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The energy transition will require the use of renewable energy resources that will allow us to reach our decarbonization objectives. In addition to states and institutions, individuals have an important role to play in this transition, particularly with the installation of photovoltaic panels. But for individuals to use this source of energy, they must be guaranteed a financial return that encourages them to take the plunge. Several companies, in a commercial approach, guarantee returns on investment after 2–3 years for any installation. But is the financial profitability always guaranteed? In France, several types of photovoltaic installations are possible, total resale and self-consumption. For each one, the profitability will vary and depends on many parameters such as the initial and daily investment, the irradiation, the electricity buy-back price, and the consumption. This paper explains the calculation methodology for both typologies and shows that currently, in most cases, a self-consumption installation is more profitable than a full resale installation but is far from obtaining the returns on investment predicted by the commercials. If self-consumption is more profitable today, this is due to the fact that the investment (initial or annual) is less important, and that the price of electricity becomes more and more expensive while at the same time the price of resale decreases from year to year.
Research Institute XLIM, University of Limoges, Limoges, France
Bruno Beillard
Research Institute XLIM, University of Limoges, Limoges, France
Serge Mazen
Research Institute XLIM, University of Limoges, Limoges, France
Julien Leylavergne
University Institute of Technology, University of Limoges, Limoges, France
*Address all correspondence to: quentin.lagarde@unilim.fr
1. Introduction
The price of electricity increases every year. Moreover, with the global geopolitical context and the French energy context (planned partial replacement of the nuclear part by renewable energies), the cost of energy is likely to increase further. In addition, the massive arrival of connected objects (IoT), the increase of the electric car fleet, the democratization of telecommuting which will be accompanied by an increase in residential consumption. Therefore, the French are looking for solutions to reduce their energy bill. One of the possibilities is the installation of devices producing electricity from renewable energy, such as photovoltaic solar panels, which appear today as the most promising option for 31% of the French [1].
Indeed, the installation of photovoltaic panels in France is growing. At the end of 2019, 4,54,934 photovoltaic installations were recorded, corresponding to an installed capacity of 9904 MW, including 28,683 new installations in 2019 alone (966 additional MW) [2].
Of the 37 million customers in France registered by Enedis, 1.23% have a photovoltaic installation. Thus, the capacity for panel installation is still immense.
In 2019, 87% of installations were below 9 kWp (57% <3 kWp, 30% >3 kWp, and < 9 kWp) proving that the French prefer house-scale installations, and that the notion of collective production has not yet fully arrived in France [3].
Moreover, self-consumption has been developing more than the total resale since 2015. Between 2018 and 2019, 85% of installations were for self-consumption with surplus sale (158 MW) or without sale and without injection (36 MW). But all the self-consumption finally represents only 1.95% of the total French solar park.
Nevertheless, 1 out of 2 French people find that the investment is too expensive and becomes a brake to the installation of panels.
But really, is the installation of photovoltaic panels advantageous in all situations for the individual?
The first difficulty for French people who want to invest in photovoltaic panels is to choose the type of their future installation. There are currently two main families.
The first is the total resale also called total injection (Figure 1) [4]. All the energy produced is resold to a supplier and is redistributed on the national grid. The supply of the house is classically done by the network. Here the individual will still be subject to the inflation of electricity. This type of installation is finally a simple financial investment in renewable energy.
Figure 1.
Total resale.
The second possibility is self-consumption, which has been widely developed in 2015 (Figure 2) [5]. The energy produced is primarily consumed directly by the individual. Some variants exist for the management of the surplus energy. It can either be injected into the grid and bought back by the supplier or not sold and then lost or stored in batteries or virtually. The self-consumption allows direct reduction of the electricity bill of a private individual.
Figure 2.
Self-consumption.
In the continuation of this article, the profitability of installation in total resale and in self-consumption with surplus will be compared.
n: the number of years, which is 20 years (time of the energy buy-back contract)
i: tilt of the panels
o: orientation of the panels
Epaverage: average energy produced over a year starting from an average irradiation
τself: self-consumption rate
THP: peak hour tariff in €/kWh
Tvt: feed-in tariff in €/kWh
ID: initial investment in €.
IA: annual investment in €/year
Infla: inflation of electricity
Infla2: Inflation of the annual investment price
The different parameters of the profitability calculation are explained in the following sections.
