Power optimizer

Power optimisers are module-level power electronics (MLPE) that sit between each module and a central string inverter. Each optimiser runs its own MPPT and adjusts its output voltage and current so that a weak or shaded module no longer forces the rest of the string to its current. The inverter then only inverts DC to AC, often at a fixed, optimised string voltage.

SolarEdge built the dominant fixed-voltage system; Tigo, Huawei and others offer optimisers that work with third-party inverters, sometimes only on selected modules that are shaded.

• Peak conversion efficiency: up to about 99.5%; weighted about 98.8%.
• Recovered energy: from near zero on unshaded uniform arrays to 5–25% on roofs with chimney, tree or dormer shading, depending on shading pattern.
• Allow longer, uneven strings and modules on different roof faces on the same input.
• Provide module-level monitoring and safe-voltage shutdown (about 1 V per optimiser) for firefighter safety.

Compared with microinverters, optimiser systems keep a single inverter, which is usually cheaper and easier to pair with batteries, but they still have a central component with a 12–25 year warranty and many electronic parts on the roof. Optimisers do not remove the need for bypass diodes inside the module.