Path-Q Solar

How should I estimate electricity use if my current home is only partly occupied?

Answer

Do not size solely from a partly occupied period. Use the longest reliable history available, identify which loads and occupants are missing, and create a reasoned estimate of normal occupancy while separating temporary and permanent changes.

Key points

  • Use bills or interval data covering different seasons whenever possible.
  • Adjust for absent occupants, unused rooms, heating and cooling, water heating, appliances, and other loads that will change.
  • If the occupancy change is temporary, treat the current usage as an atypical sample rather than a new baseline.
  • Model confirmed future loads separately instead of hiding them in an unexplained adjustment.

What it depends on

  • Length and seasonality of available usage history
  • Expected occupancy and behavior
  • Heating, cooling, water heating, and appliance types
  • Planned changes to the home

Risks and trade-offs

  • Sizing from low temporary usage can undersize the system for normal occupancy.
  • Overestimating future occupancy can increase upfront cost and unused production.
  • Behavior-based estimates are uncertain and should be tested against comparable historical periods.

Information you may need

  • At least several months of bills or interval data
  • Expected occupancy schedule
  • Major electric loads and their operating patterns
  • Planned changes such as EV charging, heating, or additions

Your next step

What to do next

Prepare a baseline using available seasonal data, then ask the designer for low, expected, and high-occupancy sizing scenarios.

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