Solar calculator for commercial roofs, solar parks and Agri-PV

Depending on the federal state about 1,020 to 1,170 kWh per year with south orientation, optimal tilt and no shading, derived from the global radiation data of the German Weather Service (factor 0.985 according to Fraunhofer ISE). East-west plants deliver about 18 % less per kWp, single-axis trackers about 18 % more. Curtailment comes on top, see the next question.

Because solar parks no longer sell every kilowatt hour. Yield reports assume about 1,080 full-load hours, while the German transmission system operators expect only 864 for new ground-mounted plants in 2026 (Fraunhofer ISE). Since 25 Feb 2025 the subsidy also lapses in every quarter hour with a negative power price (§ 51 EEG). The calculator therefore deducts 10 % for solar parks, 8 % for Agri-PV and 3 % of the feed-in for commercial roofs by default. The value is an estimate and can be changed under “Adjust assumptions”.

As a reference up to 1.0 MWp about €750 per kWp, up to 10.0 MWp about €620 per kWp, up to 300.0 MWp about €580 per kWp, net and without grid connection outside the park. A 10 MWp plant therefore costs about €6.2m. The official ZSW assumption for commissioning in 2026 is 540 to 560 €/kWp, but it is based on the module price low of October 2024; Fraunhofer ISE reports clearly higher system costs for 2025.

Fixed south-facing about 1.0 ha per MWp, east-west about 0.8 ha, with single-axis trackers about 1.2 ha. Agri-PV with trackers and driving lanes needs about 1.8 ha per MWp because farming continues between the rows.

Usually yes, if power is needed during the day. In the example of 300 kWp in Bavaria with daytime operation the business uses 70 % of the solar power itself, the levelised cost of electricity is about 7.1 ct/kWh against 23.5 ct for grid power, and the plant pays for itself after about 4.3 years.

From 100 kW installed capacity (§ 21 EEG). Instead of a fixed feed-in tariff you then receive the market premium: the reference value for rooftop plants up to 1 MW is 5.84 ct/kWh (BNetzA, from 1 Aug 2026), of which about 0.3 ct goes to the direct marketer. Up to 100 kW the feed-in tariff applies proportionally by tier: 7.70 ct up to 10 kW, 6.66 ct up to 40 kW, 5.44 ct up to 100 kW.

Plants commissioned by 31 Dec 2026 keep today's tariff for 20 years. The draft EEG 2027 (Bundestag paper 21/7867, not yet passed) provides no fixed tariff for new plants afterwards, only a transition payment of 5.2 ct/kWh for 36 months, a tender obligation for ground-mounted plants from 750 kW and a ceiling of 5.9 ct/kWh in tenders. The calculator uses the values in force today.

Agri-PV combines farming and solar power on the same land. Under DIN SPEC 91434 ground-level systems may lose at most 15 % of the area, and the agricultural yield must reach at least 66 % of the reference yield. With trackers and driving lanes about 85 % of the land stays farmable and the tractor drives between the rows. The Agri-PV bonus of 0.5 ct/kWh in tenders only applies to elevated systems with at least 2.10 m clearance.

Leasing brings predictable income without risk: about 2,500 to 4,000 € per hectare and year are common, for Agri-PV rather 2,000 to 3,000 € because the land keeps producing (there are no official statistics). Investing yourself brings the power revenue, but also capital needs and marketing risk. The calculator shows both options side by side for your land.

On a commercial roof it raises self-consumption: in the example it rises from 70 % to 86 % with 200 kWh of storage. In a solar park it shifts midday power into higher-priced evening hours. Peak shaving and balancing energy are not included; with them, storage often pays off considerably better in practice.

The cost per usable kilowatt hour over the entire lifetime: investment plus discounted operating costs, divided by the discounted energy yield. At a 5.0 % discount rate it is also the minimum price at which the plant earns that return. Fraunhofer ISE gives 4.1 to 6.9 ct/kWh for ground-mounted plants in Germany, depending on the site.

It provides reference values for the project idea, not a yield report. Shading, grid connection, ground conditions, your load profile and the actual award change the result. All assumptions are listed with sources on this page and can be changed; for a reliable offer we calculate with your project data.

No. KXS Energy builds commercial roofs, solar parks, Agri-PV and storage, single projects up to 160+ MW. The home roof mode in the calculator is a service; for a home roof we recommend a local installer.