3.1 Initial investment ID
The material selected for the realization of a photovoltaic project is essential. It must have the best quality/price ratio, guaranteeing an optimal yield for at least 20 years.
To sell the electricity to a supplier, it is mandatory that the installation is carried out by a certified company.
The installation will vary depending on the installers, the material, and the geographical area and follows a price range according to the following equations (see Figure 3):
Figure 3.
High and low range of a photovoltaic installation in €/Wp according to the installed power in kWp in France.
Low range: 2.25-0.06*kWp €/Wp
High range: 3.29-0.13*kWp €/Wp
The price of the installation includes the solar panels, the inverters (inverters or micro-inverters), the decoupling relays, the cables, the protection boxes, the fixing kits, the transport, the labour, the security of the building site and the administrative procedures [6].
For example, an installation of 3 kWp of panels will cost the private individual with the installation by an approved installer and the price of the material between 6200 and 8700 €.
For the total resale, the connection fees of Enedis (Electricity Distribution System Operator) will be added. Prices vary according to the place of residence and the difficulty of connection. With a Linky meter, it is between 400 and 800 € and with the old meters between 1000 and 1400 €.
On the other hand, for self-consumption, mainly with resale of surplus, state bonuses are possible, ranging from 380 to 280 €/kWp depending on the power installed.
All the initial investments are summarized in Table 1.
First semester 2022
Total resale
Self-consumption with resale
Self-consumption without resale
Installation price (€/kWp)
between 2255–60*kWp and 3290–130*kWp
Between 2255–60*kWp and 3290–130*kWp
between 2255–60*kWp and 3290–130*kWp
Network connection (€)
between 400 and 1400
0
0
State aid (€/kWp)
0
< 3 kWp: 380 < 9 kWp: 280
0
Table 1.
The different sources of initial investment to be considered for the profitability calculation.
The price range of the initial investment as a function of the installed power, between the 2 blue curves (maximum and minimum investment possible according to Table 1) for the total resale or between the 2 red curves for self-consumption, is presented in Figure 4. The initial investment is more advantageous in self-consumption because there is no need for connection to the grid and there is also a premium from the state.
Figure 4.
Extremum for a starting investment ID for the total resale (blue curves) and self-consumption (red curves).
3.2 Annual investment IA
In addition to the initial investment, there are annual charges.
There is the “tariff for the use of public electricity networks,” or TURPE in French, created in 2000 to remunerate the electricity transmission network, Enedis and the local distribution companies [7]. It is currently 35.45 € including taxes/year for the total resale and 8.86 € including taxes/year for self-consumption with surplus resale (Figure 5). Since 2017, TURPE has changed very little over time and is cheaper for self-consumption.
Figure 5.
Evolution of TURPE over the years, for the total resale (blue curves) and self-consumption (red curves).
The maintenance of the installation (panels, inverters) can also be a source of expense, but it is generally carried out by the individual himself for small installations.
It can also have an overpricing of the home insurance; this data depends on the insurance of each, the contract closures, and so on.
These annual fees are re-evaluated every year, resulting in INFLA2 inflation. Since the beginning of self-consumption in France, the TURPE for PV has not increased (Figure 5). As the maintenance and insurance tariffs are variable to the situation, it is considered here that the annual investment inflation INFLA2 is 0%.
The total annual investments are summarized in Table 2.
First Semester 2022
Total resale
Self-consumption with resale
Self-consumption without resale
TURPE
35.45 €/year
8.86 €/year
0€/year
Maintenance
between 0 et 300€/year
between 0 et 300€/year
between 0 et 300€/year
Insurance
between 0 et 100 €/year
between 0 € et 100 €/year
between 0 et 100 €/year
Tax
0 €
0 €
0 €
Table 2.
The different sources of annual investment to be considered for the profitability calculation.
The price range for both full resale and self-consumption is shown in Figure 6. The blue curves represent the maximum and minimum price to be considered for the annual investment in the total resale and the red curves for self-consumption according to the possible variations in the TURPE, the price of insurance and maintenance. Taking the extremes, the price of the annual investment is one time cheaper in self-consumption due to the TURPE.
Figure 6.
Extremum for the cumulative annual investment IA over 20 years for total resale (blue curves) and self-consumption (red curves).
