Guides

DC/AC ratio and inverter clipping

Published 8 October 2026. About 6 minutes to read.

It is normal for a solar array's panel rating to be larger than the inverter's AC rating. A 6.4 kWp array on a 5 kW inverter is a common, sensible design. The ratio between them is the DC/AC ratio, and getting it right is a balance between cost and lost energy.

Why arrays are oversized

Panels are rated at standard test conditions: 1,000 W/m² of sunlight and 25 °C cells. On a real roof they rarely reach that. Heat, dust, wiring losses, the angle of the sun and haze mean a panel spends most of its life well below its rating. An inverter sized to the full panel rating would rarely run near its capacity.

Adding more panels lets the inverter run closer to full output for more of the day, especially in the morning, late afternoon and winter, which is when a correctly sized array produces the least.

What clipping is

When the array could produce more than the inverter can deliver, the inverter limits its output by moving the operating point away from maximum power. The energy above the inverter's limit is lost. On a production curve it looks like the top of a sunny day's curve has been cut flat.

At moderate ratios this happens only for a few hours around noon on the clearest days, so the energy lost is small, often around 1 to 3 % of the year's production at a ratio of about 1.2 to 1.3. The extra energy gained in the rest of the day is usually much larger.

Typical ratios

• Around 1.0 to 1.1: little or no clipping, but the inverter is underused much of the time.
• Around 1.2 to 1.3: a common choice for equator-facing arrays.
• Up to 1.5 or more: can make sense for east-west arrays, which never peak at the same time, or where the inverter is expensive compared with panels.

Hot, very sunny sites clip more at a given ratio than cool or cloudy ones.

Check the inverter's limits

Every inverter datasheet gives a maximum PV input power, often 130 to 200 % of the AC rating. Going over it can void the warranty, so it is a hard limit, not a guideline. The voltage and current limits of each MPPT input still apply as well: more panels in series raises the voltage, and more strings in parallel raises the current. Battery inverters can also send surplus to the battery while the AC output is at its limit, which reduces clipping.

Checking the ratio in Lekker Sun

On the Equipment page, the compatibility check compares the array's total panel rating with the inverter's maximum PV input power and shows the DC/AC ratio, next to the string voltage and MPPT current checks. Change the number of panels in series or strings per MPPT and the checks update straight away.

This guide is general information to help you plan and compare options. It is not engineering, electrical or financial advice. Always follow the equipment manufacturer's instructions and your local wiring rules, and have a qualified installer check the design.