Path-Q Solar
Will adding an electric water heater materially change my solar system size?
Answer
It may. The effect depends on the heater type, household hot-water demand, incoming water temperature, efficiency, and operating schedule. Estimate the heater's added annual and hourly consumption rather than assuming a fixed increase.
Key points
- A conventional electric resistance heater generally uses more electricity than an efficient heat-pump water heater for similar hot-water service.
- Hot-water use varies with household size, fixtures, temperature settings, and incoming water temperature.
- Scheduling heating during solar-producing hours can improve direct use where practical.
- The solar design should include both energy consumption and any electrical service or circuit requirements.
What it depends on
- Water-heater technology and efficiency
- Household hot-water demand
- Operating schedule and controls
- Existing electrical service and future loads
Risks and trade-offs
- Sizing from nameplate power alone can overstate annual energy use.
- Ignoring recovery cycles and peak operation can miss electrical design requirements.
- A heat-pump water heater may reduce energy use but can have installation, space, noise, or operating constraints.
Information you may need
- Proposed heater type and specifications
- Household size and hot-water usage
- Current water-heating energy source
- Planned operating controls and electrical capacity
Your next step
What to do next
Obtain an annual energy estimate for the proposed heater and ask the solar designer to show its effect on system size, direct use, and electrical service.
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