3.3 Solar energy production Epaverage
The average solar energy production Epaverage (kWh/year) follows Eq. (3).
Epaveragenio=∑1nGaverageio×ηn−1−ηn−1.P×S×PRnE3
Where:
n: 20 years
Gaverage(i,o): average global irradiation over a year depending on the tilt i and orientation o of the surface (kW/m2/year)
η: efficiency of a panel (%)
P: loss of yield of the panels over time (%)
S: total installed area (m2)
PR: performance ratio (%)
It is necessary to know the average irradiation over a year.
Solar irradiation is a radiometric quantity that measures the amount of solar energy received per unit area after considering atmospheric absorption and scattering. The measured value depends on the tilt of the sensor of the measuring device and its analysis spectrum. The irradiance will allow the calculation of the solar energy produced (kWh). This magnitude will depend, initially, on geographical locations, including the time of sunshine that will be different from one region to another (Figure 7), and the latitude, which will play on the path of the sun. For example, in Lille the irradiance for a horizontal surface is on average 1090 kWh/m2/year, in Toulon 1612 kWh/m2/year, and in Limoges 1261 kWh/m2/year. The irradiance data come from the PVGIS software [9], which allows us to know the irradiance according to the geographical area in Europe and North Africa.
Figure 7.
Average sunshine time in France in the cities of Limoges, Lille and Toulon [8].
It will also vary according to the tilt and orientation of the surface. For example, in Limoges:
for a tilt of 30° south, an irradiation of 1460 kWh/m2/year is estimated against 1377 kWh/m2/year for an irradiation at 60° south.
for an orientation at 30° east, the irradiation is 1203 kWh/m2/year.
For Limoges, the most important irradiation is obtained for a tilt of 36°, full south with 1467 kWh/m2/year on average (Figure 8).
Figure 8.
Variation in irradiation as a function of tilt and orientation according to PVGIS SARAH2 in Limoges in 2020.
Irradiation will also vary over time, daily (day/night, climatic variations) and monthly (seasonality) (Figures 9 and 10). Finally, it is never the same from one moment to another, from 1 day to another and from 1 year to another.
Figure 9.
Daily irradiation variation - 30° south in Limoges.
Figure 10.
Monthly variation of irradiation - 30° South in Limoges.
But the calculation of the solar production is not limited to the solar irradiation. It is necessary to know the characteristics of the panels with their yield, their loss over time and the total installed surface. Depending on the technologies and brands, all these parameters vary, ranging from a yield of 19–21% associated with loss of 0.25% per year to 0.55% per year depending on the panels (see Table 3).
Brand PV
Power Wp
surface m2
€/(Wp/m2)
module efficiency %
annual degradation %
Technology
Mono Perc Ecodelta
345
1.69
0.61
20.45
0.5
Monocrystalline Half-cell
Mono Perc DMECG
370
1.82
0.72
20.31
0.55
Monocrystalline Half-cell
Longi LR4 60 HIH
375
1.82
0.72
20.6
0.55
Monocrystalline PERC
Trina Solar Vertex S
400
1.92
0.74
20.8
0.55
Monocrystalline Mutli Busbars
Risen Titan S
400
1.92
0.76
20.8
0.55
Monocrystalline PERC
Shingled Ecodelta
400
1.88
0.77
21.3
0.5
Monocrystalline Shingled
Trina Solar Vertex S
390
1.92
0.78
20.3
0.55
Monocrystalline Mutli Busbars
Trina Honey Mono Perc
375
1.83
0.79
20.5
0.55
Monocrystalline PERC
JNL Solar Full black
320
1.67
0.90
19.78
?
Monocrystalline Full Black
Duonergy Bifacial glass–glass
375
1.85
0.91
20.22
0.4
Monocrystalline Bifacial glass–glass
Bisol Duplex
375
1.86
0.97
20.2
0.55
Monocrystalline Half-cell
Q.Cells Duo G8
362
1.79
1.00
20.1
0.54
Monocrystalline Half-cell without spacing
Mono Perc AE Solar
450
2.71
1.01
20.7
?
