What is an inverter?

​An inverter is a crucial component of a solar PV system. They're responsible for converting the DC electricity generated by solar panels into AC electricity used by your household appliances. Inverters also optimise power output, ensure system safety and communication with the grid. There are several types of inverters, each designed to suit different system configurations and user needs:

1. String Inverters

String inverters connect multiple solar panels to form a "string" and the combined DC electricity is fed into a single inverter that converts it to AC. This centralised approach is cost-effective and straightforward to install. However, the performance of the entire string can be affected if one panel underperforms due to shading or damage, as the system operates at the level of the weakest panel. Most importantly, string inverters only invert solar panel power, and don't support any batteries.

2. Battery inverters or 'AC-Controllers'

A battery inverter is very similar to the above string inverter, but for the batteries only. Solar panels generate energy in DC, and need in changing into AC energy. Similarly, batteries store energy in DC and need it inverting to AC to use in your home. This is the job of an AC-controller, or battery inverter. When installing a dedicated battery inverter, (typically alongside a string inverter), this is known as an 'AC-coupled system'. This is typically found in systems where batteries have been retro-fitted, or where the home has a feed-in-tariff, and the battery system needs installing to not jeopardise this fruitious tariff.

3. Hybrid Inverters

Hybrid inverters are essentially a string inverter, and AC-controller all in one. They're typically found in installations where panels and batteries have been installed simultaneously. Any surplus made DC energy is routed straight to the battery without any inversion, which makes this DC-coupled system more efficient. This integration simplifies the system design and can be more efficient than adding a separate battery inverter later. Hybrid inverters are also sometimes installed for new installations where future battery storage is anticipated.

4. DC-Coupled Inverters

In DC-coupled systems, the solar panels and battery storage are connected to a single hybrid inverter. The DC electricity generated by the panels can directly charge the batteries without multiple conversions, improving overall system efficiency. When energy is needed, the inverter converts the stored DC electricity to AC for household use. DC-coupled systems are typically more efficient than AC-coupled ones but may be less flexible for retrofitting batteries to existing systems. ​

5. Micro-inverters

Micro-inverters are small inverters attached to each individual solar panel, allowing for independent operation of each panel. This design mitigates the impact of shading or malfunctions on a single panel, as each micro-inverter operates independently. Micro-inverters enable panel-level monitoring and can increase overall system performance when shading is present. It's worth nothing that they are generally more expensive than string inverters.

Maintenance of micro-inverters is very important. Whilst they are typically provided with a long manufacturer guarantee, replacement of them (should they fail due to a manufacturing fault), is often not covered by a workmanship guarantee. Scaffolding/safe access may be required to remedy any issues. Due to this, when Creative Low Carbon installers fit a micro-inverter system, we advise installing the micro-inverters inside the roof, rather than outside, directly under the panel. This will drastically lower any remedial visit cost.

Micro-inverters vs. Power Optimisers

While micro-inverters convert DC to AC at each panel, power optimisers (such as "Tigos") are devices attached to individual panels that condition the DC electricity before sending it to a centralised inverter- imagine it as parallel style wiring. Power optimisers can improve the performance of each panel in shading conditions, and allow for panel-level monitoring. However, the actual inversion from DC to AC occurs at a central inverter rather than at each panel. This setup can be more cost-effective than micro-inverters while still offering many of the same benefits.

Choosing the right inverter depends on various factors, including system size, budget, shading conditions, and future plans for battery storage. Consulting with Creative Low Carbon can help determine the most suitable inverter type for your specific needs.