From a cost perspective it does not really matter whether wind and photovoltaic systems are probably better erected where it is particularly inexpensive to generate electricity, or instead where the electricity is actually consumed. The overall costs for the change in energy policy in Germany can be reduced in particular through less development of offshore wind power.

On the other hand a decentralized power supply with photovoltaic plants and connected battery storage systems will presumably not be competitive within the next 20 years.

If the best locations are used particularly for the change in energy policy – solar systems in southern Germany and wind-powered installations in the coastal regions – then fewer plants would have to be built altogether; however, an occasional throttling of such plants when there is abundant wind and sun also entails additional costs.

On the other hand, if the plants are built closer to the centers of consumption, then more plants are needed in order to produce the same quantity of electricity, but this at the same time relieves the electricity system as the individual plants would have to be throttled less often because they feed into the mains in closer proximity to the consumers and produce electricity at different periods.

These are the findings of a study by the joint initiative Agora Energiewende, which was presented in Berlin on the optimum costs of development of renewable energies in Germany. "From a cost perspective regional distribution of the plants is virtually insignificant. Thus policymakers have a lot of latitude when it comes to the development of photovoltaic technology and onshore wind power," commented Rainer Baake, director of Agora Energiewende, an institute sponsored by the Mercator Foundation and the European Climate Foundation.

Costs can be saved with the development of renewable energies in Germany particularly through less development of expensive offshore wind power and a greater focus on the more inexpensive wind power installations ashore. According to the study – which was compiled by Consentec GmbH with the support of Fraunhofer Institute for Wind Energy and Energy System Technology (IWES) – the potential annual savings amount to more than 2 billion Euro.

The study was based on the lead scenario of the German Federal Network Agency for the Network Development Plan 2013 and development of renewable energies in Germany by 2023 and 2033 respectively. The experts compared this with their own cost scenarios for production in close proximity to consumption or intensified production at the best locations.

The study also takes account of the electricity supply in Germany, which to a large degree is based on photovoltaic installations and their connected battery systems. A development of 150 GW in photovoltaic output with 40 GW in battery systems by the year 2033. In terms of costs, however, this variant is not yet competitive.

"The prices for decentralized photovoltaic battery storage systems would have to drop by 80% in the years to come in order for such a scenario to lead to comparable overall costs as in the case of the other scenarios. This is not impossible, but it does not appear probable from today’s perspective," noted Baake. The costs of a typical system for a private residential building, a four kW photovoltaic system plus a battery storage system with a capacity of six kWh, would have to drop accordingly from the more than 11,000 Euro at present to approximately 2,000 Euro.