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You have decided to go solar, you request two quotes, and then doubt sets in: 6 kW or 9 kW? One seems a little too small, the other a little too expensive. And no one clearly tells you which one fits your home.
It is the most important decision in the entire project, and it is also the one most often decided backwards. Consider the common reflex: choose the largest option «for peace of mind». The problem is that targeting 9 kWp when you consume 6 means tying up several thousand euros to produce a surplus that you will sell for next to nothing. Conversely, staying with 6 kWp when you have a heat pump and an electric car means letting savings slip away — all the more painful since electricity prices rose sharply between 2022 and 2024.
The right level is therefore not a question of power in absolute terms. It is a question of your profile: what you consume, at what time, and under which roof. Let us see how to make the right decision.
Key takeaway: the amounts of solar subsidies (self-consumption premium, surplus feed-in tariff) are regularly revised, generally every quarter. VAT thresholds and eligibility conditions also change. Always check the values in force at the time of your quote on service-public.fr or with your installer.
What 6 kW and 9 kW really represent
A word about the terminology, because it catches everyone out. The power of a kit is expressed in kilowatt-peak (kWp): the maximum power delivered under standard sunlight conditions. When a seller talks about a «6 kW solar kit» or a 6000W solar kit, they mean the same thing: an installation of approximately 6 kWp. There is no trick here, just two ways of expressing the same figure.
How many panels for 6 kW and 9 kW?
With modern 450 to 500 Wp panels, here are the approximate figures:
- 6 kW solar kit: approximately 12 to 14 panels, covering 24 to 30 m² of roof area.
- 9 kW solar kit: approximately 18 to 20 panels, covering 36 to 45 m².
These square metres are not a minor detail. Many south-facing roof sections do not have enough space for a 9 kWp kit without extending onto an east- or west-facing section, which is less favourable. And a poorly exposed panel produces less. Your roof may therefore settle the debate before your consumption does — we will come back to this below.
What yield can you expect?
In France, you can expect between 900 and 1,400 kWh per installed kWp per year, depending on the region and orientation (approximate figures observed in residential operation). In concrete terms:
- 6 kWp produces an average of 6,000 to 8,000 kWh/year;
- 9 kWp produces an average of 9,000 to 12,000 kWh/year.
For context: a French household consumes an average of around 4,700 kWh of electricity per year, excluding heating. With electric heating, a heat pump or an electric car, this figure rises quickly — and this is precisely where the choice of power rating matters.
The real criterion: your consumption profile
The right power rating is not the one that produces the most. It is the one that best covers your consumption at the right times. That is the key point: the electricity you consume directly is worth much more than what you sell. Producing at midday is pointless if you are not at home to use it.
When a 6 kW solar kit is more than enough
The 6 kWp option is the standard for a typical French family home. It is suitable if:
- your annual consumption is between 4,000 and 8,000 kWh;
- you do not (yet) have a heat pump or an electric car;
- part of your consumption takes place during the day: working from home, a hot-water tank controlled during solar hours, or programmable appliances.
For this profile, a 6000W solar kit maximises the self-consumption rate while keeping the budget under control. It is often the best economic compromise, full stop. Our HYXiPOWER 6000W professional self-consumption solar kit is a good example of this category: a configuration designed for households that want to reduce their electricity bill without paying for surplus sold at a loss.
When switching to a 9 kW solar kit becomes worthwhile
The 9 kW solar kit becomes relevant when consumption is high and expected to increase. Choose it if:
- your consumption exceeds 8,000 kWh/year, or even 10,000 kWh;
- you heat your home with electricity or have a heat pump;
- you own or plan to purchase an electric car charged at home;
- you have a swimming pool, air conditioning, or several high-consumption electrical appliances.
One important detail: 9 kWp remains the power ceiling below which the simplest administrative and tax conditions apply to residential installations (more details below). Above this level, the project moves into another regulatory and tariff category. This is why 9 kWp serves as a «reasonable» upper limit for a detached home — not by chance, but because it is a threshold.
Comparison table: 6 kW or 9 kW solar kit
| Criterion | 6 kW solar kit | 9 kW solar kit |
|---|---|---|
| Number of panels (≈450-500 Wp) | 12 to 14 | 18 to 20 |
| Roof area | 24 to 30 m² | 36 to 45 m² |
| Average annual yield | 6,000 to 8,000 kWh | 9,000 to 12,000 kWh |
| Target household consumption | 4,000 to 8,000 kWh/year | 8,000 to 12,000 kWh/year |
| Ideal profile | Home without heat pump or electric car | Home with heat pump, electric car or swimming pool |
| Eligibility for subsidies | Below the 9 kWp residential ceiling | Below the 9 kWp residential ceiling |
Both power ratings remain below the 9 kWp threshold, which provides access to the most straightforward support schemes for private individuals (see the dedicated section). The exact amounts depend on the rate applicable on the date of your grid connection.
Roof and orientation: the constraint people forget
The choice does not depend solely on your consumption. Your roof has its own limits, and they cannot be negotiated.
Available space
A 9 kWp kit requires up to 45 m² of well-exposed roof area. If your south-facing section offers only 30 m², installing 9 kWp means placing panels on a less productive east- or west-facing section — reducing the efficiency per kWp. Do the calculation: a 6 kWp system entirely facing south can produce almost as much as a poorly distributed 9 kWp system, at a much lower cost. High power on the wrong roof means paying more to produce the same amount.
