In short
Repowering pays off if the income value after the upgrade, minus the investment, is higher than the value from continued operation. For systems with a running tariff, a tariff-preserving module replacement can make sense; after the tariff ends, self-consumption usually decides.
Three options compared
What happens to the tariff
Since Germany's Solar Package I (16 May 2024), modules on buildings may be replaced without a defect and still keep the original tariff rate. It applies only to the share of electricity corresponding to the old capacity. Additional capacity receives the current tariff. The replacement must be reported (Clearingstelle EEG|KWKG, in German). We check whether the conditions are met in the individual case before valuing.
How we compare
- Income value from continued operation, with a realistic decommissioning year
- Income value after repowering, with new capacity, tariff split and self-consumption
- Investment, removal of old modules, downtime
- Difference between both values minus investment, with sensitivity to electricity price and yield
For the first option, the calculator gives an order of magnitude. We calculate the comparison with repowering in the report.
Costs not shown in the quote
The installer's quote lists modules, inverters and installation. Three items are often missing for the value comparison.
First, downtime: from dismantling onwards no tariff is paid until the new system runs. Second, disposal: old modules have been covered by the German Electrical and Electronic Equipment Act since 24 October 2015. Take-back through manufacturers or their schemes is free, dismantling and transport are not (Solarenergie-Förderverein, German). Third, the roof: if it needs renovating anyway, a second dismantling and reinstallation is avoided. That can tip the balance towards a full repowering.
What applies to the new capacity
The additional capacity receives the tariff applicable at the time of replacement. Systems commissioned from 25 February 2025 receive no tariff at negative exchange prices, and the support period is extended by those periods (Clearingstelle EEG|KWKG, German). Whether this applies to the new share of a repowered system is checked case by case based on its commissioning date.
A battery can shift midday power into the evening and raise self-consumption. Whether it pays off is shown by the variant calculation with and without storage.
Self-consumption instead of feed-in
After the tariff ends, exported power only earns the market value. Every kilowatt hour used on site, by contrast, replaces grid power at 25 to 35 ct. Repowering after the tariff ends therefore almost always pays off through self-consumption, hardly through feed-in. We derive the share from load profiles or meter data, not from rules of thumb.
Registration and permits
New modules and inverters must be registered with the grid operator and updated in the Market Master Data Register. For listed buildings, the new layout may need its own permit even if the old system was approved.
Before or after the tariff ends?
Before the tariff ends, replacing modules on buildings keeps the old rate for the original capacity. After it ends there is nothing left to lose, but only self-consumption counts. Which timing is better depends on the condition of the modules and on how much tariff is still outstanding.
Frequently asked questions
Does repowering a PV system pay off?
If the value after the upgrade minus the investment is higher than with continued operation. Typical triggers are damage, a roof renovation that is due anyway or high self-consumption.
Do I keep the old tariff when replacing modules?
For systems on buildings, since Solar Package I generally yes, for the share of electricity from the original capacity. The replacement must be reported.