Path-Q Solar
How should electric space heating affect the size of solar system I need?
Answer
Include the expected annual electricity use of the heating system in the solar design, along with its seasonal and peak demand. Electric heating can substantially increase consumption, but the amount varies widely by climate, building efficiency, heating type, and thermostat settings.
Key points
- Resistance heating generally uses more electricity per unit of delivered heat than a heat pump, while actual performance depends on equipment and conditions.
- Heating demand is seasonal and may occur when solar production is lower.
- Heat loss, insulation, air sealing, and thermostat settings materially affect consumption.
- Use measured or modeled heating energy rather than assuming the home's total bill scales by a simple percentage.
What it depends on
- Heating technology and rated efficiency
- Climate, home size, insulation, and air leakage
- Indoor temperature settings and occupancy
- Solar production during the heating season
Risks and trade-offs
- Sizing from annual totals alone can hide winter shortfalls.
- Oversizing to cover all heating demand may be constrained by roof area or economics.
- A future heating-system change can invalidate the original load estimate.
Information you may need
- Heating equipment type and capacity
- Heating bills or fuel use and operating history
- Home envelope and climate information
- Any planned efficiency upgrades or equipment replacement
Your next step
What to do next
Give the designer heating-use records or a building-load estimate and request a seasonal production-versus-consumption analysis.
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