Inverter oversizing

Written and checked by the Energy Merchants desk · Reviewed 3 October 2026

Inverter oversizing is when the solar array is larger than the inverter. A 6.6 kW array on a 5 kW inverter has a DC to AC ratio of 1.32, or 132%. It is a common and deliberate design choice, not a mistake.

Why it works

Panels seldom produce their full rated output. Heat, angle and cloud mean most days a 6.6 kW array delivers well below 6.6 kW, so a 5 kW inverter is rarely overloaded. On the best days the inverter clips the peak, and the small loss is outweighed by more energy captured in the morning and evening. Guidelines from the Clean Energy Council have commonly allowed ratios of up to about 133%, although limits depend on the inverter manufacturer and the network.

In practice

Networks often cap the inverter’s AC rating, for example by limiting inverter size per phase or by setting an export limit. Oversizing the panels is the standard response: the customer keeps a larger array for self-use while the connection stays within the network’s rules. Always check the inverter’s datasheet for the maximum DC input.

How STCs are affected

STCs are deemed on the rated output of the panels, with the zone and the deeming period, not on the inverter. So an oversized array creates more STCs than a matched one. A 6.6 kW array in zone 3 installed in 2026 creates 6.6 x 1.382 x 5 = 45 STCs, regardless of the inverter. See zone rating and the STC calculator.

Common confusion

Oversizing is not the same as overloading. The inverter is not asked to push more than its rating. It is also separate from the rule that STCs are for panels that meet the approved product requirements. A panel not on the approved list creates nothing.

See also DNSP, STC trading and the glossary.