Solar inverter (grid-tied PV inverter)

01

Compare weighted efficiency, not peak efficiency

Sandia's description of the California Energy Commission (CEC) inverter test protocol says efficiency is measured at six power levels (10, 20, 30, 50, 75 and 100% of rated AC power) and three DC voltages (minimum, nominal and maximum), and a weighted average is formed with weights of 0.04, 0.05, 0.12, 0.21, 0.53 and 0.05 respectively, which do not change with DC voltage. [1] DNV's SolarFarmer documentation gives the European weighting as 0.03 at 5%, 0.06 at 10%, 0.13 at 20%, 0.10 at 30%, 0.48 at 50% and 0.20 at 100% load, and explains both are intended to reflect each region's likely operating regime. [2]

Solis's datasheet for its S6-GR1P 2.5–6 kW single-phase inverters lists maximum efficiency of 97.3–97.7% and EU efficiency of 96.5–97.1% across the range, a transformerless topology, night self-consumption under 1 W, and a power factor above 0.99 adjustable from 0.8 leading to 0.8 lagging with current THD under 3%. [3]

Editorial note: because the European weighting gives 0.03 and 0.06 to 5% and 10% loads while CEC starts at 10%, the two figures are not interchangeable; compare inverters on the same weighting and, where possible, at the DC voltage your strings will actually run at, since the CEC protocol measures at three voltages. [1] [2]

Give the supplier the site's grid connection (single or three phase, voltage, frequency, applicable grid code), PV array design (module model, Voc and temperature coefficient, modules per string, strings per MPPT), lowest and highest site temperatures, required AC power and DC/AC ratio, export limits, battery or backup needs, monitoring and communication, enclosure and cooling conditions, and certifications required.

02

Size strings to the DC voltage and MPPT window

The Solis S6-GR1P datasheet lists a maximum input voltage of 550 V, rated input voltage of 250 or 330 V, start-up voltage of 60 or 100 V and an MPPT range of 50–550 V or 90–550 V depending on model, two MPPTs each with one string, 16 A maximum input current and 22 A maximum short-circuit current per MPPT, and recommended maximum PV power from 3.75 kW for the 2.5 kW model to 9 kW for the 6 kW model. [3]

Editorial calculation: the recommended PV power is 150% of rated AC output (3.75 / 2.5 kW), a DC/AC ratio of 1.5. For an assumed module with 49.5 V open-circuit voltage at 25 °C and a −0.27%/°C coefficient, the open-circuit voltage at −10 °C is about 49.5 × (1 + 0.0027 × 35) ≈ 54.2 V, so ten modules reach about 542 V — inside 550 V — while eleven would reach about 596 V and exceed it. Use your module's datasheet values and the record low temperature. [3]

The datasheet also lists IP66, −25 to +60 °C operating ambient, operation to 4,000 m, an integrated DC switch, anti-islanding, surge and reverse-polarity protection, optional AFCI, and grid-connection approvals including EN 50549-1, VDE-AR-N 4105, CEI 0-21, IEC 62116 and IEC 61727, with IEC/EN 62109-1/-2 safety. [3] Editorial note: approvals are market-specific; confirm the certificate for your country's grid code.

For comparison with installed practice, a 2025 dataset paper in Scientific Data by Stid and co-authors, harmonising US ground-mounted solar records, uses a median inverter loading ratio (DC to AC) of 1.3 taken from the US Large-Scale Solar Photovoltaic Database when converting AC capacity to DC, and cites industry figures of about 220 GW DC of US solar installed by the third quarter of 2024, around 70% of it utility-scale. [4] Editorial calculation: the Solis datasheet's recommended 150% PV power (a ratio of 1.5) is above that 1.3 median, so a 1.5 array spends more hours held at the inverter output limit; at 1.3, a 5 kW inverter would take about 6.5 kWp of modules against 7.5 kWp at 1.5. Ask the supplier for its allowed maximum DC power, not only the recommended figure, and model the clipping for your site. [4] [3]

03

Compare what suppliers offer

Suppliers linked to this page list solar inverters; each card links to the page reviewed.

Listings include residential and commercial string inverters, hybrid and energy-storage inverters, on-grid inverters with charge controllers, bidirectional home-energy inverters and PV inverters from power-electronics groups; ask each for datasheets with weighted efficiency, DC limits, MPPT count and grid certificates.

04

Trace the inverter parts

This is a functional reference built from the sources cited; it is not one maker's specification.

05

Fill the specification fields with values for your system

A solar inverter quotation needs values for your system. The table explains each field, gives published values where a reviewed source states them, and says what to obtain from the supplier.

06

Send the grid, array and site data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Grid: [phases; voltage; frequency; grid code; export limit]
Array: [module model; Voc; temperature coefficient; modules per string; strings]
Site: [record low and high temperature; altitude; indoor or outdoor]
Inverter: [AC power; DC/AC ratio; MPPT count; hybrid or not]
Efficiency: [CEC or EU weighted]
Monitoring: [interface; platform]
Documents: [datasheet; grid certificates; warranty]

See manufacturer records Send an enquiry through CNFX