Solar longest and shortest days

Discussion in 'Environmental Discussion' started by bwilson4web, Jan 1, 2026 at 12:08 AM.

  1. bwilson4web

    bwilson4web BMW i3 and Model 3

    Joined:
    Nov 25, 2005
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    Location:
    Huntsville AL
    Vehicle:
    2018 Tesla Model 3
    Model:
    Prime Plus
    Looking at Solar, Grid, and House Load for the Summer Solstice June 20, 2025 and Winter Solstice December 21, 2025. Looking at a month gives a 30-31 day sample for each month.

    SOLAR

    Solar_Jun_Dec.jpg
    • 460.7 kWh vs 222.7 kWh - 683.4 kWh
      • 67.4% = 460.7 / 683.4
      • 32.6% = 222.8 / 683.4
    • Longest Summer is ~2x the Shortest Winter (including one extra day)
    GRID

    Grid_Jun_Dec.jpg
    • 195 kWh vs 603.5 kWh - 798.5 kWh
      • 24.4% = 195/798.5
      • 75.6% = 603.5/798.5
    • About a 3 to 1 ratio in grid power needed in winter
    • An extended power outage required 2.3 kWh from the emergency generator
    • Grid electrons cost ~$0.12 / kWh
    HOUSE LOAD

    House_Jun_Dec.jpg

    • 883.4 kWh vs 947.7 kWh - almost identical electrical load June or December

    CONCLUSION

    The Summer or Winter electrical loads were nearly identical. The solar production significantly avoided grid load in the Summer and still helped in the Winter. This suggests that adding roof-top, wind powered generator(s) might significantly improve year round performance.

    Bob Wilson