Do You Need An Inverter For Each Solar Panel?

An inverter is a critical component of solar photovoltaic systems that converts the direct current (DC) electricity generated by solar panels into alternating current (AC) electricity that can be used to power homes and businesses. Without an inverter, the DC electricity produced by solar panels cannot be utilized by most electrical devices, appliances, and grids which require AC power (https://www.energy.gov/eere/solar/solar-integration-inverters-and-grid-services-basics).

Inverters serve as the interface between a solar array and the utility grid or stand-alone electrical network. They convert the DC power into usable AC power through a multistage power electronics process. In addition to this key DC to AC conversion function, inverters also provide critical monitoring, control, and protection capabilities to ensure safe and optimal system operation.

One Inverter Per Panel

A common misconception is that each panel needs its own inverter. In reality, it is not necessary or cost effective to have a separate inverter for every solar panel. While it is technically possible to install inverters for each panel, most residential and commercial solar systems use central/string inverters or microinverters to convert the direct current (DC) electricity from the solar array into usable alternating current (AC) power.

Having individual inverters for each solar panel would dramatically increase the system’s cost and complexity without providing significant advantages. Central inverters and microinverters are designed to combine and convert the DC output from multiple panels efficiently and effectively.

String Inverters

String inverters are designed to handle multiple solar panels connected in series, known as a string of panels. They convert the DC output from the entire string into AC current that can be used in your home or fed back into the grid. According to SolarReviews.com^[1], string inverters connect strings of panels in one central location and are best for simple installations.

With a string inverter, each panel is connected in series to form a string. Multiple strings can be connected to a single inverter. The inverter will combine the output of the entire string or strings into one AC output. String inverters are a cost-effective choice for smaller residential systems and allow for modular expansion as needed. They also take up less physical space than microinverters or power optimizers.

However, shading on just one panel in a string can bring down the performance of all panels connected to that inverter. String inverters offer limited panel-level monitoring and troubleshooting ability. Overall, they provide a simple and affordable solution when solar panels are arranged in an optimal unshaded array.

Microinverters

Microinverters allow each solar panel to have its own individual inverter mounted on the back. This means that if one panel is shaded or fails, the rest of the system can continue generating electricity uninterrupted. Microinverters also maximize energy harvest from each panel, as they perform MPPT on a per-panel basis. This enables them to get more power compared to string inverters, especially in complex rooftop setups with varied shading.

Some key benefits of microinverters include:

• Module-level monitoring – You can see how much each panel is producing.
• No single point of failure – Issues with one panel don’t affect the rest of the system.
• Better shade tolerance – Panels with shade can underperform without compromising the system.
• Easy to expand – Just add more panels and microinverters.

Microinverters are more expensive upfront than string inverters, but the optimized production and panel-level monitoring can make up for the added cost over the system lifetime. Overall they excel in complex roof situations and provide maximum flexibility for system expansion and panel-level control.[1]

Central Inverters

Central inverters are designed to convert the total DC output from multiple strings of solar panels into AC power. They are larger in size and rated for higher wattages than string inverters. According to SMA America (https://www.sma-america.com/products/solarinverters/sunny-central-up), their Sunny Central inverters can handle 4,600 kVA output for large-scale solar installations. Central inverters are commonly used for commercial and utility-scale systems where many solar panels are connected together.

The main advantage of central inverters is their high efficiency in converting large amounts of DC power to AC, as they are optimized for handling many inputs. They also require less maintenance than microinverters or string inverters since there are fewer overall units. However, if the central inverter fails, the whole system will go down. So redundancy is important for maximizing uptime.

Pros and Cons

When choosing which type of inverter to use, it’s important to compare the pros and cons of each option.

String inverters, which are connected to multiple solar panels, have some key benefits. They are simple to install and maintain, and provide good performance in arrays with consistent solar exposure. However, string inverters can cause energy loss if any panels are shaded or damaged. Overall power output is limited by the weakest panel. String inverters also don’t provide much visibility into the performance of individual panels (Green Ridge Solar).

