Path-Q Solar

Should I include a planned heat pump in my electricity-use calculations before choosing a solar system?

Answer

Yes. Include a planned heat pump before final sizing if it is likely to be installed during the system's planning horizon. Its electricity demand can materially change the required system size, especially for heating in cold periods.

Key points

  • Use the proposed heat pump's expected electricity consumption rather than assuming its heating output equals electricity use.
  • Heating demand varies with climate, building insulation, equipment efficiency, thermostat settings, and backup heat.
  • The timing of installation matters; an initial system may otherwise be undersized or need later expansion.

What it depends on

  • Heat-pump type, capacity, and efficiency
  • Climate and heating or cooling load
  • Building insulation and air tightness
  • Use of backup or supplemental heat
  • Expected installation date and future tariff

Risks and trade-offs

  • Forecasts can be uncertain if the building envelope or equipment has not been finalized.
  • Sizing solar for a speculative load can increase cost before the load exists.
  • Seasonal heating demand may not align with peak solar production.

Information you may need

  • Heat-pump model or performance estimate
  • Heating and cooling load assessment
  • Current fuel use and electricity bills
  • Expected installation schedule
  • Plans for backup heat and hot-water electrification

Your next step

What to do next

Obtain a heat-pump electricity estimate and ask for solar scenarios with current load, expected future load, and any planned expansion capacity.

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