Path-Q Solar
How will a heat pump change the solar system size I need?
Answer
A heat pump can increase electricity use, so the solar system may need additional capacity if you want to offset that demand. The increase depends on the heat pump type and efficiency, climate, building insulation, existing heating fuel, thermostat settings, and whether the system also provides cooling or hot water.
Key points
- Estimate the heat pump's annual and seasonal electricity use rather than using its maximum electrical rating as annual consumption.
- Heating demand may occur when solar production is lower, creating seasonal imports even with enough annual generation.
- Insulation, air sealing, controls, and equipment sizing can materially change electricity use.
- Include other electrification plans at the same time where reasonably certain.
What it depends on
- Heat pump type, efficiency, and capacity
- Climate and building heat loss
- Current heating fuel and usage
- Operating temperatures and controls
- Solar production and desired offset
Risks and trade-offs
- Actual use can differ substantially from estimates based on equipment labels.
- Oversizing the solar system for uncertain heating demand may reduce financial value.
- A heat pump may change winter demand more than annual totals suggest.
Information you may need
- Proposed heat pump specifications
- Current heating fuel use and costs
- Building efficiency and insulation information
- Expected operating schedule
- Monthly solar production estimate
Your next step
What to do next
Have the HVAC professional estimate annual and monthly electricity use, then ask the solar designer to model that load separately.
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