The purpose of both micro inverters and string inverters is to convert the Direct Current (DC) generated by solar panels into an Alternating Current (AC) as the latter type of current is used in our homes.
What is meant by a string inverter?
A string inverter is also known as the standard inverter or central inverter and is a standalone box that is installed close to the electricity meter and fuse box. Each residential solar installation usually has one or may be two string inverters. It functions in a series circuit and the number of individual solar panels is usually 6 to 10 and this is what is called the “string.”
How is a micro inverter different from a string inverter?
A micro inverter works in a parallel circuit. A string inverter will cap the production of electricity of each panel by the lowest producing one. But in case of micro inverters full advantage of the production of every individual panel is taken. It will transform the power generated by each panel to the grid voltage.
Micro inverters perform the same basic function like the string inverter. But these are installed beneath every panel on the roof. Every micro inverter is almost the size of an internet router. The greatest difference is that in case of installation with micro inverters the number of micro inverters needed is equal to the number of solar panels.
What are the advantages of string inverters?
The advantages of string inverters are enumerated below –
- The economy is an advantage as in case solar panel installation of single string inverter the cost is usually less than installing micro inverters.
- You need only one string inverter. In the case of solar panel installations, if anything fails it is the inverter. As such it would be less likely that you will have to go back to a job if you are an installer.
What are the disadvantages of string inverters?
In the case of string inverters, the solar panels need to be wired in series. So if the output of one solar panel is adversely affected the total series is affected equally. This can become a major issue if a part of the solar panel system remains in shade for a part of the day.
What are the advantages of microinverters?
The advantages of microinverters are –
- If your solar system faces multiple angles which means that some panels are facing east, some south, and some west, then microinverters are the best solution.Again if there are shading issues like a big chimney or trees, microinverters are ideal. This is because in such conditions, the solar panels producing various amounts of electricity at different times of the day, with micro inverters you will harvest all of the energy. But you will lose some production with string inverters. Only if all the solar panels are facing the same direction and the shading issues are minimal, string inverter can be your option. This is because the production will be the same at less cost.
- Microinverter usually has a 25-year warranty while string inverters have 5 or 10-year warranties. The technology has advanced so much that the question of reliability of micro-inverters has decreased. Also, big warranties have made them more attractive.
- The main advantage is you can yield more solar electricity. This is because there are few voltage differences between solar panels. But if the solar panels are in a string, the voltage is decreased to the voltage of the lowest voltage panel in the string.
- Optimizers are options for both string inverters and micro inverters. With an optimizer, you have a standard inverter. But you also have optimizers for every panel fighting the differences in production.
- Microinverters and the add-on optimizers enable you to track the production of every individual panel. But with string inverters, you are able to track the production of the total system only.
- Again if you wish to expand your system later, it is easy to add micro-inverters one at a time. But with string inverters, the cost will escalate for addition of another full unit.
What are the disadvantages of micro inverters?
The disadvantages of micro inverters are –
- You will have as many inverters on your roof as the number of solar panels.
- The price is huge. It is usually $1,000 or more expensive as compared to string inverters in a normal 5kW residential solar installation.
In the solar system, the most complex electronics is the inverter. And this is the most likely thing to fail in the entire setup. So setting up 20 inverters can be an issue and as such string inverters score better unless there are severe shading issues.
In the case of microinverters, each panel can be monitored but the customer is not allowed to do the monitoring. The installer is allowed to see the panel level data from your system and not the customer unless you are agreeing to buy a higher level of monitoring as an upgrade. It is really quite difficult to find out if one or two inverters of the approximately 25 have failed with only system-wide monitoring data.
However, micro inverters have their benefits. Just be ready to pay the extra money for the level of monitoring that can give you panel level analysis. Also when a string inverter fails, the entire system will stop working.
So micro inverters are only a plus if your panels face different orientations or there are shading issues. If not, the less costly string inverter scores over the microinverter.