Sonnen adds electric cars and rooftop PV to its monthly payment plan


From pv magazine Germany.

German storage system supplier Sonnen is now offering ‘sonnenDrive’ electric cars and ‘sonnenNow’ PV systems with storage under its subscription model to members of its solar community.

Ownership of a Sonnen residential energy storage system brings membership of the ‘sonnenCommunity' and now offers the chance to have a household PV system installed and to own an electric vehicle (EV) in return for staggered monthly payments.

With tariffs designed to be cheaper than comparable purchasing methods, Sonnen founder and CEO Christoph Ostermann told delegates at Berlin’s E-Werk conference venue, the payment system is designed to remove all reasonable objections to trying out the products available. Why not install an affordable PV system, for example, and why not try an EV if you plan to change your car anyway? “If you don’t do it now, you just don’t want to,” said the chief executive on Thursday.


The EV subscription model which will be offered from January 1 differs from leasing contracts in several respects. For example, Sonnen community members can opt to join sonnenDrive for as little as six months, whereas leases typically have a minimum term of at least two years. The Sonnen offering requires no down payment and insurance premium costs are included with the simplest EV models available for less than €300 per month.

“There is no cost disadvantage [compared] to the petrol engine,” said Ostermann.

Initially the Renault Zoe and a larger model will be available but Sonnen intends to expand the choice of car available and may add a Tesla next year.

The chief executive estimates 30% of Sonnen home storage customers who take up the option of subscribing to a PV array will also take up the EV offer.

The subscription model for adding a residential solar system lasts 20 years, although it can be paid off early at any point. SonnenNow differs from other solar leasing deals in that it guarantees to provide all the energy required by the household, as the monthly payments are geared to electricity consumption as well as system size.

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The business case

“You have monthly expenses roughly in the amount of the previous electricity bill, sometimes a little over or under,” said Ostermann, whose company will also shoulder the risk of carrying out repairs during the term of the arrangement.

Sonnen gives the example of a household which consumes 3.5 MWh of electricity and pays €90 per month under SonnenNow, a payment which includes the cost of supplying all its power. A 20-year subscription would add up to €21,600, not much more than the €21,000 cost of a grid connection offering electricity at €0.30/kWh. Larger PV systems can reduce the monthly payment further.

Sonnen’s business case is driven by the fact it will bank any feed-in tariff (FIT) allocated for excess power generated by the system and fed back into the grid. Although the German FIT is falling, Ostermann is confident continuing falls in the cost of PV systems and batteries will continue to make the model stack up for his business.

Simplifying solar

There is still an incentive to pay up front for a PV system for households with sufficient funds, according to the Sonnen CEO, as the 20-year payment includes an element of interest, but he said the subscription payment method opens up solar to far more households.

The German company says it has delivered 50,000 battery storage units worldwide, many of them networked and the company’s founder has called on politicians to follow his lead by making access to solar as simple as possible for as many people as possible. Ostermann called for the abolition of double taxation on energy storage facilities, freeing them up for grid balancing services, such as those Sonnen is testing with wind power generation for Dutch electricity transmission system operator Tennet.

He also suggested further simplifying the form required to connect solar systems adding: “If you no longer have to fill out four-page forms, there could be a boost.”

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