Path-Q Solar

How should solar be sized for a home that may switch from gas heating to electric heating?

Answer

Model the future electrical load rather than sizing from current electricity bills alone. Estimate the heating system's annual and seasonal electricity use, subtract any gas equipment that will be removed, and evaluate whether the roof, inverter, service, and budget can support the resulting increase. A staged design may be appropriate if the conversion timing is uncertain.

Key points

  • Use building heat-loss estimates and the proposed electric system's performance, not a simple one-for-one conversion from gas fuel units.
  • Include auxiliary or resistance heat, cold-weather performance, and any associated electric equipment.
  • Consider other planned electrification, such as water heating, cooking, or vehicles, at the same time.
  • Compare full future sizing with a smaller initial system and a defined expansion path.

What it depends on

  • Current gas consumption and existing heating efficiency
  • Proposed electric heating technology and capacity
  • Building envelope and climate
  • Timing of the conversion
  • Roof, inverter, service, and interconnection limits

Risks and trade-offs

  • Sizing to current usage can leave the system too small after electrification.
  • Sizing for a conversion that never occurs can increase upfront cost and reduce use of the available capacity.
  • Winter heating demand may not align with solar production, so full annual offset does not guarantee low winter bills.

Information you may need

  • At least one year of gas use if available
  • Proposed heating equipment specifications
  • Building heat-loss or efficiency information
  • Other planned electric loads
  • Physical and electrical limits of the property

Your next step

What to do next

Request two designs—current load and post-conversion load—with assumptions, annual production, seasonal energy balance, and expansion constraints shown separately.

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