Path-Q Solar
How should panel efficiency be evaluated when two systems produce the same annual electricity?
Answer
If two systems truly produce the same annual electricity, compare total installed cost, usable roof area, system size, degradation assumptions, equipment quality, warranties, maintenance, and how production is distributed through the year. Higher panel efficiency alone does not make one system better.
Key points
- Efficiency matters mainly when roof space or layout is constrained.
- Compare modeled monthly and hourly production, not only annual totals.
- Evaluate whether one design uses fewer panels, less racking, or simpler wiring.
- Check that the production estimates use comparable shading, orientation, weather, and loss assumptions.
What it depends on
- Roof-space constraints
- Installed price and equipment count
- Production-model assumptions
- Panel and inverter warranties
- Expected future loads and expansion needs
Risks and trade-offs
- A higher-efficiency system may cost more without delivering more useful energy.
- Equal annual output can hide different seasonal or daytime production profiles.
- A lower-panel-count design may not have lower total installation cost.
Information you may need
- Complete proposals and production models
- Panel dimensions, ratings, and degradation assumptions
- Monthly production and loss assumptions
- Installed cost and warranty terms
Your next step
What to do next
Normalize both proposals to the same assumptions and compare cost per expected kWh, monthly output, roof usage, equipment count, and warranty coverage.
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SQ00277