By Susanna Huang, Ginlong USA
My answer might be a long one. Both inverters need to convert DC to AC. The difference is where this occurs. Micro-inverters convert DC to AC at the back of each solar panel on the roof, while string inverters do it on the ground at the string level. Let’s look at the pros and cons of each inverter type, from my point of view.
Production
For a house with a complex roof and shading or soiling concerns, micro-inverters tend to work better due to their panel-level optimization. However, for a houses with a simple roof and good orientation, string inverters can do a good job due to their high efficiency. The latest string inverters are equipped with dual MPPT technology. The production is improved as the solar inverter is capable of connecting two unbalanced string with different orientations.
Initial Cost
Micro-inverters usually have higher initial equipment cost than string inverters. One of the most popular micro-inverters is sold at about $0.7/W with a 25-year warranty. String inverters are sold at about one third of that cost with a 10-year warranty.
Maintenance
Micro-inverters are known for their low individual failure rate, probability as they carry low AC voltage. But a, say, 5-kW solar system may have 23 micro-inverters and the failure rate increases with number of items in a system. When a micro-inverter fails, someone has to climb to the roof, remove panels and install a new one. Since a string inverter is mounted on the wall, workers need not climb the roof to fix it.
I have found that decision makers in different solar markets have their own preferences.
Solar leasing companies lean toward string inverters. They are the owner of the solar system and so cautious about who to work with and which solar equipment to use. They like to work with manufacturers with proven track record and mature inverter technologies with high efficiency.
Micro-inverters have become popular among home owners who are attracted by the latest technology, panel-level optimization and good monitoring functions.
In the end it’s up to the solar contractor to provide the customer with a professional opinion, recommending the best solution based on the customer’s unique situation.
By Susanna Huang, Ginlong USA
This article was originally published in Susanna’ Huang’s blog at susannahq.wordpress.com