification plan presented in the spring of 2026, are maintained.

This approach is based on a simple principle: reserving public funding for projects offering the greatest energy savings.

But does this strategy truly reflect the performance observed on the ground?

A study based on the actual consumption of 900.000 homes

To answer this question, Hello Watt relied on data from 900.000 homes sharing their daily electricity (Linky) and gas (Gazpar) consumption via its application.

In order to measure the specific impact of each type of work, the study selects a sample of 2.500 housing having at least twelve months of consumption before and after the work^[1]Only dwellings heated exclusively by electricity or gas and having undergone only one type of renovation were included in the analysis.^[2].

This methodology makes it possible to evaluate the savings actually observed after the work, and not just the theoretical performances calculated during thermal studies.

The heat pump confirms its status as the most efficient solution.

Among the various equipment analyzed, the air-to-water heat pump appears to be the most effective lever for sustainably reducing energy consumption in homes heated with gas.

Data collected by Hello Watt shows an average decrease in 62% of the energy consumption dedicated to heating after replacing a gas boiler with an air-to-water heat pump. For a typical household, this represents a saving of approximately € 886 per year on the energy bill^[6].

In detail, this change translates into an average decrease in 11.600 kWh of gas per year, offset by an increase of approximately 4.400 kWh of electricity consumption, the heat pump uses electricity to operate.

These results are consistent with those published by ADEME, which estimates the average coefficient of performance (COP) of a heat pump at 2,9while noting that actual performance depends heavily on the size of the installation, the quality of its implementation, and its adjustment^[7].

In other words, a heat pump consumes on average 2,6 times less energy than a gas boiler producing the same amount of heat.

Technology at the heart of the government's strategy

These performance characteristics explain why the heat pump remains today the main equipment supported by MaPrimeRénov'.

Depending on the combined MaPrimeRénov' and Energy Savings Certificates (CEE) schemes, the aid can reach 10.800 € for the most modest households, while higher-income households continue to benefit from CEEs.

For a middle-income household living in a house 130m² in Amiens and consuming 13.000 kWh of heating per year, Hello Watt estimates the average remaining cost to be 6.450 €, meaning an investment that is recouped in about seven years[8].

Beyond energy savings, heat pumps also offer advantages in terms of property value. Their installation generally results in an improvement of one to two classes on the Energy Performance Certificate (EPC), with a potential impact on the property's value.

From an environmental perspective, Hello Watt also estimates that replacing a gas boiler with a heat pump reduces CO₂ emissions by approximately 85%, Almost two tonnes of CO₂ avoided each year for housing.

The air-to-air heat pump also confirms its appeal.

Often considered a simple reversible air conditioner, the air-to-air heat pump represents more than 80% of installed heat pumps and it too displays significant performance.

The analyzed data shows an average reduction of 27% of energy consumption related to heating when it replaces electric radiators^[9].

Over the course of the year, this represents a decrease of approximately 12% of the total electricity consumption of the dwelling^[10].

These results are all the more interesting given that summer consumption mechanically increases with the use of air conditioning. Hello Watt thus observes an average increase of approximately 10% consumption during the summer.

In most cases, this performance is still achieved even though air-to-air heat pumps are generally only installed in the main living areas, with electric radiators often being kept in bedrooms or bathrooms.

Solar panels significantly reduce dependence on the electricity grid

While heat pumps dominate in terms of reducing heating consumption, photovoltaic installations appear to be the most effective lever for reducing electricity purchases from the grid.

The study shows that a solar installation can reduce 32% the amount of electricity drawn from the grid, or approximately €395 in savings per year for an all-electric home^[12].

When the installation is combined with a storage battery, the drop reaches 43%representing up to €531 in annual savings^[12].

These results are based on the analysis of data from 13.000 equipped homes battery-free photovoltaic panels and 200 houses equipped with a storage battery, cross-referenced with meteorological data, installed power and housing consumption^[11].

Profitability has now been achieved despite the reduction in subsidies.

While subsidies for residential solar energy (self-consumption bonus and buyback tariff) were significantly reduced in June 2026, Hello Watt believes that this technology remains economically relevant.

The company is assessing the cost of installing 6 kWc without battery 9.490 €with a return on investment time of approximately 10 years, for an average self-consumption rate of 52%^[13].

With a battery, the cost reaches 13.090 €, but the return time drops to 9 years, thanks to a self-consumption rate increased to 74%.

While the initial investment is typically recouped within about ten years, photovoltaic panels continue to produce electricity for several decades afterward, their lifespan frequently exceeding [a certain threshold]. 40 years.

An accelerator of home electrification

Hello Watt's data also highlights an interesting behavior of households already equipped with photovoltaic panels.

Among them :

• 25% also own an electric vehicle, compared to only 8% other users
• 35% also have a heat pump, compared 10% among households without equipment

For Hello Watt, solar power often constitutes a first step towards a broader electrification of energy uses in the home.

Monitoring your consumption: a still underestimated way to save money

Energy renovation isn't just about construction work. Data analyzed by Hello Watt also shows that a better understanding of one's consumption can already significantly reduce energy costs.

