What is photovoltaic system funding calculation and how is it carried out correctly?

A photovoltaic system funding calculation in Germany is less about one government grant and more about several building blocks that you can each convert into euros. Most of the money comes from the EEG feed-in tariff and from the electricity you no longer have to buy from the grid. On top of that come 0% VAT, the income tax exemption, the KfW 270 loan and, in some regions, a grant such as proKlima. Here we show you the formulas, the current rates and a complete worked example for 10 kWp in which every assumption is stated openly.

Photovoltaic system funding calculation: key facts at a glance

Why is photovoltaic system funding calculation so important for your investment?

Many quotes include «funding» without saying what it consists of. A clean funding calculation for your photovoltaic system shows you which part is fixed (the EEG rate for 20 years), which part depends on your behaviour (self-consumption) and which part comes only once (tax advantage, grant). Only then can you compare quotes and judge realistically when the system pays for itself.

What is meant by photovoltaic system funding calculation?

It means working out how much money the state and regional benefits bring you per year and over the lifetime. There is no general federal grant for private PV systems or battery storage in Germany. A photovoltaic system funding calculation therefore combines income (feed-in tariff), savings (less grid electricity), tax advantages and, where available, a regional grant. You will find an overview of all programmes on our page about solar subsidies in Germany.

Which factors influence the funding calculation for a photovoltaic system?

• System size in kWp: it determines the tariff band (up to 10, 40 and 100 kW) and the amount of any per-kWp grant.
• Yield: for the Hannover region we calculate cautiously with about 893 kWh per kWp per year. On an optimal south roof PVGIS gives about 1,000 kWh/kWp; an east-west roof yields about 80% of that (more on orientation).
• Self-consumption share: about 25–35% without storage, 55–70% with storage.
• Electricity price: the more expensive your grid power, the more each self-used kilowatt-hour is worth.
• Commissioning date: the EEG rate valid on that day stays fixed for 20 years.
• Feed-in model: partial or full feed-in.

More efficient modules do not get a higher tariff, by the way. Efficiency only matters indirectly through the yield.

What types of funding are included in the calculation?

1. EEG feed-in tariff

For every kilowatt-hour you feed into the grid, the grid operator pays you the rate that applied at commissioning, for 20 years. Formula: kWh fed in × tariff = income per year. Details on rates and registration are in our article on the EEG for photovoltaics.

2. Avoided grid purchase

Strictly speaking not funding, but the biggest item: every kilowatt-hour you use yourself does not have to be bought at the household price. Formula: self-consumed kWh × electricity price = savings per year. Because your electricity price is well above the feed-in tariff, using your own power pays more than feeding it in.

3. 0% VAT

Since 1 January 2023 the zero rate applies to the supply and installation of PV systems and storage on or near residential buildings (§ 12 (3) UStG). Up to 30 kWp the conditions are deemed to be met automatically. In effect you save 19% on the net price, once, at purchase. More on photovoltaic system VAT.

4. Income tax exemption

Income from systems up to 30 kWp per residential or commercial unit (max. 100 kWp per person) is tax-free under § 3 No. 72 EStG. The feed-in income therefore goes into your calculation without deductions. Details: tax-free photovoltaic system.

5. KfW 270 loan

KfW 270 «Erneuerbare Energien – Standard» is a loan, not a grant. It spreads the cost over the term but costs interest. In the calculation it is therefore a way of financing, not income. You apply through your bank before placing the order. More on KfW funding for photovoltaic systems.

6. Regional grants such as proKlima

In Hannover, Hemmingen, Laatzen, Langenhagen, Ronnenberg and Seelze, proKlima’s DachVollToll programme pays €100 per kWp, up to €2,000. Conditions include an existing residential building, at least 2 kWp and fully covered roof surfaces. The grant is only available while funds last and only if you apply before placing the order. All details on regional programmes: solar funding in Hannover.

Calculating the feed-in tariff: rates and formula

Feed-in rates for photovoltaic system funding calculation

For rooftop systems commissioned from 1 August 2026 the Federal Network Agency (Bundesnetzagentur) lists these rates:

The rates are adjusted every six months. What counts is the rate on the day of commissioning. The planned EEG amendment is so far only a government draft (Bundestag document 21/7867). Systems commissioned by 31 December 2026 keep the fixed tariff for 20 years (more under EEG amendment).

