The 21energy PV Calculator: How to Use the Tool Effectively for Your Photovoltaic Planning

August 11, 2025

Choosing a photovoltaic system (PV system) is a major step toward sustainable energy supply and cost savings. To help you plan effectively, 21energy offers the PV Calculator – a practical online tool that quickly and easily shows how much solar power you can generate with a PV system on your roof.
But how exactly does the calculator work? And how can you correctly interpret the results? In this article, we’ll walk you through how to use the 21energy PV Calculator effectively, step by step.

More profit from your PV system

See how much extra profit your solar surplus can generate through Bitcoin mining instead of feeding it into the grid.

Calculate earnings

Up to 5× greater returns than standard feed-in tariffs

Seamless plug-and-play setup

Daily payout & full transparency

What is the 21energy PV Calculator?

The PV Calculator is an interactive tool that provides a realistic estimate of your potential photovoltaic system's performance using just a few details about your location, roof, and energy consumption. It calculates:

The potential installable capacity (kWp) on your roof
The expected annual electricity production (kWh)
Your self-consumption rate and potential savings
The CO₂ emissions you can save by using solar power

This gives you a clear initial overview of whether a PV system is worthwhile for you – and to what extent.

Step-by-Step: How to Use the PV C

alculator Correctly

1. Enter your location
Enter your address or place of residence. The calculator will use this information to determine solar radiation and climate at your location – both critical for estimating solar power generation.

2. Specify your roof area and orientation
Describe the available roof area for installation. Orientation (south, east, west) and roof pitch significantly influence the system’s efficiency.

3. Enter your annual electricity consumption
Provide your current electricity usage – this is important to determine your self-consumption rate and to see how much of your generated electricity you can use directly.

4. Optional inputs
Sometimes you can enter additional details, such as whether you plan to use a battery storage system or the level of your feed-in tariff.

5. Start calculation
Click “Calculate” and wait for the results.

How Do I Find Out My Annual Electricity Consumption?

To get an accurate calculation from the PV Calculator, you should know your annual electricity usage in kilowatt-hours (kWh) as precisely as possible. Here’s how:

Check your electricity bill
Your annual bill from your energy provider usually includes a summary of total consumption over the last year – often labeled as "total consumption" or "annual usage in kWh."
Compare multiple bills
If you have access to several bills (e.g., from the past 2–3 years), you can calculate an average – especially helpful if your usage has changed recently due to new appliances or an electric car.
Read the meter manually
If no bill is available, you can note your current meter reading and compare it to last year’s (e.g., from photos, emails, or apps).
Use online tools or customer portals
Many electricity providers offer a customer portal or app where you can view your electricity consumption by day, week, or year.
Use estimates if uncertainIf you don't know your consumption yet (e.g., for a new home), you can use rough estimates:
- 1-person household: approx. 1,500–2,000 kWh/year
- 2-person household: approx. 2,000–3,000 kWh/year
- 3–4 persons: approx. 3,000–4,500 kWh/year
- With electric car or heat pump: more accordingly

The more accurate your input, the more realistic the PV Calculator’s results – and the better you can plan your photovoltaic system.

How Do I Interpret the Results?

Installable Capacity (kWp)
This tells you the maximum peak power your PV system can generate. The higher the capacity, the more electricity you can produce.

Annual Electricity Production (kWh)
An estimate of how much electricity your system is likely to generate per year. This depends on your location, roof area, and orientation.

Self-Consumption Rate and Savings
How much of your electricity usage can be covered by your own solar power? The higher this share, the greater your savings on electricity bills.

CO₂ Savings
The calculator also shows how much CO₂ emissions you can avoid by using solar power – a valuable contribution to environmental protection.

What Are the Benefits of the PV Calculator?

Initial Guidance: Get a quick and simple estimate of whether a PV system is worth it for your home.
Planning Support: Understand the key parameters of a solar installation (size, orientation, etc.).
Estimate Cost Savings: See how much money you could save through self-consumption.
Environmental Impact: Discover how your system can help fight climate change.

Conclusion

The 21energy PV Calculator is a valuable tool that lets you easily calculate your potential solar power production. It provides essential first insights for your personal energy transition and shows you the opportunities a photovoltaic system can offer. Use the calculator as a starting point for your PV planning – and then get personalized advice to help you implement your solar project effectively!