Microinverters, attached to each solar panel individually, maximize energy harvest from each panel. They continue to operate even if one panel is shaded or damaged. Monitoring at the panel level provides excellent insights. However, microinverter systems have higher upfront costs for equipment and installation labor. They also require more maintenance with multiple smaller components (Solar.com).

Central inverters convert DC power to AC for the entire array. They provide economies of scale and are easy to maintain with just a single inverter. But central inverter systems see large power losses if any panels are underperforming. Granular monitoring is not possible, and expansion requires expensive equipment upgrades (AiRise Energy).

System Size Considerations

The inverter setup depends on the number of panels and system size.

For small residential systems with only a few solar panels, a single central inverter is usually sufficient. As a general guideline, central inverters can handle up to 20-30 solar panels depending on the power output of each panel. Going beyond this may require multiple central inverters or upgrading to a larger capacity inverter.[How Does Sizing A Solar Inverter Work?](https://www.energysage.com/solar/what-size-solar-inverter-do-i-need/)

For larger solar arrays, string inverters that handle a “string” of panels wired together may be a better option. String inverters are modular, so the system can be gradually expanded by adding more inverter units. Each string inverter can handle 10-20 panels. This setup is more efficient and flexible than central inverters for mid-sized and large systems.

Microinverters, which are dedicated to each panel, are well-suited to any size system. The modular nature makes it easy to expand over time. A potential downside is higher upfront cost for purchasing multiple microinverters.

When determining system size, make sure to account for future energy needs and potential system expansion. Oversizing the inverter capacity slightly allows room for growth.

Shading Considerations

One key advantage of microinverters is their ability to minimize power loss when solar panels are partially shaded. With a string inverter system, if one panel in the string is shaded, it can drag down the performance of all the other panels connected to that inverter. As this article explains, “If you have panels that will see partial shade throughout the day, you’ll definitely want to go with microinverters.”

Microinverters allow each solar panel to operate independently. So if one panel is shaded, the other panels can continue producing at full output. This makes microinverters ideal for roofs with obstacles that might cause shading like chimneys, vents, or trees. Overall, microinverters can maximize energy production from a solar system when partial shading is a factor.

Cost Comparison

The cost of inverters can vary significantly depending on the type and size of the solar system. Here is a comparison of inverter costs for different system sizes:

For a small 5 kW system, a microinverter system would cost around $5,750 (5 kW x $1.15 per watt), while a central inverter system would be around $3,750 (5 kW x $0.75 per watt). So microinverters have a higher upfront cost for small systems.

For a medium 10 kW system, a microinverter system costs approximately $11,500, while a central inverter system is about $7,500. The cost difference remains similar.

However, for a large commercial 100 kW system, a central inverter system may cost around $75,000, while a microinverter system could be $115,000 or more. So the cost premium for microinverters becomes more pronounced for larger solar arrays.

In general, microinverters cost 50-100% more per watt than central inverters. But microinverters can lead to higher energy production, so the return on investment timeframe may be acceptable, especially for smaller systems where the cost difference is lower.

Conclusion

When selecting an inverter for your solar panel system, there are a few key factors to consider. The size of your system and whether you anticipate any shading issues will help determine whether string inverters, microinverters, or central inverters are the best fit. While microinverters offer maximum optimization for shading, they also come at a higher upfront cost. String inverters provide a good middle ground if you have a medium to large system with minimal shading. For utility-scale solar farms, central inverters remain the standard choice.

In most residential installations, microinverters provide the best performance and easiest configuration at a reasonable cost premium over string inverters. The enhanced system monitoring and panel-level optimization of microinverters can result in good long-term value for homeowners. For larger commercial systems, string inverters are likely the better option based on lower cost and simpler installation. Regardless of inverter type, working with a reputable installer is key to ensure proper system design and configuration.