What Is a Microinverter? Microinverter or String Inverter?

Microinverters and string inverters convert the direct current generated by solar panels into usable alternating current; the difference lies in where this conversion takes place and how many panels it serves. The right choice depends not only on the price of the device, but also on roof orientation, shading, panel count, monitoring expectations, and future energy storage plans.

What Is a Microinverter and How Does It Work?

A microinverter is a small power converter installed behind or near a solar panel. It converts the DC electricity from the panel into AC electricity on the roof. A microinverter may manage a single panel or provide inputs for multiple panels, depending on the product design.

Independent maximum power point tracking (MPPT) for each input or panel helps panels under different irradiance conditions affect one another less. For example, if one panel is shaded by a chimney in the morning while another receives sunlight, the independent MPPT architecture helps the sunlit panel continue producing at its own operating point.

The TommaTech Micro S 800W Single-Phase Inverter in CW Enerji's verified product range is an example of a microinverter for small-scale applications, with two independent MPPTs, two string inputs, remote monitoring, an IP67 protection rating, and single-phase AC output. Technical suitability must also be verified against the electrical values of the connected panel and the project conditions.

What Is a String Inverter and How Does It Work?

In a string inverter architecture, multiple panels are connected in series to form a panel array, or “string.” DC electricity from the string is converted into AC electricity by a central inverter. Depending on the inverter's number of MPPTs and input configuration, multiple strings can be managed separately.

Panels facing the same direction, with similar tilt and shading conditions, can operate efficiently with a correctly designed string. Locating the inverter in an accessible technical area can make inspections and servicing easier. However, if panels within the same string differ in shading, soiling, orientation, or electrical characteristics, the string's behavior may be affected by this mismatch.

CW Enerji's on-grid inverter product range includes single-phase and three-phase string inverter options at different power levels. In addition to system power, the MPPT operating range, maximum input current, string voltage, phase configuration, protection features, and monitoring capabilities are all part of the selection process.

Differences Between Microinverters and String Inverters

Is a Microinverter Always Better Under Shading?

No inverter can recover the solar energy lost by a shaded panel. The advantage of a microinverter is its ability to limit the impact at panel or input level. If shade caused by a tree, chimney, antenna, parapet, or neighboring building moves throughout the day, independent operating points can help preserve the output of the other panels.

However, the conclusion that “a microinverter will definitely generate more whenever there is shade” is not correct for every project. The IEA PVPS study on partial shading states that results depend on the shape of the shade, system topology, and the power electronics' own losses, and that conventional string inverters can also perform strongly in some scenarios. The decision should therefore be based on an annual shade analysis and comparative production simulation.

What Is Examined in a Shade Analysis?

• During which months of the year and hours of the day the shade occurs
• Whether it affects a single cell, part of a panel, or the entire panel
• How many different orientations and tilt angles will be used for the panels
• The number of independent MPPTs and string layout available with a string inverter
• Compatibility of the microinverter with the panel's voltage, current, and power values
• Estimated annual production and total cost of ownership for both architectures

Should You Choose a Microinverter or a String Inverter?

The U.S. Department of Energy's explanation of inverter technologies states that, with microinverters, shade or damage to one panel does not affect the power that can be drawn from the others, but microinverters may be more expensive. The same institution's PV system design guide notes that a central inverter may be easier to service and cool.

A Third Option: Power Optimizers

A power optimizer performs DC-to-DC conversion and MPPT at panel level, while the final DC-to-AC conversion takes place in a central string inverter. It therefore combines some features of panel-level management and a central inverter architecture. However, the additional component, compatibility, efficiency loss, monitoring infrastructure, and cost must still be evaluated for each project. An optimizer does not eliminate shade either; it only changes how the system responds to shading.

Which Technical Values Should Be Checked When Choosing a Microinverter?

Looking only at the inverter's watt rating is not enough. Panel and inverter matching must be based on electrical calculations that also cover the coldest and hottest operating conditions.

• Permitted maximum DC input voltage and MPPT operating range
• Maximum short-circuit and operating current for each input
• Number of panels that can be connected and recommended DC/AC power ratio
• Compatibility with single-phase or three-phase grid configurations
• Permitted number of devices per AC branch and cable cross-section
• Protection rating, operating temperature, and mounting conditions
• Gateway or communication infrastructure required for remote monitoring
• Scope of the product and performance warranties
• Grid connection, protection, and project requirements

A grid-connected microinverter system does not automatically become suitable for every electrical installation simply because the device is described as “plug and play.” Panelboard capacity, grounding, residual-current and overcurrent protection, cable cross-section, connection point, and applicable distribution requirements must be verified by qualified professionals. The device should not be connected directly to the existing installation before it has been assessed.

Can a Microinverter Be Used with a Battery?

Because a microinverter produces AC output at the panel, storage integration is generally considered through an AC-coupled architecture. Interoperability among the battery inverter, energy management system, and microinverter must be verified through product documentation. Communication, charge-discharge control, grid disconnection, and backup-load behavior are part of the design.

For a new system in which the battery is the priority, a hybrid string inverter and DC-coupled storage may be a simpler option. When adding a battery later to an existing AC solar system, a compatible AC-coupled solution can be considered. CW Enerji's energy storage solutions offer different residential architectures; the correct capacity and connection type should be selected according to the consumption profile and backup expectations.

8 Questions to Ask the Project Team Before Deciding

1. Which data and method were used for the annual shade analysis?
2. Were the estimated annual outputs of the microinverter and string inverter options compared?
3. How many different orientations and tilt angles will the panels have?
4. Are the voltage, current, and power values of the inverter and panel compatible?
5. Will monitoring be performed at panel level or string level?
6. How will roof access and replacement be managed in the event of a fault?
7. What limits will apply if panels or a battery are added in the future?
8. Does the proposal include protection equipment, engineering, commissioning, and warranty?