Estimate annual yield
PV size and location define the expected generation.
Guide
Understand solar PV: does your PV system really pay off?
Solar only pays off when roof yield, self-consumption, electricity price and investment cost work together. Installed capacity alone does not decide the economics.
Quick answer
When does solar PV pay off?
Set self-consumption. The more solar power is used on site, the less the economics depend on feed-in tariffs, weather and ideal yield assumptions.
Example
Example: Self-consumption drives PV economics
Start by clarifying whether the PV system pays off economically and energetically. Then the comparison clarifies the effect of system size, yield, self-consumption, electricity price, cost and export and the boundary set by roof orientation, shading, degradation, price trends and financing.
Decision focuswhether the PV system pays off economically and energetically
Main leversystem size, yield, self-consumption, electricity price, cost and export
Separate checkroof orientation, shading, degradation, price trends and financing
Next stepjudge self-consumption and payback together, not yearly yield alone
How to read the resultDecision focus: whether the PV system pays off economically and energetically. Separate check: roof orientation, shading, degradation, price trends and financing.
Read the result together with system size, yield, self-consumption, electricity price, cost and export. Roof orientation, shading, degradation, price trends and financing limit how directly you can act on it.
Decision view
Self-consumption drives PV economics
The overview separates result, lever and boundary: whether the PV system pays off economically and energetically; system size, yield, self-consumption, electricity price, cost and export; roof orientation, shading, degradation, price trends and financing. The overview shows the statement first, then the influence and then the limit.
What the visual shows
The values explain the most important parts of the visual.
Resultwhether the PV system pays off economically and energetically
Main leversystem size, yield, self-consumption, electricity price, cost and export
Separate checkroof orientation, shading, degradation, price trends and financing
The practical benefit becomes clear only when system size, yield, self-consumption, electricity price, cost and export are realistic and roof orientation, shading, degradation, price trends and financing are checked separately.
The load profile, weather, shading and inverter losses can change the economics; use the calculation as an annual model, not as a yield report. Roof orientation, shading, degradation, price trends and financing can change the real-world result and should be reviewed separately before binding decisions.
How it is calculated · Mathematical background
How it is calculated
The formula explains the number. The practical statement also depends on roof orientation, shading, degradation, price trends and financing.
Separate self-consumption
Directly used solar power replaces expensive grid electricity.
Value feed-in
Power not used at home is valued at the feed-in tariff.
Build annual value
Savings and feed-in revenue are combined.
Compare investment
Purchase and running costs are compared with the annual value.
Review payback
The payback period makes clear whether the scenario is robust.
The result stays robust when system size, yield, self-consumption, electricity price, cost and export are realistic and roof orientation, shading, degradation, price trends and financing are not overlooked.
Detailed calculation explanation
PV economics come from the value of self-used electricity plus feed-in revenue minus costs. Simplified: annual value = self-used kWh × electricity price + feed-in kWh × tariff − running costs. Payback = investment ÷ annual value. The result only helps if self-consumption and costs are realistic.
If-then rules
If-then rules for the decision
When usage or prices can change
The main uncertainty is system size, yield, self-consumption, electricity price, cost and export. Show it first as a normal case and then as a cautious counter-case.
When choosing technology or tariffs
If roof orientation, shading, degradation, price trends and financing are unclear, read the result as orientation rather than closure.
When planning the next step
Before a binding decision, result, lever and boundary need to be read in the same scenario.
Step by step
How to interpret this topic
Read demand and generation
The decision starts with: whether the PV system pays off economically and energetically. Only the link to system size, yield, self-consumption, electricity price, cost and export and roof orientation, shading, degradation, price trends and financing makes it robust.
Find the strongest energy lever
The range depends mostly on system size, yield, self-consumption, electricity price, cost and export. A robust case uses assumptions that remain defensible.
Keep model limits realistic
The calculator can name roof orientation, shading, degradation, price trends and financing, but it cannot settle them. They remain part of the next review.
Plan the next energy step
Before deciding, check whether system size, yield, self-consumption, electricity price, cost and export still hold under the limits from roof orientation, shading, degradation, price trends and financing.
Checklist
Quick decision check
- Define the starting question: whether the PV system pays off economically and energetically.
- Vary the main lever within the same scenario: system size, yield, self-consumption, electricity price, cost and export.
- Keep the boundary separate: roof orientation, shading, degradation, price trends and financing.
- Compare base case and cautious case only with the same reference value: whether the PV system pays off economically and energetically.
- Turn the result into action only when system size, yield, self-consumption, electricity price, cost and export and roof orientation, shading, degradation, price trends and financing remain plausible together.
Common mistakes
Common decision mistakes
solar PV: reading the result without context
Without a benchmark, whether the PV system pays off economically and energetically cannot yet lead to a reliable next step.
solar PV: setting the main lever too optimistically
Planning system size, yield, self-consumption, electricity price, cost and export too tightly can understate risk, reserve needs and the next step.
solar PV: overlooking the model boundary
As long as roof orientation, shading, degradation, price trends and financing remain open, the result is guidance rather than a final decision.
FAQ
Frequently asked questions
Does a large PV system always pay off better?
The counter-case shows whether the result can become a stable next step.
Why is feed-in without battery shown separately?
The range between normal case and cautious assumption usually matters more than the single end value.
Should I add a battery immediately?
The calculation creates transparency, but roof orientation, shading, degradation, price trends and financing also decide whether the step really fits.