Path-Q Solar

Does charging an EV mostly at night reduce the financial value of rooftop solar?

Answer

It can. Night charging usually reduces direct use of solar electricity unless the vehicle charges during daylight or a storage system shifts solar energy to the evening. The financial effect depends on the value of exported electricity, import prices, time-based charges, demand charges where applicable, and whether charging can be scheduled flexibly.

Key points

  • Daytime charging can increase direct solar self-consumption.
  • Night charging may still benefit from solar on an annual basis if exported energy receives meaningful value, but that value is not universal.
  • Managed charging, workplace charging, or storage can change the timing relationship.
  • The EV's charging load can still increase the value of a larger system if its electricity is offset under favorable terms.

What it depends on

  • Utility import and export pricing and any time-based rate structure
  • The household's solar production profile
  • EV charging schedule and ability to shift charging
  • Storage availability, losses, and operating controls

Risks and trade-offs

  • A system sized for annual EV energy may produce exports with lower value than onsite consumption.
  • Storage can improve timing but adds cost, losses, maintenance, and equipment complexity.
  • Changing charging behavior for savings may conflict with vehicle availability or battery-management preferences.

Information you may need

  • Electricity tariff, export-credit terms, and bill structure
  • Hourly or interval load and solar-production estimates
  • EV charging times and flexibility
  • Storage options and costs, if considered

Your next step

What to do next

Compare the financial result for night charging, daytime charging, managed charging, and storage using the applicable current tariff and export rules.

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Some details may depend on your location, installer, utility, incentives, regulations, or specific property.

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