Path-Q Solar

Should solar quotes use the same electricity-use assumptions to be comparable?

Answer

Yes. Quotes should use the same historical or agreed electricity-use baseline, future-use assumptions, production method, and treatment of export or bill credits. If assumptions differ, compare the underlying loads and production separately rather than relying on each quote's savings figure.

Key points

  • Provide each installer with the same utility bills or interval data when available.
  • Separate current consumption from expected changes such as electrification, an addition, or an electric vehicle.
  • Compare modeled production, system losses, shading assumptions, degradation, and usable storage.
  • Check whether savings calculations use the same rates, fixed charges, export treatment, and escalation assumptions.

What it depends on

  • The quality and time span of the electricity-use data
  • Expected changes in household load
  • The applicable bill structure and export rules

Risks and trade-offs

  • Using inflated future consumption can oversize the system and overstate savings.
  • Using only past use can undersize a system if major loads will be added.
  • Different bill assumptions can make identical systems appear to have very different financial results.

Information you may need

  • Recent utility bills or interval consumption data
  • Planned changes to electricity use
  • Each quote's production, rate, export, and degradation assumptions

Your next step

What to do next

Give all installers the same load profile and request a side-by-side output and savings calculation using clearly stated assumptions.

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SQ01479