Say NO to oversizing PV systems due to winter production declines

It seems like an easy way to save on energy and, for some, even make a profit: install the largest possible photovoltaic system that will produce as much as possible for your needs in winter and generate so much surplus in summer that you can sell it to the grid at a profit. But in reality, it doesn't work that way. Even a significantly oversized PV system will certainly not be able to cover your winter consumption completely. In summer, on the other hand, you will have to deal with a large amount of surplus energy at a time when no one really wants it.

Optimal size of a photovoltaic system
When designing a photovoltaic system, it is therefore best to consider two aspects: the space available and your electricity consumption.

• Space: When installing a PV system on the roof, you must comply with safety regulations, such as the spacing or distance of the panels from skylights or lightning rods and the maximum roof load. In other words, it is not possible to "cram" panels onto the entire roof.
• Your electricity consumption: The aim is to design a photovoltaic system with a capacity that allows you to consume as much of the energy produced as possible and feed only a minimum into the grid. Some overflow is to be expected in summer, but it should not be too high. In many cases, high overflows will not even be permitted by the distribution system operator.

Why PV systems do not cover consumption in winter
Although photovoltaics produce energy all year round, there is a significant difference between summer and winter production. This is mainly due to short days and winter weather – overcast skies and possible snowfall limit the impact of direct sunlight on the panels. Snow on the panels or frost also reduce production.

On the other hand, increased electricity consumption counteracts reduced winter production. In winter, you spend more time at home, using lights, heating, heating water, and so on. Moreover, this is mainly during the hours when it is already dark outside and the panels are not producing anything. Electricity consumption is therefore high, photovoltaic production is low, and you have to draw most of your electricity from the grid.

The lowest production and, conversely, the highest consumption are in January and December. The difference between production and consumption is so great in these months that it is not realistic to oversize the photovoltaic system to cover this difference.

What to do with summer surpluses
Distributors have to deal with surpluses so as not to jeopardize the stability of the distribution system. If most households had oversized photovoltaic systems and their surpluses were huge, there would be a significant surplus of electricity in the grid. In extreme cases, this could lead to a blackout. This is one of the reasons why distributors do not want high overflows from domestic photovoltaic systems and often prohibit them by setting a reserved capacity – a notional maximum that you can send to the grid.

What to do with unused electricity
There are four ways to deal with unused electricity that overflows from your system.

Store it in a physical battery you have at home
You can use the electricity later, for example at night when the panels are not producing. You are sure to find what you need in our wide range

Sell the excess
In this case, it is necessary to conclude a contract with your supplier for the purchase of electricity. The contract specifies the terms of purchase and the amount you will receive for the surpluses. However, the price for surpluses is usually not attractive enough to make it worthwhile to oversize your photovoltaic system.

Use a virtual battery
This is a service that evaluates the overflow sent to the grid. A virtual battery works like an imaginary energy loan: the energy produced by your panels is taken over by your supplier – they borrow it. They return it to you at a time of year when your photovoltaic system is not producing as much, for example in winter – you do not pay for the electricity you have taken. However, this does not apply to the regulated component, which accounts for about 50% of the energy price.

Electricity sharing
In practice, this means that the excess electricity generated by your photovoltaic system is also used by your neighbor. However, this is still considered overflow, so you are limited by the value of your reserved capacity.