Path-Q Solar

Is it better to install the largest system the roof allows or match current electricity use?

Answer

Neither is automatically better. Match the design to credible current and future loads, available roof area, system economics, export treatment, electrical limits, and the value of flexibility. A larger system can help with future electrification, but excess capacity may have lower value if it produces more exports than useful consumption.

Key points

  • Current-use matching is simpler but can miss likely future EV, heating, or appliance loads.
  • Using all available roof space may be sensible when future demand is well supported and the system can be accommodated.
  • Production timing and export terms matter as much as annual energy totals.
  • Compare incremental cost and value for each additional portion of the system.

What it depends on

  • Current and forecast electricity use
  • Roof and electrical capacity
  • Export treatment and import costs
  • Future plans and system expansion options

Risks and trade-offs

  • Oversizing can increase cost and reduce the value of surplus production.
  • Undersizing may require a later expansion that is more expensive or technically limited.
  • The largest roof layout may use less productive or more complex roof areas.

Information you may need

  • Current bills and planned future loads
  • Roof layout and production estimate
  • Incremental system cost by size
  • Export, import, and expansion assumptions

Your next step

What to do next

Compare at least current-load, expected-future-load, and roof-maximum designs using the same production and economic assumptions.

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