Path-Q Solar

How should solar sizing account for a planned home addition?

Answer

Estimate the addition's incremental electricity use and include it in a future-load scenario if the project is sufficiently defined. Account for new heating, cooling, lighting, appliances, and occupancy rather than sizing only from the existing home's bills.

Key points

  • An addition may increase both annual consumption and peak electrical demand.
  • New heating and cooling loads can matter more than lighting or small appliances.
  • If the addition will use a different fuel or equipment, its electric impact may be limited or substantial.
  • The design should distinguish confirmed plans from speculative future use.

What it depends on

  • Addition size, insulation, windows, and occupancy
  • Heating, cooling, water-heating, and appliance choices
  • Construction timing and whether the solar installation precedes it
  • Available roof area and electrical capacity

Risks and trade-offs

  • Sizing too early can miss later equipment choices or building changes.
  • Sizing for an uncertain addition can create excess capacity or cost.
  • Roof changes may affect panel layout, shading, wiring, and future expansion.

Information you may need

  • Addition plans and expected completion date
  • Planned appliances and mechanical systems
  • Expected occupancy and usage pattern
  • Roof and electrical plans for the completed home

Your next step

What to do next

Have the solar designer model the existing home and the completed-home load, using the addition's plans and planned equipment.

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