Path-Q Solar
How does adding a heat pump change the solar system size I should consider?
Answer
A heat pump can increase the solar capacity worth considering because it adds electricity use, but the increase should be based on modeled or measured annual and seasonal consumption. Its actual demand depends on heating and cooling loads, equipment efficiency, climate, and backup-heating operation.
Key points
- A heat pump may replace other fuels while increasing electric consumption.
- Heating and cooling demand can occur in different seasons and at different times of day.
- Backup resistance heat, if present, can materially increase peak and annual electricity use.
- Envelope improvements can reduce the added load and may affect the best solar size.
What it depends on
- Heat-pump type, capacity, and efficiency
- Climate and home heating and cooling loads
- Backup-heating strategy
- Existing fuel use and planned operating settings
Risks and trade-offs
- Sizing from equipment nameplate capacity alone can be misleading.
- A solar system sized for modeled heat-pump use may be oversized if the home is later improved or settings change.
- Annual solar coverage may not match the heat pump's highest-demand hours or season.
Information you may need
- Heat-pump specifications and installation plan
- Existing heating and cooling energy use
- Home envelope and climate information
- Expected backup-heat operation
Your next step
What to do next
Obtain a heat-pump energy estimate and have the solar designer compare current-load and post-installation-load system scenarios.
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