Glossary
Onduleur: the solar inverter in a PV installation
Quick definition
An onduleur (inverter) converts the direct current (DC) produced by solar panels into alternating current (AC) that your appliances can use and that can be exported to the grid. Without an inverter, solar panels produce electricity you cannot use. It appears on every solar PV quote. The inverter type, efficiency rating, and warranty period are worth paying attention to: it's typically the first component in a solar system that needs replacing.
What types of inverter appear on solar quotes?
There are four main types used in residential solar installations in France:
- String inverter (onduleur central): the standard configuration. All panels are wired in series into one or more strings, each connected to the central inverter. Reliable, cost-effective, and easy to maintain. The main limitation is that if one panel is shaded or soiled, the output of the entire string drops. Works well on unobstructed south-facing roofs where all panels receive similar irradiance.
- Microinverters (micro-onduleurs): one small inverter per panel, mounted on the panel frame. Each panel operates independently, so shading on one doesn't affect the others. More expensive per kWp than a string inverter, but better suited to roofs with complex orientations, nearby trees, or regular partial shading. Also allows panel-level monitoring.
- Hybrid inverter (onduleur hybride): includes battery management built in. Can charge and discharge a home battery storage system and switch between grid, solar, and battery sources. Required if you want battery storage as part of the installation, or if you want to add it later without replacing the inverter.
- String inverter with power optimisers (optimiseurs de puissance): a compromise between string and micro. Optimisers are fitted to each panel and allow independent MPPT tracking, reducing the shading penalty, while still routing current to a central string inverter. Less expensive than microinverters but with similar shading resilience.
Key specifications to check on a devis
When comparing solar quotes, look for these figures on the onduleur:
- Power rating (kVA or kW): should match or closely follow the peak DC output of the panel array. Slight undersizing (5-10%) is normal and can improve efficiency at typical operating conditions, but significant undersizing clips output on sunny days.
- Efficiency (rendement): the percentage of DC input converted to AC output. Modern quality inverters are 96-98%. Below 95% is worth querying.
- Number of MPPTs: MPPT stands for Maximum Power Point Tracker. Multiple MPPTs allow the inverter to handle different roof orientations or shading zones independently. A south-facing single-pitch roof needs one MPPT. An east-west split roof needs two.
- Monitoring: most modern inverters include WiFi connectivity and an app for monitoring daily and lifetime production. Useful for spotting drops in performance early.
- Warranty: inverter warranties are typically 5 years standard, with extended warranties of 10-12 years available from reputable brands. Given that the inverter is the most likely component to need replacement, the warranty length matters more here than for the panels.
How long does an inverter last?
Solar panels are typically warranted for 25-30 years and have a long service life. Inverters typically last 10-15 years under normal conditions, so a system installed today will likely need at least one inverter replacement over its lifetime. This is a planned cost, not a failure: factor it into any long-term ROI calculation. The replacement is straightforward for a string inverter; microinverters have a higher per-unit replacement cost but the failure of one doesn't take down the whole array.
Grid certification requirements in France
Any inverter connected to the Enedis distribution grid must meet French grid connection standards and be approved for anti-islanding protection: it automatically disconnects from the grid if the grid supply fails, protecting maintenance workers. Your installer handles the technical compliance and the Enedis connection request, but it's worth knowing that the inverter brand and model listed on your quote is checked as part of that process. Reputable European and Japanese brands (SMA, Fronius, SolarEdge, Enphase) have established French approval pathways; less familiar brands may create complications.