Solar Calculator: How to Calculate Yield, Costs and Payback

What will a solar system on your roof produce, what will it cost and when will it pay for itself? You don’t need a complicated solar calculator for that. With five simple steps and a few guide values, you can estimate the key figures yourself. Here we show you how, which free online calculators are genuinely reliable, and where every online calculation reaches its limits.

Want an accurate calculation for your roof? Request your free, no-obligation quote now. We’ll prepare a free yield forecast using your real data.

It’s quicker with our solar calculator (in German): enter your household consumption, system size and, if you like, a battery, heat pump and EV, and you immediately see how much you save and how much of your electricity you cover yourself. No sign-up, no phone number.

Solar Calculator: Key Facts at a Glance

Calculate Your Solar System Yourself in 5 Steps

Step 1: Determine the System Size

The size depends mainly on your usable roof area. As a rule of thumb, with today’s modules you need about 5 to 6 m² of roof area per kWp. For 10 kWp, that’s roughly 50 to 60 m². With a heat pump or an EV, it usually pays to cover the entire suitable area.

Step 2: Estimate the Annual Yield

Formula: system size (kWp) × specific yield (kWh per kWp) = annual yield

In the Hanover region, we calculate about 893 kWh per kWp per year. A south-facing roof with a 30 to 35 degree pitch tends to be higher, while an east-west roof or shading tends to be lower. Example: 10 kWp × 893 kWh = just under 9,000 kWh a year.

Step 3: Estimate Self-Consumption

Formula: annual yield × self-consumption rate = solar power used on site

Without a battery, a typical household uses about 25–35% of its solar power itself, and about 55–70% with a battery. Importantly, the power you use yourself can never exceed your annual consumption. If the system generates far more than you use, the rate will be at the lower end.

Step 4: Calculate the Annual Benefit

Formula: self-consumed power × electricity price + power fed in × feed-in tariff = benefit per year

Use your own electricity price from your bill. In our examples, we assume 37 ct/kWh. Since 1 August 2026, new systems up to 10 kWp with partial feed-in have earned about 7.70 ct/kWh for power fed into the grid.

Step 5: Calculate the Payback Period

Formula: purchase cost ÷ benefit per year = payback period in years

As a guide to costs, we calculate about €1,450–1,750 per kWp without a battery, so about €14,500–17,500 for 10 kWp. With a BYD HVS 10.2 battery, it’s about €22,200–26,700.

Worked Example: 10 kWp in the Hanover Region

A four-person household uses 4,800 kWh a year. Assumed electricity price 37 ct/kWh, feed-in tariff 7.70 ct/kWh, no electricity price increase:

Why only 45% with a battery? The system generates almost twice as much power as the household uses. You’ll find more explanation of this example under is solar worth it?

Want this calculation with your own figures? Request your free, no-obligation quote now.

Our Solar Calculator

With the PVPro Solar calculator (in German), the steps above are calculated automatically. You start with a few details, annual consumption, PV output, battery, electricity price and feed-in tariff, and can then refine everything: people in the household, roof pitch, roof type and orientation, a heat pump with living area and building condition, and an EV with mileage and charging strategy. The result shows your annual savings and how much of your electricity, heat pump and EV demand you cover with solar power. You don’t need to sign up or give a phone number.

Independent Online Calculators for Cross-Checking

• HTW Berlin independence calculator: an independent calculator from the Berlin University of Applied Sciences (HTW Berlin). It shows how much of your consumption you can cover yourself with a PV system and battery, which makes it useful for comparing battery sizes.
• PVGIS from the European Commission: a free tool from the EU’s Joint Research Centre. It calculates the annual yield for your exact location, pitch and orientation.

Both tools are manufacturer-neutral and need no registration. Be careful with calculators that ask for your phone number before showing a result. They often exist mainly to pass your data on to providers.

What Else Changes the Calculation

• Electricity price trend: we calculate without electricity price increases. If prices rise, the payback period gets shorter, because every self-consumed kilowatt-hour is worth more.
• Module ageing: modules lose some output over the years; about 0.5% a year is a common assumption. The exact values are in the manufacturer’s performance warranty.
• Inverter replacement: an inverter usually lasts 10 to 15 years. Plan for one replacement over the system’s lifetime; more under solar inverters.
• Funding: in parts of the Hanover region, proKlima funding comes on top; see solar funding in Hanover.

Where Every Solar Calculator Reaches Its Limits

Online calculations work with averages. They can’t capture these points, or only roughly:

• Shading: trees, dormers or neighbouring houses often reduce the yield more than expected.
• Roof condition and structure: if the roof needs renovating first, the whole calculation changes.
• Meter cabinet: a necessary modification costs extra and doesn’t appear in any online calculator.
• Your consumption profile: whether you’re at home during the day or use a lot of power in the evening changes self-consumption significantly.
• Heat pump and EV: they shift demand considerably, and differently in winter than in summer.
• Changes in the law: according to the government’s draft EEG amendment 2027, the fixed feed-in tariff is set to fall significantly for new small systems. Systems commissioned by 31 December 2026 keep the fixed rate for 20 years.

An online calculation is therefore a good guide, but not a quote. For a reliable figure, someone needs to look at your roof and meter cabinet.

Your Personal Calculation from PVPro Solar

We offer a free initial consultation with roof analysis and a yield forecast for your roof. We take into account your actual consumption, shading and, if you like, a battery, wallbox or heat pump. You then receive a fixed-price quote with modules from AIKO, JA Solar or Longi, a Fronius inverter and an optional BYD battery. You pay using the 30/70 model. You can see how the quote is structured on our free photovoltaic quote page.

Request your free, no-obligation quote now, or call us on +49 511 3360603 or message us on WhatsApp at +49 176 2399 8536.

Frequently Asked Questions About Solar Calculators

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