What is the DC:AC Ratio?

You may notice that your Solar Panels are rated at a higher wattage than your Micro-Inverters.

This is completely normal and this is known as the DC:AC Ratio.

A DC:AC ratio of between 1:1 – 1:4 is recommended for best performance in the UK (dependent on factors such as location, angle of inclination, orientation and shading).

For example, 1,000W (1kW) of Solar PV Panels, connected to an 800W Micro-Inverter, will give you a DC:AC Ratio of 1:25. 1,000 ÷ 800 = 1.25.

In short, having a good DC:AC Ratio means that in low light conditions (which are far more common in the UK than peak conditions) a smaller rated Micro-Inverter linked to a larger wattage Solar Panel results in your system starting to produce energy earlier in the day and later into the evening. 

This is due to the fact the start up voltage of the Micro-Inverter will be met more quickly.  This is also the case on overcast and cloudy days when the startup voltage will be met more quickly.  

Although your panels will be clipped at the very top end of performance, in the UK solar panels rarely produce power at the rated output due to sun angle, time of year as well as environmental, electrical, cabling and thermal losses.  Panel degradation over time also is taken into account (2% for the first year and 0.4% each year after that).

DC:AC Ratio matching is common practice in Solar PV systems to enable you to achieve the best results from the system over the lifetime of the system, not just in peak conditions.