Path-Q Solar

How should I estimate future electricity use for solar sizing if another person will move into my home?

Answer

Start with the home's current normalized usage, then estimate the additional person's effect on occupancy, hot water, heating and cooling, appliances, laundry, and transportation. Use a range rather than a single unsupported number, because behavior and equipment determine the actual increase.

Key points

  • The added demand may be modest or substantial depending on whether the person works or studies at home and uses electric heating, cooling, or appliances.
  • Existing household usage should be adjusted for seasonality and unusual periods first.
  • If the move-in is soon and expected to be permanent, include the estimate in the design; otherwise compare expansion-ready options.
  • Planned EV charging, electric water heating, or other equipment should be modeled separately.

What it depends on

  • Occupancy schedule and work-from-home pattern
  • Heating, cooling, and water-heating equipment
  • Household behavior and appliance use
  • Timing and permanence of the move

Risks and trade-offs

  • Per-person averages can be misleading because homes have shared and fixed loads.
  • Overestimating demand can increase cost; underestimating it can reduce future offset.
  • A future occupant's behavior may differ materially from the current household.

Information you may need

  • Normalized monthly usage
  • Expected occupancy and daytime schedule
  • Major electric loads and planned equipment
  • Move-in timing and expected duration

Your next step

What to do next

Create low, expected, and high future-use scenarios and ask the designer to show the system size and savings under each.

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SQ00676