Orientation and tilt
In France, the ideal remains due south, tilted at 30 to 35°. An east-west orientation reduces the yield by around 10 to 20%. However, it spreads production throughout the day, which can improve the self-consumption rate. A serious design office includes these parameters when sizing the system, rather than reasoning in terms of raw power. Ask to see this calculation: it is what separates a solid quote from a rough guess.
Budget and profitability: what changes when moving from 6 to 9 kW?
The additional cost of a 9 kW system compared with a 6 kW system is mainly due to the extra panels and wiring. The inverter, connection labour and administrative procedures increase less than proportionally. As a result, the cost per kWp even decreases slightly as the power rating increases. On paper, the larger kit therefore seems like a good deal.
Except that there is a catch. Producing more is profitable only if you consume or make use of that production. The kWh you consume yourself saves you the full price charged by your supplier; the surplus you sell is paid at a much lower rate. Take your latest bill and compare the price per kWh you pay with the current surplus feed-in tariff (periodically revised by the CRE): in almost every case, self-consumption beats selling. Oversizing to sell surplus is therefore not an investment — it is rarely the right calculation today.
The simple rule to remember
Choose the power rating that maximises your self-consumption rate without making the surplus sold to the grid too high. For a household with moderate consumption, 6 kWp consumed at 70-80% often outperforms 9 kWp, a large share of which is sent to the grid at a low price. Bigger does not mean more profitable.
2026 subsidies: self-consumption premium, VAT and feed-in tariff
Support schemes change frequently. Rather than giving you amounts that may be out of date when you read this, here is how each subsidy works and where to check the exact rate. For full details, also see our guide to French government solar subsidies in 2026.
The self-consumption premium
For a self-consumption installation with surplus feed-in, an investment premium is paid under the purchase obligation scheme. Two things are important to understand:
- It is expressed in euros per installed kWp, and its amount is degressive: the higher the power rating, the lower the amount per kWp. A 6 kWp and a 9 kWp system are therefore not eligible for the same amount per kWp.
- The rate is revised every quarter by the CRE, based on the volume of connected installations. The applicable amount is the one in force on the date your complete grid connection application is submitted.
As these figures change every quarter, never rely on an old amount found online: check the up-to-date official rate on service-public.fr or ask your installer before signing.
Reduced VAT
Residential photovoltaic installations benefit from a reduced VAT rate for low-power systems, instead of the standard 20% rate. The exact scope — power threshold, technical conditions and installation by a qualified RGE installer — has recently changed and may change again. Keep the 9 kWp reference point in mind: below this ceiling, you remain within the most accessible conditions; above it, the project falls outside this favourable framework. As the criteria are cumulative and subject to change, ask your installer to confirm the exact rate applicable to your situation in writing on the quote, and cross-check it on service-public.fr.
Surplus feed-in
The surplus you do not consume can be sold under the purchase obligation scheme (for example, through EDF OA), at a tariff guaranteed by contract over the long term — around 20 years for photovoltaics. This feed-in tariff is periodically revised by the CRE and depends on the installation's power rating. It is deliberately lower than the price at which you buy your own electricity. This is not a flaw in the system, but a signal: the economic priority is direct self-consumption, not selling surplus.
What about all-in-one solutions with a battery?
The power rating is not the only lever. Energy storage changes the equation. A battery allows you to consume in the evening and at night the energy produced during the day, which significantly increases the self-consumption rate compared with a kit without energy storage — often from around 30% without a battery to over 70% with a properly sized energy storage system. The same sunlight, but used twice as effectively.
This is the key advantage of integrated systems such as the SigenStor all-in-one single-phase 6 kW solar kit, which combines a hybrid inverter and battery in a single unit. If your consumption is shifted towards the evening — returning from work or charging your car — pairing 6 kWp with a battery can outperform 9 kWp without energy storage. Once again, it is not the power rating that decides, but the time at which you draw electricity.
How to decide: the 4-question method
To choose between a 6 kW or 9 kW solar kit, ask yourself these four questions, in this order:
- What is my actual annual consumption? Review your bills for 12 months. Below 8,000 kWh, 6 kWp is often sufficient.
- Will my consumption increase? A heat pump, electric car or planned extension justifies choosing 9 kWp.
- Can my roof accommodate 9 kWp facing due south? If not, a well-oriented 6 kWp system is better than a scattered 9 kWp system.
- What is my hourly consumption profile? If I mainly consume electricity in the evening, a battery may matter more than raw power.
If you are still unsure, browse our range of self-consumption solar kits: each configuration is described with its power rating, expected yield and usage profile. This gives you a practical way to compare 6 kW, 9 kW and energy storage solutions using your own figures.
6 kW or 9 kW: the right choice is the one that fits your usage
There is no objectively «best» power rating. The 6 kW solar kit remains the benchmark for a family home with moderate consumption, offering the best price/self-consumption compromise. The 9 kW solar kit becomes worthwhile as soon as a heat pump, electric car or consumption above 8,000 kWh enters the picture — while remaining below the 9 kWp ceiling that provides access to the most favourable residential conditions in 2026.
The process can be summed up in three steps: size the system based on your bills, confirm feasibility on your roof, and factor in the subsidies currently in force. It is not a race for power — this approach is what makes the system profitable. To compare configurations side by side, including their power rating and yield, browse our self-consumption solar kits.
This article is provided for general information purposes only. Support schemes, their amounts and their conditions change regularly. Before making any decision, check the current information with official sources (service-public.fr) or a France Rénov' adviser.