Until recently, every investor planning to install a photovoltaic installation had to know exactly their energy needs. On its basis, the optimal power of the photovoltaic installation was calculated. However, after the introduction of new regulations, it is difficult to talk about such a thing as an oversized PV system. Selecting modules should therefore be much easier than before. If you are designing a photovoltaic installation, be sure to read our guide!
From this article you will learn:
- how to select the power of a photovoltaic installation,
- how to adjust the power of photovoltaic panels to the building,
- what power of photovoltaic panels is most profitable.
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How to determine the power of a photovoltaic installation?
To correctly calculate the power of a photovoltaic installation, you must first specify which value it actually means. Theoretically, it is the product of voltage and current generated by photovoltaic panels, expressed in watts. However, there are significant differences between the nominal (maximum) power and the actual power.
The nominal power is achieved by photovoltaic modules under test conditions. For this reason, it is also called maximum and is expressed in watts (peak watts). In fact, this value is only achieved for short periods of the year.
The power that a photovoltaic generator can produce depends strictly on the conditions occurring in a given installation , and therefore primarily on:
- radiation level,
- sunny hours,
- module exposure
- and temperature.
The key parameter in the context of the correct selection of a PV installation is the amount of electricity that the installation is able to produce in a given unit of time. The higher this value, the more electricity is available to the household.
It should therefore be borne in mind that the building's annual electricity demand may be underestimated compared to the nominal power of photovoltaic panels provided by manufacturers. It is worth sticking to the assumption that in Polish climatic conditions, 1 kWp of the installation's power will produce approximately 1,000 kWh of electricity annually.
How to choose the power of photovoltaic panels for a single-family house?
In order to select the appropriate power of a photovoltaic installation for a building, it is necessary to determine the electricity consumption of its inhabitants. Electricity bills can only be reduced to zero when photovoltaic panels cover one hundred percent of the household's needs. As you already know, the minimum installation power is very easy to estimate.
All you need to know is your household's annual electricity consumption [kWh]. Thanks to it, you will quickly determine the power of photovoltaic panels [kWp] that the investor needs. Remember to add any additional demand to the result if the prosumer plans to buy, for example, an electric car or a heat pump in the near future. If such solutions appear at home a little later, it is worth designing the installation so that it can be easily enlarged in the future. For this purpose, a larger inverter and optimizers or micro-inverters can be used.
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Due to the current system of settling prosumers for energy surpluses, determining the minimum installation power makes little sense, which we will write more about in the last part of the article. In the new settlement system - netbilling - it can be assumed that the greater the power, the better. The regulations provide for the possibility of resale of the electricity produced to the operator. However, they also impose an energy limit for which the prosumer will receive a monetary refund. For this reason, one may be tempted to calculate the maximum reasonable power of the installation, with the proviso that no investor who decides to install photovoltaic panels on the roof is likely to achieve this value.
To estimate it, you can use the formula:
Installation power [kWp] = (Z x A + ((120% x Z x N) / (Ck / Cs))) / P
Its further components are:
- Z - annual energy consumption [kWh],
- A - auto consumption (%),
- N - surplus (%),
- Ck - average purchase price of electricity [PLN],
- Cs - average electricity sales price [PLN],
- P - annual electricity production from 1 kWp at the installation site [kWh].
Before making preliminary estimates, you should find out what the annual energy consumption is in your home, and also assume how much electricity will be used on an ongoing basis (A) and how much will be stored in the power grid (N). Only 20% of this latter value can be withdrawn in the form of cash back. It is also worth remembering to substitute the already mentioned 1000 kWh under P in the formula.
This way you will find out what power a photovoltaic installation would have to have to be considered oversized.
Which photovoltaic installation is the most profitable?
After the introduction of new regulations, the situation looks completely different. Surpluses are stored online on a transaction basis. Prosumers resell them at wholesale prices and, if necessary, buy electricity at retail prices. While owners of installations that do not fully cover their needs are exposed to losses, self-sufficient farms can even make money on surpluses. As we mentioned above, up to 20% of the value of energy fed into the network monthly is paid by the operator in the form of a cash refund.
To sum up, it should be said that the larger the photovoltaic installation, the more profitable it is. Selling surpluses (without having to buy them back) can significantly shorten the return on investment period and even generate additional income. The high power of solar panels also means that the farm is adequately prepared for future changes, such as a heat pump or an electric car. When purchases of this type occur, the PV installation will be ready to cover additional demand, without the need for expensive expansion.
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Installation of a PV installation with the Onninen wholesaler
Now that you know how to calculate the power of a photovoltaic installation, check out the wide range of our online wholesaler! Here you will find, among others, modules from well-known and respected brands on the market, such as JA Solar , LG , LONGi Solar and Trinasolar .
Note that it is worth advising future prosumers to invest in the largest possible PV systems. As long as they are limited by the roof area, they are not at risk of being oversized. Such a scenario is only possible if the panels are mounted on the ground. The high power of the photovoltaic installation guarantees measurable savings, additional profits, preparation for future investments, and even - thanks to modules evenly covering the entire roof - an attractive appearance of the building.