Monocrystalline Multi-busbar
Q.Cells Duo G9
335
1.72
1.12
19.4
0.5
Monocrystalline Half-cell without spacing
TrinaSolat Vertex S
400
1.92
1.18
20.8
0.55
Monocrystalline Multi-busbar
TrinaSolat Vertex S Full Black
390
1.92
1.18
20.3
0.55
Monocrystalline Multi-busbar
Q.Cells Duo ML G9
390
1.90
1.23
21.1
0.54
Monocrystalline Half-cell sans without spacing
Hyundai
400
1.96
1.26
20.4
0.55
Monocrystalline Shingled
LG NeON H
375
1.84
1.26
20.4
0.33
Monocrystalline Multi-busbar
Hyundai Ultra Black
400
2.02
1.31
20.4
0.55
Monocrystalline Shingled
SunPoxer Maxeon 5
430
1.90
1.89
22.7
0.25
Monocrystalline Black Contact
LG NeON R
365
1.73
2.09
21.1
0.6
Monocrystalline Black Contact
Table 3.
The different characteristics of solar panels useful for profitability calculations [10].
The PR depends on the losses due to shading, wiring, inverters or microinverters, temperature and so on. According to the study [11], the average PR is 79% whether with microinverters or inverters regardless of the geographical area and the size of the installation. Variations in the PR are possible from 69–91%.
Figure 11 shows the cumulative energy produced over 20 years as a function of the installed peak power. Depending on the panels presented in Table 3, the yield and its loss over time and the performance ratio (see Table 4), the energy produced will be more or less important. The two blue curves represent the maximum (meaning panels with the best performance ratio and yields) and the minimum (meaning panels with the worst performance ratio and yields) possible energy produced.
Figure 11.
Extremum for the cumulative solar production over 20 years for an irradiation fixed at 1460 kWh/year (Limoges 30° south).
Total resale
Self-consumption with resale
Self-consumption without resale
Gaverage (kWh/year)
Between 0 and 2500
Between 0 and 2500
Between 0 and 2500
η (%)
Between 19 and 21
Between 19 and 21
Between 19 and 21
P (%/year)
Between 0.55 and 0.25
Between 0.55 and 0.25
Between 0.55 and 0.25
PR (%)
Between 69 and 91
Between 69 and 91
Between 69 and 91
S (m2/kWp)
Between 4.4 and 5.2
Between 4.4 and 5.2
Between 4.4 and 5.2
Table 4.
The different sources of variability of the solar production EPaverage.
3.4 Feed-in tariffs Tvt
For the calculation of the profitability, it is also necessary to know the feed-in price of the Tvt electricity, resold to a supplier. At least until September 2022, the feed-in-tariff, dictated by the CRE (Commission for the Regulation of Energy) in the total resale is 17.89 and 15.21 c€/kWh for installations below 3 and 9 kWp, respectively (Table 5). Over time, these feed-in tariffs have been decreasing every 6 months (Figure 12). For self-consumption with resale, the feed-in tariff is currently 10 c€/kWh for any installation below 9 kWp and has not changed since the beginning of self-consumption (Figure 13).
Variable parameters
Total resale
Self-consumption
ID
Installation price (€/kWp)
2770–95 * kWp
2770–95 * kWp
Connection (€)
600
State aid (€/kWp)
380 if ≤3 kWp 280 if ≤9 kWp
IA
TURPE (€/year)
35.45
8.86
Maintenance (€/year)
0
0
Insurance (€/year)
0
0
Infla (%)
3
Infla2 (%)
0
0
Tvt (€/kWh)
0.1789 if ≤3 kWp 0.1521 if ≤3 kWp
0.10
THP (€/kWh)
0.1841
Epaverage (kWh/year)
Gaverage (kWh/m2/year)
1460 (Limoges 30° south)
1460 (Limoges 30° south)
η (%)
20.5
20.5
P (%/year)
0.5
0.5
S (m2/kWp)
4.9
4.9
PR (%)
79
79
Table 5.
Data of the variables used for the profitability calculation. The example is for an installation in Limoges with panels arranged 30° south and average characteristics.
Figure 12.
Evolution of the electricity buy-back (orange curves) and of the state premium (blue curves) over the years for installations below 9 kWp in self-consumption.
Figure 13.
Evolution of the electricity buy-back over the years for installations below 9 kWp in total resale. Until 2017, the blue and red curves are mixed.
The feed-in tariff is fixed according to a 20-year locked-in contract with the supplier. It will not change over time for the individual once the contract is signed.
