Path-Q Solar

What should I compare when two installers propose different solar system sizes?

Answer

Compare the assumptions behind each size, not just panel count or price: annual production, shading, consumption, self-use, exports, limits, equipment, degradation, cost, and expected cash flow. A larger system is not automatically better if additional generation is poorly valued or constrained.

Key points

  • Check production per installed capacity and the shading and orientation assumptions.
  • Compare expected on-site use, exports, curtailment, and export compensation.
  • Review panel, inverter, battery, roof-area, warranty, and expansion differences.
  • Test both designs against future loads, lower export value, and utility limits.
  • Compare total installed cost and long-term value, not only annual production.

What it depends on

  • Electricity consumption and future loads
  • Site orientation, roof area, and shading
  • Tariff, export compensation, and interconnection limits
  • Equipment, financing, incentive, and maintenance assumptions

Risks and trade-offs

  • A larger system may produce more energy but lower marginal financial value.
  • A smaller system may leave future loads unmet or require a later retrofit.
  • Different assumptions can make otherwise incomparable payback claims.

Information you may need

  • Both proposals and production models
  • Recent usage and planned electrification
  • Export and interconnection terms
  • Installed prices and financing
  • Equipment and warranty details

Your next step

What to do next

Normalize both proposals to the same usage, tariff, export, degradation, and financing assumptions, then compare the resulting cash flows.

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SQ01470