How to choose the power of the inverter to the power of the panels?

Any photovoltaic installation, in order to fulfill its primary function of being a source of free electricity, must have an inverter in its circuit, which will turn the direct current (DC) produced in the panels into alternating current (AC) that powers our households. While the selection of the panels themselves usually goes fairly smoothly, the question of matching the inverter with the rest of the installation can be a bit tricky. So how to perfectly match the inverter to the power of the installation and what to pay attention to when doing so, and why is too much and too little inverter power just as bad?

Did you think that panel power equals inverter power? Well, this is a fairly common, albeit misconception, because these values are absolutely not the same, primarily because panel power is defined as the maximum generating power under standardized, and therefore controlled and repeatable, test conditions. Thus, since under natural conditions the panels operate at different wattages depending on the weather and time of day, it is particularly important to maximize their efficiency by selecting the appropriate inverter power. Manufacturers recommend completing the set in such a way that the power of the panels is between 80-125% of the maximum power of the inverter, but the best results are achieved when the power values are between 105-120%. Selecting the panels in this way to the power of the inverter is called oversizing.

The power of the inverter is closely related to its maximum capacity to process current from the panels. More precisely – the efficiency of the inverter is greater, the smaller the difference between its maximum power and the power of processed energy. Thus, the processing capacity of any inverter has an upper limit, but it is simply more cost-effective to operate at the permissible highest speeds due to the price of these devices. And while it would be tempting to preemptively use a higher-power inverter, which could theoretically convert larger amounts of energy in our favor when conditions are favorable, in practice, the larger the inverter, the less we will use its potential in a situation of limited solar exposure. Choosing an inverter with too much power relative to the panels used will therefore be an inappropriate solution in the sense that the expenses incurred for the device will not be offset by the level of yields compared to the maximum capabilities of the device.

On the one hand, the smaller the inverter, the easier it is, even despite the passage of time and the decline in the performance of the panels themselves, to achieve satisfactory performance of the installation, because the device will operate within the limits of maximum performance for a long time. But what happens if the amount of energy produced exceeds many times the power of the inverter installed in the circuit?

The principle of appropriate oversizing of the panels relative to the power of the inverter is important, because if the power of the inverter relative to the power of the panels is too small, so the oversizing will reach above the recommended 125%, then as the intensity of operation of the panels increases, the coefficient of energy loss will grow. This happens when the inverter is simply unable to convert the energy generated through the photovoltaic phenomenon, and although it is produced intensively, but it does not flow into the grid at the same level, and the unabsorbed energy is lost in the panel itself.

Under certain circumstances, it is worth sacrificing a little energy and letting it be lost on the days when the panels will be working most intensively during the year, in order to achieve, at this cost, more efficient operation of the installation when the sun will be scarce.

We do not hide the fact that, despite the seemingly simple principle of calculation, it is a difficult task to achieve the ideal balance of losses during a solar boom and maximizing yields during a downturn. So if you are not sure whether your calculations correspond to reality, or if you feel that photovoltaics are not your thing, it is our job to make sure that you go through the entire process of buying the installation successfully and with the right support – from the selection of the power of both panels and inverter to the subsequent after-sales service.