Rooftop photovoltaics cannot guarantee energy self-sufficiency for households, German experts have warned (photo: CC0 Public Domain)
Demand for rooftop photovoltaic systems continues to grow, hot on the heels of that of batteries for home use. Recently, the German consumer association Verbraucherzentrale NRW reached out to buyers in an attempt to clarify some details in order to reduce false expectations about photovoltaic installations that could disappoint consumers.
“It’s important to be clear about your personal goals for using PV and then gather more information. In this way, disappointments can be avoided and solar energy can be used really effectively,” said Zoren Demand, energy transition analyst at the consumer association.
The first misconception is people’s belief that they can become energy self-sufficient with PV and storage systems. This is not true, as PV systems and home storage solutions can only cover a certain proportion of annual household electricity consumption.
The degree of self-sufficiency that can be achieved is between 25% and 90%, depending on the level of energy consumption and whether a storage solution is installed. Especially during the winter months, the amount of solar energy that can be generated is far from sufficient to meet the needs of the home’s occupants. Therefore, it becomes necessary to purchase electricity from the grid.
Full energy self-sufficiency can only be achieved with additional seasonal storage such as hydrogen. “However, this is technically complex and hardly makes economic sense for a residential unit,” Demand said.
Solar + batteries
Another misconception is related to the belief that a photovoltaic system is only worthwhile in combination with a battery. Some homeowners seem to believe that feeding solar energy to the grid is not a financially attractive option.
“The PV system pays off financially, even without storage,” commented Demand. “If installing a battery in addition to the PV system is feasible, this decision depends on a number of factors – mainly the user profile of the home and the cost of electricity.”
The Verbraucherzentrale NRW also refutes the idea that south-facing roofs are always better for installing photovoltaic systems than east-west facing roofs. It’s not just about generating as much solar power as possible, it’s about generating electricity when it’s needed.
The annual yield of a photovoltaic system on an east-west roof is about 80% compared to a south-facing roof. However, the yield from solar systems on east-west oriented roofs can be spread over the course of the day, as PV systems enjoy a significant amount of sun in the morning and evening.
Many people who do not have roofs suitable for photovoltaic installations are considering investments in “plug-in” solar devices. They can be attached to balconies or placed in gardens. However, consumers should not expect that they can power household appliances such as coffee machines – this is a false expectation and people may be disappointed.
“These panels are particularly suitable for covering the base load in the household,” explained Demand. “Electricity is used directly – for example for a phone, internet router or clock radio.”
Appliances that require a lot of power for a short time – such as a coffee machine – could not be powered by “plug-in” modules, in such cases the household should resort to electricity from the grid.
Tags: common misconceptions solar panels