Solar Electric System sizing

  • When considering grid-tied solar electric systems, typically the home owner’s budget for the green energy project or the available roof space are the limiting factors in system sizing.
  • For home owners wishing to offset 100% of their annual electricity consumption using a grid-tied system, they can review a previous years electricity bills to estimate annual usage in kWh.
  • As a rule of thumb, divide the annual energy requirement by 1300 to determine the system size in kW required to produce that annual output.
  • Often homeowners will attempt to offset some fraction (50% or 75% for example) of their annual energy using solar electric.
  • Most Rock Paper Sun solar electric installs are designed such that they can be increased in size at a later time.
  • Sizing of off-grid systems is considerably more complex.  Rock Paper Sun can assist with the specifics.   The following must all be considered:

    • Inverter sizing - determine the maximum amount of power required at any instant, or your peak load.
    • Battery sizing - determine your average daily load multiplied by your desired days to run without other energy input.  Having a backup generator can greatly reduce your battery requirements.
    • Solar array sizing - depending on other sources of electricity available, often the solar array is sized to produce 2x to 3x of an average daily energy requirement
    • Reduce your energy load - all sizing directly benefit from reducing your electric load.  Turning off unneeded loads, and using super-efficient appliances will often pay for themselves in energy savings and reduced off-grid system sizing.

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