3.5 Energy tariff TH
For self-consumption, the evolution of the price of electricity will have an impact on the profitability of the installation. In France, to summarize, it is possible to choose an off-peak/peak hour subscription or a basic subscription. The tariffs will be different according to the subscription and according to the time of the day with an off-peak/peak hour subscription.
According to the regulated tariffs of the CRE, the price of electricity has been increasing steadily for both subscriptions as shown in Figure 14 with a much higher increase for off-peak hours than for peak hours.
Figure 14.
Evolution of regulated electricity tariffs in France according to the CRE for daytime (peak hours), nighttime (off-peak hours) and basic tariffs (same tariff all day).
In self-consumption, it is preferable to choose off-peak hours HC – peak hours HP contract rather than the basic price because it is during the peak hours HP (most expensive rate) that the solar production will intervene.
The price of electricity is currently 0.1841 €/kWh in HP (between 6 h30 and 21 h30) and 0.1470 in off-peak (between 21 h30 and 6 h30). Please note that the off-peak/peak hours may vary slightly from one area to another.
In addition, for the last 10 years, the price of electricity has been rising steadily, generating an INFLA inflation of about 3%/year for the off-peak/peak hour rates (Figure 14).
3.6 Self-consumption rate τself
The self-consumption rate is the proportion of energy directly consumed on site. This parameter is only useful for calculating the profitability in self-consumption.
The annual self-consumption rate τself follows Eq. (4).
The surplus being the moment when the production is higher than the consumption (Eq. 6).
For the calculation of surplus, it is necessary to know the consumption and production or by substitution the irradiation (Eq. 5), at an identical time scale and the shortest possible time to have a rate of self-consumption as realistic and accurate as possible.
To try to take at best the consumption variabilities, the Linky communicating meter will allow to recover the consumption data and thus the load curves by semi-hourly steps. For the example of the profitability calculation of this article, the load curve recovered is for an all-electric household (water heater, electric heating) of four people and 100 m2, in the countryside near Limoges, for the year 2019 with an average consumption of 15,000 kWh/year. The load curves are in red in Figures 15–17. Note that, for all other houses, the load curve will be completely different because it depends on the household appliances, the heating system, the insulation, the surface, the number of people, the habits of each person and so on.
Figure 15.
Solar production for a 3 kWp installation at 30° south in 2019 in Limoges (yellow curve) and load curve in 2019 for a house of four people, all electric, in Limoges (red curve). The green curve represents the annual average of production over the year 2019.
Figure 16.
Zoom-in January solar energy for 2.84 kWp 30° South in Limoges in 2019 and load curve 2019 for a house of four persons, all electric, in Limoges.
Figure 17.
Zoom-in July solar energy for 2.84 kWp 30° south in Limoges in 2019 and load curve 2019 for a house of four persons, all electric, in Limoges.
For the production variability, PVGIS [9] will give the irradiance for any location, tilt and orientation in Europe and North Africa following the calculation methods detailed in [12, 13, 14, 15]. The SARAH [16] and ERA5 [17] data give irradiances in hourly steps from 2005 to 2020. To reduce the hourly step to a semi-hourly step, the values of SARAH (satellite passage at 00:00–1:00 - …) and ERA5 (satellite passage at 00:30–1:30 - …) have been switched for the year 2019. The production curve for 3 kWp 30° south in Limoges is represented by the curves in yellow in Figures 15–17.
Moreover, the rate of self-consumption will vary according to the layout of the installation. Indeed, the surplus will be less important if the production is less and better adapted to the consumption curve. For example, the self-consumption rate is more important if the panels are oriented east rather than south (Figure 18) or if the installation is in a less sunny geographical area (Figure 19). Be careful that a higher self-consumption rate does not necessarily mean a higher yield (Figure 20).
Figure 18.
Self-consumption rate according to the installed power according to different tilts (30° and 60°) and orientations (south or east) for the city of Limoges and for a typical consumption of a house of 100 m2 for 4 persons with electric heating.
Figure 19.
Self-consumption rate according to the installed power for different cities (Limoges, Lille and Toulon) for installations inclined at 30° and oriented south and for a typical consumption of a house of 100 m2 of 4 persons with electric heating.
Figure 20.
Self-consumption rate according to the installed power separated in two seasons, summer (from April to September) and winter (from October to March), for the city of Limoges and for a typical consumption of a house of 100 m2 for four persons with electric heating.
