Path-Q Solar
Should an electric water heater be included in my solar system design?
Answer
Yes, include an electric water heater if it is on the same account and will operate during the system's life. Estimate its annual energy use and schedule, then assess whether solar can serve it directly or whether storage, controls, or grid energy will be needed.
Key points
- Electric water heating can be a meaningful household load, especially with high occupancy.
- Heat-pump water heaters generally have different consumption characteristics from resistance heaters.
- Operating or preheating during solar-production hours can improve on-site use when practical.
- The heater's peak power can affect electrical and backup-system sizing.
What it depends on
- Water-heater type, capacity, and efficiency
- Hot-water demand and household size
- Operating schedule and control settings
- Whether the heater is included in outage backup
- Electrical service capacity
Risks and trade-offs
- Sizing for a future heater that is not yet selected introduces uncertainty.
- A larger solar array may not eliminate grid use during cloudy periods or nighttime.
- Load-shifting controls can improve solar use but may affect comfort or equipment requirements.
Information you may need
- Current and proposed water-heater specifications
- Electricity or fuel use for hot water
- Household occupancy and hot-water pattern
- Whether backup operation is required
Your next step
What to do next
Provide the proposed water-heater model or estimated annual consumption and ask the designer to show its effect on array, inverter, and backup sizing.
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