Path-Q Solar
Should I account for backup electric heat when estimating solar needs for a heat pump?
Answer
Yes. Include expected backup or auxiliary electric heat as a separate scenario, especially for cold-weather operation, defrost cycles, startup, or conditions when the heat pump cannot meet the load. Do not assume backup heat will operate continuously unless the system design indicates that it will.
Key points
- Identify whether backup heat is built in, separately installed, or disabled.
- Estimate when it operates and how much power it draws.
- Use cold-weather and high-demand scenarios rather than only average operation.
- Distinguish annual energy from short-duration peak demand, since both can affect design.
What it depends on
- Heat-pump controls and balance point
- Backup heater capacity and operating schedule
- Building heat loss and local weather conditions
- Thermostat settings and occupant behavior
Risks and trade-offs
- Ignoring backup heat can understate winter consumption and electrical capacity needs.
- Sizing solar for a rare extreme event may produce excess annual capacity.
- A battery or inverter may not support the backup heater even if annual solar production is sufficient.
Information you may need
- Heat-pump and backup-heater specifications
- Control settings and expected operating conditions
- Heating load or historical winter consumption
- Whether backup heating is intended for normal or emergency use
Your next step
What to do next
Ask the designer to show annual energy and peak electrical demand with backup heat excluded, expected, and conservatively included.
Path-Q
Find the right next step
Answer a few questions and we’ll narrow your options.
Loading…
SQ01862