Active users of the Hello Watt app, which uses data from Linky and Gazpar smart meters, are experiencing an average decrease in 10% of their electricity consumption between two winters. For an all-electric household, this represents approximately €123 in savings per year^[15].

The most engaged users, who regularly check their consumption tracking, even achieve an average reduction of 16%.

These results confirm the findings of several research studies, including a study published by the CNRS in 2012, which found that households with precise knowledge of their energy consumption more easily modify their behavior and reduce their energy expenditure more significantly.^[14].

Deployed between 2015 and 2023 by Enedis and GRDF, smart meters thus appear as a decision-making tool that is still insufficiently used, even though they allow individuals to quickly identify the main areas of consumption and adapt their usage.

Insulation: measurable savings... but a benefit that goes beyond just the bill

This is probably the most sensitive point of the reform undertaken by the government.

Attic insulation, wall insulation, and window replacement are among the works for which MaPrimeRénov' assistance per gesture is due to disappear or has already been eliminated.

The argument put forward is that their energy efficiency is deemed insufficient in relation to the public investments made.

However, the data analyzed by Hello Watt provides a more nuanced perspective.

Real savings

The consumption figures observed after the work show an effective decrease in energy needs.

Attic insulation:

• 6 % OFF of electricity consumption, or approximately €74 saved per year^[16]
• 7 % OFF of gas consumption, or approximately € 82 per year^[17]

Wall insulation:

• 7 % OFF of electricity consumption, or approximately €86 in annual savings^[16]
• Up to 16 % OFF of gas consumption, or nearly € 189 per year^[17]

Window replacement:

• 3 % OFF of electricity consumption, or approximately € 37 per year^[16]
• 5 % OFF of gas consumption, or approximately 59 €^[17]

Savings are generally greater in homes heated with gas, where heating accounts for the majority of energy consumption, unlike all-electric homes where other uses (hot water, appliances, cooking...) occupy a larger share[18].

Results consistent with public studies

These figures are not isolated.

They agree with the conclusions of a study published in July 2025 by INSEE and SDES, which observed very similar orders of magnitude:

Attic insulation:

• -5,4% electricity
• -8,9% gas

Wall insulation:

• -5,4% electricity
• -13,9% gas^[19]

This convergence strengthens the credibility of the results observed by Hello Watt.

Why are the savings sometimes lower than theoretical estimates?

At first glance, these results may be surprising.

The performance figures reported in thermal studies are often higher than the actual energy savings observed.^[20].

In reality, this difference is largely explained by the lifestyle habits of the occupants.

The most energy-intensive homes are also very often underheated before the work.

In other words, their occupants voluntarily limit their heating in order to contain their energy expenses.

Once the home is better insulated, part of the savings is used to improve interior comfort rather than just reducing the bill.

This is what specialists call the rebound effect.

Thus, a house of 100 m², energy efficiency rating G. theoretically should consume more 22.000 kWh per year according to the model used for the Energy Performance Diagnosis.

However, the actual observed consumption levels are more around 11.000 kWh per year.

Insulation work not only reduces consumption, but also significantly improves the comfort of the occupants by limiting the sensation of cold walls, drafts and summer overheating.

In other words, their value cannot be assessed solely by looking at the energy savings achieved.

The work continues to be supported... but differently.

Even though MaPrimeRénov' is gradually disappearing for several insulation projects, these projects are not disappearing completely from the aid schemes.

The Energy Savings Certificates (ESC) continue to finance part of the operations.

Thus, for a house of 100m²Hello Watt estimates that insulating attics with fiberglass remains affordable starting at around 1.300 € after deduction of CEEs for a household with intermediate incomes.

This operation remains one of the most profitable, as attics generally represent 20 to 30% of a home's heat loss.

External thermal insulation, on the other hand, remains a much larger investment.

For a house of 100m²its cost is estimated at approximately 23.000 € after deduction of available aid for a middle-income household.

Which projects offer the best return on investment today?

The Hello Watt study highlights that not all energy renovation work pursues the same objectives. Some projects significantly reduce energy consumption, while others primarily improve thermal comfort, quality of life, and the property value of homes.

Comparison of the main works analyzed

Energy efficiency... but also benefits that aren't measured solely in kWh

The results of the study generally confirm the government's choice to maintain subsidies for equipment offering the greatest energy savings, particularly heat pumps.

However, concluding that insulation work would be of little use would be an oversimplification.

While insulating attics, walls, or replacing windows may generate more modest energy savings than heat pumps, their benefits far exceed simply reducing the bill.

They sustainably improve comfort in both winter and summer, reduce the phenomenon of cold walls, limit summer overheating, contribute to the preservation of buildings and help improve the Energy Performance Diagnosis (DPE), a criterion that is now crucial for the value of housing.

This distinction is essential: a successful renovation is not just about the kilowatt-hours saved.

Solar power: a major omission in the government's strategy?

The other significant lesson concerns photovoltaics.

While solar installations help to reduce 32 to 43% Electricity withdrawals from the grid, based on their level of self-consumption, and their support schemes were significantly reduced in the spring of 2026.