Starting from Eqs. (1) and (2) for total resale and self-consumption, respectively, as well as Eq. (3) for the average energy produced, the values of each variable are shown in Table 5 and will be used for an example of profitability curve.
The values of the variables are chosen for a specific case, but they are adjustable according to the many parameters exposed in part III. The example here is for an installation in Limoges with panels placed 30° south and average characteristics of what is currently found. For self-consumption, the load curve is recovered for an all-electric household (water heater, heating) of four people and 100 m2, in the countryside near Limoges, for the year 2019 consuming an average of 15,000 kWh/year.
For any installed power from 1 to 9 kWp under the conditions of an irradiation of 1460 kWh/m2/year, self-consumption is more profitable, ranging from a gain over 20 years of 2500€ for 1 kWp to 14,500€ for 9 kWp. On the other hand, in the total resale of the installations, lower than 1 kWp is not profitable but can still generate gains of 11,500€ for 9 kWp (Figure 21). Consequently, the year from which the installation is amortized arrives well before (Figure 22) for self-consumption, approximately 12 years for any installed power against 15–16 years for the total resale on small installation and being able to go down to 12 years for a 9 kWp. On the other hand, the range of profitability for the same irradiation is large according to the variables. The curves of the extremes were obtained by starting from Figures 4, 6 and 11. In the most pessimistic case, after 20 years of the contract, the installation will still not be amortized whatever the installed power and the typology of installation.
Figure 21.
Comparison of the gains reported by an installation after 20 years of the contract for different installed powers for total resale and self-consumption in Limoges disposed 30° south according to the average variables and their extremums.
Figure 22.
Comparison of the years from which the photovoltaic installation becomes beneficial for different installed powers for the total resale and self-consumption in Limoges disposed 30° south according to the average variables and their extremums.
In addition, to compare the gain from solar production to a Pfinancial investment over several years, Eq. (7) is used.
Pfinancial=Gainnio+IDID1n−1×100E7
The financial investment Pfinancial shows the interest rate that the initial investment would yield if it had been put in the form of an investment in percentage per year during the 20 years of the contract.
Contrary to the gain, for self-consumption, a small installation corresponds to a more interesting financial investment that can go in our example to an equivalent investment of 3% per year for 20 years for the individual (red curve in Figure 23). On the other hand, for total resale (blue curve in Figure 23), the larger the installation, the more interesting the investment becomes over 20 years.
Figure 23.
Comparison of the interest rates that an installation would earn after 20 years of the contract for different installed powers for the total resale and self-consumption in Limoges located at 30° south.
Figures 24–26 show, respectively, the 3 criteria of profitability (earnings, year of amortization and interest rate) for installations of 3 and 9 kWp in the total resale by starting again from the criteria of Table 5.
Figure 24.
Comparison of the gains reported after 20 years of the contract for installations of 3 and 9 kWp according to different irradiances corresponding to installations with different orientations, tilts, and geographical areas for total resale.
Figure 25.
Comparison of the years from which the photovoltaic installation becomes beneficial for installations of 3 and 9 kWp according to different irradiances corresponding to installations with different orientations, tilts and geographical areas for the total resale.
Figure 26.
Comparison of the interest rates that an installation would earn after 20 years of the contract for installations of 3 and 9 kWp according to different irradiances corresponding to installations with different orientations, tilts and geographical areas for the total resale.
These curves allow us to show that the profitability in the total resale is more important for big installations and for higher irradiations, depending as well on the geographical zone or on the orientation and tilt of the installation. Examples of profitability have been placed according to geographical areas well exposed (Toulon and Lille) and according to orientations (east and south) and tilts (30° and 60°) of the different panels.
For self-consumption, Figures 27–29 show the profitability according to the same three criteria (earnings, year of amortization and interest rate) as before for a 9 kWp photovoltaic installation. The higher the average irradiation over a year and the higher the self-consumption rate, the higher the profitability.
Figure 27.
Comparison of the years from which the 9 kWp PV installation in self-consumption becomes beneficial according to different irradiances and self-consumption rates and based on the variables presented in Table 5.
Figure 28.
Comparison of the gains reported after the 20 years of the contract for a 9 kWp installation installed in self-consumption according to different irradiances and self-consumption rates and using the variables presented in Table 5.
