Misconceptions about Residential Solar

The demand for home rooftop photovoltaic (or solar) systems and residential batteries is increasing. In order to meet the expectations of homeowners, Verbraucherzentrale NRW, the German Consumers' Association, is trying to clarify misunderstandings about photovoltaic installations that could lead to disappointment for professional consumers.

Sören Demandt, digital transformation analyst for energy at Verbraucherzentrale NRW, said: "It is very important to make people aware of their individual goals for using photovoltaics and then to find out more information about it. In this way, disappointments can be avoided and solar energy can be used effectively."

The first misunderstanding is the promise to people that they can become self-sufficient through photovoltaic power generation and storage systems. The truth is, however, that a photovoltaic system and a home storage solution can only meet a certain proportion of the household's electricity supply per year.

The extent to which households can become self-sufficient ranges from 25% to 90%, depending on the electricity consumption level and whether a storage system has been installed. Demandt said that the solar power generated is far from enough, especially in the winter months, so electricity must be purchased from the grid. Complete self-sufficiency can only be achieved through additional seasonal storage, such as hydrogen.

"But this is technically very complex and hardly economically viable for residential units," Demandt said.

Another misunderstanding is that photovoltaic systems are only valuable when combined with batteries. Some homeowners seem to think that connecting solar energy to the grid is not an attractive option from an economic point of view.

"Even without storage devices, photovoltaic systems still have economic value," Demandt said. "The feasibility of installing a battery storage system for a photovoltaic system depends on several factors – primarily the household's consumption pattern and electricity costs."

Therefore, homeowner should check their electricity consumption level without installing a storage system. They can compare the higher electricity consumption level achieved after installing a battery storage system with the actual electricity bill generated.

Verbraucherzentrale NRW does not agree with the view that south-facing roofs are always better for installing photovoltaic systems than east-west facing roofs. Photovoltaic power generation does not only pursue the maximum possible electricity output but also needs to meet the continuous electricity demand. Compared with south-facing roofs, photovoltaic systems installed on east-west facing roofs only generate around 80% of electricity in a year. However, the solar energy system installed on east-west facing roofs can spread the power generation throughout the day because it still receives a lot of sunlight in the morning and evening.

Many homeowners do not have roofs to install photovoltaic equipment, so they usually consider investing in plug-in solar equipment. Such equipment can be installed on balconies or in gardens. However, if the occupants want them to power household appliances such as coffee machines, they may be disappointed.

"These panels are particularly suitable for covering the basic load of households," Demandt explained. "The power is used directly, for example for telephones, network routers or alarm clock radios."

More electricity demand will be provided by the grid. For example, a coffee machine requires about 2000 W of heat to boil the water. According to Verbraucherzentrale NRW, this goal cannot be achieved solely by balcony photovoltaic components.