Why can't solar panels and inverters be matched in a 1:1 ratio?

What's the solar inverter DC/AC ratio?

It is the ratio of "total power of solar panels" to "rated output power of inverters", with the core function of "balancing power generation and equipment life", avoiding "big horses pulling small cars" or "small horses pulling big cars".

For example, if your roof is equipped with 12kW solar panels (the total power of all solar panels) and a 10kW inverter (the maximum power that the inverter can stably output), then the ratio of this system is 12 ÷ 10=1.2.

Why is the ratio mostly not 1:1? 

Many people may wonder, 'Isn't it just right for me to install 10kW solar panels and equip them with a 10kW inverter? ”In fact, it is not the case because the "rated power" of solar panels is the theoretical value under ideal laboratory conditions (25 ℃, 1000W/㎡ illumination), which cannot be achieved when actually installed on rooftops.

High temperature, dust obstruction, weak light in the morning and evening, cable loss, and even power attenuation after long-term use of components can all "discount" the actual output power of the components - for example, in summer, when the roof temperature rises to 60 ℃, the power of the components will directly decrease by 10% -15%; Accumulation of dust on a regular basis can result in a loss of approximately 5% of power. By calculation, the actual power that inverters can receive is often only 70% -85% of the rated power of the components.

If the ratio is selected as 1:1 (10kW module with 10kW inverter), it is equivalent to the inverter being "hungry" all year round and operating at low load for most of the time, wasting the capacity of the inverter in vain; Reasonably increasing the capacity ratio (such as 1.2-1.3) can fill this "power gap", allowing the inverter to operate at full load most of the time, which is equivalent to "draining" the power generation capacity of the solar panels, while also controlling system costs.

Sunlight resources are the core basis for selecting the ratio, and the ratio varies greatly in different sunlight regions.

-In areas with sufficient sunlight (annual sunshine hours ≥ 3000 hours, such as the northwest and Qinghai Tibet Plateau), the capacity ratio is 1.1-1.2 to avoid frequent overloading of the inverter due to excessive capacity ratio. Long term high-temperature operation will accelerate the aging of the inverter core components and shorten their service life;

-In areas with average sunshine hours (1500-3000 hours per year, such as East China, Central China, and North China), the capacity ratio is 1.2-1.5, which balances power generation and equipment safety, and is recognized as the "golden ratio" in the industry;

-In areas with insufficient sunlight (annual sunshine hours ≤ 1500 hours, such as Sichuan, Guizhou, and Chongqing), the capacity ratio is 1.5-1.8. For example, an 18kW component is equipped with a 10kW inverter. Even if the actual peak output of the component is only 10kW, it can be fully converted to the grid by the inverter, maximizing the utilization of limited sunlight resources.