Grid-tied inverters include conventional low-frequency transformer-coupled types, newer high-frequency types, also transformer-coupled, and transformerless types.[3]​ Instead of converting direct current directly into AC suitable for the grid, high-frequency types of transformers use a computer process to convert power to high frequency and then back to DC and then to the final AC output voltage suitable for the grid.[4]​[5]​.

Transformerless inverters, which are popular in Europe, are lighter, smaller and more efficient than transformer inverters. But transformerless inverters have been slow to enter the US market due to concerns that transformerless inverters, which have no galvanic isolation between the DC side and the grid, could inject dangerous DC voltages and currents into the grid under fault conditions.[6]​.

However, since 2005, the NFPA NEC allows transformerless or non-galvanically isolated inverters by eliminating the requirement that all solar electrical systems be negatively grounded and specifying new safety requirements. The amendments to VDE 0126-1-1 and IEC 6210 define the design and procedures required for such systems: primarily ground current measurement and DC-to-grid isolation testing.

The technical sheets of the manufacturers of their inverters usually include the following information:

Grid-tied inverters include conventional low-frequency transformer-coupled types, newer high-frequency types, also transformer-coupled, and transformerless types.[3]​ Instead of converting direct current directly into AC suitable for the grid, high-frequency types of transformers use a computer process to convert power to high frequency and then back to DC and then to the final AC output voltage suitable for the grid.[4]​[5]​.

Transformerless inverters, which are popular in Europe, are lighter, smaller and more efficient than transformer inverters. But transformerless inverters have been slow to enter the US market due to concerns that transformerless inverters, which have no galvanic isolation between the DC side and the grid, could inject dangerous DC voltages and currents into the grid under fault conditions.[6]​.

However, since 2005, the NFPA NEC allows transformerless or non-galvanically isolated inverters by eliminating the requirement that all solar electrical systems be negatively grounded and specifying new safety requirements. The amendments to VDE 0126-1-1 and IEC 6210 define the design and procedures required for such systems: primarily ground current measurement and DC-to-grid isolation testing.

The technical sheets of the manufacturers of their inverters usually include the following information: