In the long run, your own solar power costs only a third of the electricity from the grid

Enpal offers a rental model for solar systems. The company is responsible for installation, maintenance, repairs and insurance, the customer pays rent and uses their own electricity. The advantage: the customer does not have to invest any money. But initially he hardly earns anything, after 20 years he takes over the system for one euro, then he uses his own electricity without having invested. We spoke to Benjamin Merle, Chief Product Officer at Enpal, about the possibilities of solar technology today - not just for a rental model.

Mr. Merle, at Enpal you don't manufacture your own components, but you supply your customers with solar systems. What are the differences in quality on the market? Which quality features are important?

With panels, what matters is the energy density, which can be specified in watts per square meter or watts per panel. Longevity is also crucial - 25 to 30 years are realistic. This long service life should be secured by the manufacturer with an output guarantee of 20 to 25 years in order to protect the panels from degradation.

So a strong drop in performance of the panels.

Yes, the longer the output guarantee, the better. It is also important that there are now affordable PV optimizers on the market that ensure that electricity is still produced in the event of partial shading. With the inverters, it is important that the dimensioning fits the system and orientation exactly, and thus gets the maximum out of it, even with diffuse light. The inverter should come with an unrestricted manufacturer's guarantee of 10 years. With our rental model, we even guarantee our customers 20 years, during which we bear the costs for the replacement. In principle, we only work with Tier 1 manufacturers - i.e. the direct manufacturers of the systems - to ensure all this. Ultimately, sustainability is important. This is essentially about the possibility of integrating batteries, charging stations or other systems and making them usable together.

One should choose an open system that can be expanded with modules. Tier 1 is the top level, i.e. directly from the manufacturer. As a private customer, I cannot buy there. Which countries do the individual building blocks come from?

For the solar modules, we work together with Longi in China, the largest PV manufacturer in the world. When it came to inverters, we used to have devices from ABB. In the meantime, however, we have switched to Huawei because we have set up our own purchasing department in China. The power storage also comes from Huawei. These are high-quality products at an affordable price, and therefore the best for our customers.

I keep seeing advertisements for photovoltaic systems on Facebook and on the Internet, mostly in shrill tones touting alleged miracles. As a consumer, you're at a loss because you don't know what's behind it. How can you make yourself smart?

There are many supposedly expert blogs and guides on the Internet, which unfortunately can raise even more questions with outdated data and information. Therefore, it is best to find out directly from the provider. Most of their websites already have some information. Many companies, like us at Enpal, offer non-binding consultations and planning, where you can get all your questions answered in a personal phone call.

We have experienced a sharp drop in prices for photovoltaics. What dimensions are we talking about here?

According to Fraunhofer ISE, the costs for PV systems in Germany have fallen by around 75 percent since 2006. So today we have a quarter of the prices of 2006. That's why today's own solar system is the energy to participate - clean, cheap energy from everyone, for everyone!

So the systems are much cheaper today. Is it now wiser to save money and buy a smaller and cheaper system or is it better to invest the drop in price in more capacity?

It often makes more sense to invest in more capacity. The same panels that used to generate 100 watts now generate 400 watts. You also have to think about the assembly costs. It is usually not economical to install only a quarter of the panels because they are more efficient today: once the craftsman is on site, it is usually worth building the entire roof. And anyone who looks to the future knows that in a few years you will probably have an electric car and a heat pump. So he would do well to generate a lot of clean electricity himself on his own roof.

Due to the regulations, it is now more profitable to use the electricity you generate yourself instead of feeding it into the grid. This requires battery storage, but they are also becoming cheaper.

Especially with an e-car, storage can help bring self-sufficiency from the normal 30 to 40 percent to the 60 to 80 percent range. In the favorable case of 80 percent, you then consume almost exclusively your own electricity. This results in customers being independent and green while saving on electricity costs. Depending on the system, we recommend storage between 5 and 10 kWh.

A 10 kWh storage battery can deliver 1000 watts continuously for ten hours. Something like that costs about 6000 euros today. The electricity is green and eco and sustainable. But the question remains, how much does this electricity really cost? You can only give an approximate answer to that. But if you take a rough guess: how much does a kilowatt hour from your own system cost with storage?

Depending on the set-up, the electricity from your own photovoltaic system costs around 10-15 cents per kilowatt hour - compared to today's electricity price of 30 cents.

So we're talking about half or a third of the current electricity price. And it will continue to rise over the next 20 years. In 2010 it was around 23 cents, today it is over 30 cents. If you charge an e-car at a public charging station, up to 80 cents per kilowatt hour are due.

That's right, the calculated price for your installation will not increase, but the price for the mains electricity will increase. We're talking about a lifespan of up to 30 years, maybe even 35 years. So the gap keeps widening. One does not exaggerate when one says: In the long run, the electricity from your own photovoltaics costs a third of the mains electricity. For exact values, you must of course have a specific project calculated. A PV system is almost always worthwhile if the customer can use the electricity at home. In addition to the usual consumers in the household, there are also e-cars and heat pumps. And as you said, the price difference between your own solar power and that from a public charging station is enormous. If you buy an e-car, your own photovoltaic system is a must.