Figure 29.
Comparison of the interest rates that an installation would earn after 20 years of the contract for a 9 kWp installation installed in self-consumption under different irradiances and self-consumption rates and based on the variables presented in Table 5.
In the figures, different points have been placed corresponding to different geographical areas (Limoges, Lille or Toulon), orientations (south or east) and tilts (30° or 60°) of the panels and the consumption of the house according to an electric heating or not by making the hypothesis that the rate of self-consumption of a house without electric heating was the same in the year as the rate of self-consumption of the summer part (Figure 20).
For example, an installation in self-consumption of 9 kWp, located in Limoges (center of France), inclined 30° and oriented south with a consumption of 15,000 kWh/year (a house with electric heating) corresponds to an average irradiation of 1460 kWh/year and a rate of self-consumption of 30.8%. In this situation, the gain after 20 years will be 14,250 €, allowing to make the installation profitable after 11 years and corresponding to an investment of about 2.63% per year over 20 years. For the same installation but with a consumption not using electric heating, the irradiation is the same, but the rate of self-consumption becomes weaker, of 21.3%. Thus, the profitability will be less because the gain will be 11,370 €, allowing us to make the installation profitable after 12 years and corresponding to an investment of about 2.09% per year over 20 years.
Also, the fact that the orientation and the tilt of the panels differ from the optimum (30° south) increases the rate of self-consumption but decreases the irradiation, not allowing us to have a more important profitability, quite the contrary.
Self-consumption is developing more and more in the past years instead of the installations in the total resale. And for good reason, in addition to participating in the energy transition, a self-consumption installation is an interesting alternative for a monetary investment.
Indeed, currently with a buy-back price of electricity that is increasingly low for the total resale, self-consumption is in most cases more profitable for installations at home ranging from 1 to 9 kWp.
The benefits are more advantageous in the case where the irradiation is maximum on average over the year, 30 to 40° south, although the correlation consumption/production is the worst.
Moreover, the calculations of profitability were made for 20 years because it is the time of the contract of repurchase of the electricity proposed by EDF. But at the end of this contract, nothing prohibits to renew it. The initial investment being already amortized and having no repurchase of material (life span of the panels higher than 30 years and that of the micro-inverters of 25 years), the profitability will be only better than that calculated here.
Also, the profitability in self-consumption can be improved by using an energy management. Indeed, if appliances are used at the most opportune moments, when there is a surplus, the rate of self-consumption, the quantity of energy produced that is directly consumed on site and not lost or resold at low cost, will only be better. If for example, the water heater, the washing machine and so on are launched at the time of the surplus to the link of evening, the rate of self-consumption will increase and consequently the profitability will improve.
Note that for each calculation of profitability in self-consumption, the calculations are entirely to be redone because each household has its own consumption habit.
Thus, it would be interesting to make profitability calculations for different load curves: household without electric heating (represents 80% of the houses), household of two persons, household of six persons, household of retired person and so on. The electrical energy can be divided or multiplied by 2 or 3, with different consumption habits.
Finally, investing in photovoltaic seems to be interesting in all cases (total resale or self-consumption with sale of surplus). But to privilege the self-consumption seems to be the most judicious especially as the inflation of electricity has great chance to increase more quickly than in the past, having as a direct effect an increase in the profitability of an installation in self-consumption.
This work is part of the UNIVEERS and LIMBATT project, co-financed by the European Union in the framework of the FEDER-FSE 2014-2020 and by the Nouvelle-Aquitaine region.
energy regulation commission (Commission de régulation de l’énergie in French)
Epavearge
average energy produced over a year based on an average irradiance
Gaverage
average irradiance
THP
peak hour tariff
Tvt
feed-in tariff
ID
initial investment
IA
annual investment
Infla
inflation of electricity
Infla2
inflation of the annual investment price
TURPE
tariffs for the use of public electricity networks
kW
kilowatt
kWh
kilowatt hour
kWp
kilowatt peak
PR
performance ratio
PV
photovoltaic panel
W
watt
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Written By
Quentin Lagarde, Bruno Beillard, Serge Mazen and Julien Leylavergne
Submitted: 14 October 2022Reviewed: 05 January 2023Published: 22 March 2023
Open access peer-reviewed chapter