According to Hello Watt, this development appears paradoxical, as residential solar power also promotes the gradual electrification of homes.

The study notably shows that households already equipped with photovoltaic panels invest much more frequently in a heat pump or an electric vehicle, illustrating the role of solar power as a first step in a more global energy transition.

Beyond the work itself, better understanding one's consumption remains one of the most effective levers

The study also points out that energy renovation does not only involve significant investments.

Simply monitoring your consumption regularly using data from smart meters can already lead to significant savings.

Active users of the Hello Watt app thus reduce their average electricity consumption by 10%Or 16% for the most committed.

This result underlines the importance of energy monitoring tools, which are still relatively undervalued in public policies.

A study that sheds light on the debate without settling it.

The data and results presented in this article come from a study conducted by Hello Watt. BATINFO offers a summary and editorial perspective.

The data collected by Hello Watt provides particularly interesting insights into the actual performance of major energy renovation projects, based on observed consumption in 900.000 housing equipped with Linky and Gazpar meters.

They confirm that heat pumps are currently the most effective equipment for reducing energy consumption, which explains their central place in the government's strategy.

However, they also show that insulation work remains highly relevant, even when energy savings are more limited than expected. Its contribution to thermal comfort, the quality of life of occupants, and the increase in property value is a crucial element that cannot be reduced solely to the number of kilowatt-hours saved.

Finally, the study highlights the growing interest in residential solar energy and consumption monitoring tools, two levers that also contribute to the sustainable reduction of consumption and the electrification of uses.

At a time when MaPrimeRénov' is evolving to concentrate public funding on the operations deemed most efficient, these results remind us that the success of an energy renovation rests above all on a comprehensive approach, adapted to the characteristics of each dwelling and the needs of its occupants.

Beyond budgetary considerations, these results primarily demonstrate that the choice of energy renovation work cannot be guided by a single indicator. Energy savings, comfort, property value enhancement, and CO₂ emission reduction are all criteria to be taken into account when developing a truly effective renovation strategy.

To remember :

• The heat pump remains the most effective solution (-62%)
• Insulation work remains worthwhile despite more modest savings.
• Solar panels reduce electricity purchases by 32 to 43%
• Consumption monitoring already allows for savings of up to 10%.
• A successful renovation is not just about kWh saved.

References and methodology

[1] The analysis is based on a sample of 2.500 homes with at least twelve months of consumption data before and after work, out of the 900.000 homes sharing their data via the Hello Watt application.

[2] Only dwellings heated exclusively by electricity or gas and having carried out only one type of work were included in the analysis.

[3] Home formerly heated with gas (14.000 kWh/year of gas, type 2 consumption, climate zone 2, 3.500 kWh/year of electricity, Base tariff 6 kVA) switching to an air-to-water heat pump.

[4] All-electric house consuming 10.000 kWh/year (peak/off-peak hours option with 40% consumption in off-peak hours, 9 kVA subscription).

[5] Savings are greater for homes heated with gas, where heating accounts for the majority of energy consumption. The characteristics of the dwellings can also influence the results.

[6] Same home assumption as reference [3], with replacement of gas heating by a heat pump.

[7] ADEME – Opinion on the actual performance of heat pumps, published on October 7, 2025.

[8] Hello Watt study (May 2026): 130 m² house located in Amiens, middle-income household, annual heating consumption of 13.000 kWh.

[9] According to ADEME, an air-to-air heat pump should theoretically divide heating consumption by 1,8. The results observed by Hello Watt are lower because electric radiators are often retained in some rooms.

[10] Hello Watt analysis of 227 households that replaced all or part of their electric radiators with an air-to-air heat pump.

[11] The results concerning photovoltaic panels are based on the analysis of 13.000 houses equipped without a battery and 200 houses equipped with a battery, cross-referenced with meteorological data and injection data.

[12] All-electric house consuming 10.000 kWh/year (HP/HC, 40% HC, 9 kVA).

[13] The price generally observed on the market for a 6 kWp photovoltaic installation without battery is between €9.500 and €14.000.

[14] CNRS – Electricity consumption: the more informed we are, the less we consume, study published in 2012.

[15] All-electric house consuming 10.000 kWh/year (HP/HC, 40% HC, 9 kVA).

[16] Reference used for electricity savings calculations: all-electric house consuming 10.000 kWh/year (HP/HC, 40% HC, 9 kVA).

[17] Reference used for gas savings calculations: gas-heated house consuming 14.000 kWh/year of gas and 3.500 kWh/year of electricity.

[18] The differences in consumption observed between dwellings heated by electricity and gas are explained in particular by the weight of heating in total consumption as well as by the characteristics specific to each dwelling.

[19] INSEE – SDES, Effects of thermal insulation of dwellings on actual residential energy consumption, published on July 10, 2025. The results observed are close to those of the Hello Watt study.

[20] The savings actually observed after insulation work are generally lower than the theoretical savings calculated during thermal studies, part of the gain being devoted to improving the comfort of the occupants rather than solely to reducing consumption.

Illustrative image of the article via Depositphotos.com.