Photovoltaic system above 10 kWp: proportional funding calculation

Larger systems do not get the lower rate for everything. Under § 23c EEG the payment is split proportionally by capacity. For 15 kWp with partial feed-in: (10 × 7.70 + 5 × 6.66) ÷ 15 = about 7.35 ct/kWh on average. For 30 kWp: (10 × 7.70 + 20 × 6.66) ÷ 30 = about 7.01 ct/kWh.

Partial or full feed-in?

With partial feed-in you use power yourself and only export the surplus. With full feed-in everything goes to the grid, at a higher rate. You must notify the grid operator of full feed-in in text form before commissioning, and later before 1 December for the following year (§ 48 (2a) EEG). For a normal family home with its own consumption, partial feed-in almost always works out better, as the example below shows.

New systems without a smart metering system may also feed in at most 60% of their capacity, and the tariff may not be paid during periods of negative exchange prices. What this means for you is explained in our article on the solar peak law. These effects are not deducted in the example.

Worked example: photovoltaic system funding calculation for 10 kWp

Assumptions of the funding calculation for the photovoltaic system

Result per year: without storage, with storage, full feed-in

The feed-in tariff itself is the smaller part. Without storage it adds up to about €9,620 over 20 years at constant feed-in, tax-free. The bigger part is the savings. Each extra cent on the electricity price adds about €27 per year in the example without storage, and about €54 with storage. Full feed-in does not pay off here, because 12.22 ct is well below the value of a self-used kilowatt-hour. Whether battery storage pays off for you depends mainly on the extra cost and your consumption profile.

What 0% VAT and proKlima add

With 19% VAT the system without storage would cost about €2,760–3,330 more, with storage about €4,220–5,070 more. This advantage is already included in the prices above. If your home is in the proKlima area and funds are still available, you get an extra €1,000 for 10 kWp (€100/kWp). That lowers the investment without storage to €13,500–16,500.

How is the payback period calculated?

Simplified: investment ÷ benefit per year = years to payback. With the assumptions above:

• without storage: €14,500–17,500 ÷ €1,339 → about 11 to 13 years
• without storage, with proKlima: €13,500–16,500 ÷ €1,339 → about 10 to 12 years
• with storage: €22,200–26,700 ÷ €1,990 → about 11 to 13 years
• full feed-in: €14,500–17,500 ÷ €1,091 → about 13 to 16 years

For comparison, our reference project in Rethen (10.2 kWp with BYD storage, €21,400): there the payback in the worked example is about 9.7 years. The reason is the higher yield forecast for that specific roof (approx. 9,800 kWh per year) at €0.32/kWh and an 8.2 ct feed-in tariff at its commissioning date. The detailed cost and return calculation is on 10 kWp photovoltaic system cost. Whether PV pays off for you overall, with price scenarios and lifetime, is answered in is photovoltaics worth it.

What mistakes should be avoided in the calculation?

• Counting grants that do not exist: there is no federal grant for private PV or storage. The KfW loan is not free money.
• Assuming too much self-consumption: without storage 25–35% is realistic, not 50% or more.
• Using the wrong EEG rate: the rate on the commissioning day counts, and above 10 kWp it is calculated proportionally.
• Applying too late: proKlima and KfW 270 must be applied for before you place the order, otherwise you lose the entitlement.
• Forgetting registration: the system must be entered in the Marktstammdatenregister within one month of commissioning, otherwise the tariff can be reduced.
• Hiding assumptions: a photovoltaic system funding calculation without a stated electricity price and yield cannot be checked.

For a first estimate, simply replace the values in the assumptions table above with your own yield, consumption and electricity price.

How we calculate your quote

Our quote shows the funding calculation for your photovoltaic system with every assumption: yield forecast for your roof, assumed electricity price, self-consumption with and without storage, and the EEG rate for the planned commissioning date. We check whether proKlima or another regional programme applies to you and tell you what must be applied for before you place the order. You get a written fixed price and pay according to the 30/70 model.

Want to see your own calculation? Request a free, non-binding quote now. You can also call us on 0511 3360603 or message us on WhatsApp at +49 176 2399 8536.

Sources:

1. Bundesnetzagentur: EEG funding and feed-in rates for solar systems (German)
2. § 23c EEG: proportional payment and § 48 EEG: solar systems, full feed-in
3. § 12 (3) UStG: zero VAT rate
4. § 3 No. 72 EStG: tax exemption
5. KfW: Erneuerbare Energien – Standard (270)
6. proKlima: DachVollToll

Note: This article gives a general overview (as of November 2026) and does not replace tax or legal advice.