Solar panels produce DC electricity, so they need to be fed through an inverter to convert the power to AC electricity to be used in a grid-connected solar power system.
There are two main types of inverters:
Micro inverters (one inverter per panel) and…
string inverters (one inverter for many panels).
Neither inverter is ‘better’ than the other, the best choice for your solar PV system depends on your situation.
These are the main points to consider:
1. Because micro inverters effectively make each solar panel a mini-system, they are a good choice for situations where shading is a problem.
This is because only the panels that are in the shade are affected, rather than the whole solar array. This is no doubt an advantage, but remember solar panels shouldn't be installed in a position where they will be shaded unless it is unavoidable for a portion of the day.
2. Quality string inverters are a proven technology and are highly efficient.
Micro- inverters are a newer technology that hasn't been developed to the same extent.
3. String inverters are mounted near the meter-board out of the weather, and a quality inverter is extremely reliable.
Micro inverters are mounted directly to the panels, meaning they are subject to extreme weather conditions and a huge range of temperatures, which is much harder on the electronics. In the event of a failure, a string inverter is easier to replace as it does not require roof access. However a string inverter failure will bring down the whole system where a micro inverter failure will only affect the panel it is attached to.
4. The maximum power point varies depending on the amount of sunlight available.
Any manufacturing differences between the panels will also affect the maximum power point. A string inverter averages the maximum power point of the entire array, where micro inverters utilise the ‘maximum power point’ of each panel individually. For this reason, micro inverters can yield more energy in some situations. Micro inverters are ideal in situations where the panels will not all be receiving sunlight at the same time (different roofs, different angles etc.)
5. String inverters are usually about 40% cheaper than micro-inverters.