solar inverter??

ml2482ml2482 Registered Users Posts: 2
I've noticed some DIY kits can produce X Watts but the solar inverter is rated below the production amount. Take the example below. Total panels can produce 5760 Watts but the kit comes with a 5000 Watt inverter.  Is the inverter sized correctly? 

Grid-Tie Solar Power Kit with 5760 Watts of Panels and 5000 Watt SolarEdge HD-Wave Inverter


  • BB.BB. Super Moderators, Administrators Posts: 30,972 admin
    In general, solar panels produce less power (Power = Volts * Current) than their nameplate rating. As the panels get hot (not freezing weather, full sun on panel), the Vmp (voltage maximum power) drops, and so does the available power.

    And most MPPT based (maximum power point tracking) hardware (solar charge controllers, Grid Tied inverters) are based on buck mode switching power supply designs. These types of power supplies have the ability to limit their maximum power/current throughput to their rated power--So "over paneling" does not hurt or damage these devices.

    Typical over rating is around 1/0.77 to 1/0.75

    We assume that in most conditions, the solar panels will output around 75% to 77% of their rated power a few days/times a year and, in general, very little of the available harvest is "thrown away".

    For a 5,000 Watt GT inverter, we would suggest a maximum (cost effective) over rating of:
    • 5,000 Watt inverter * 1/0.77 panel+controller derating = 6,494 Watt array "cost effective" maximum
    Of course, there is the issue of heat. Electronics do not like heat (or thermal cycling). And many folks will oversize the electronics (vs the size of he array--Say run a 5,000 Watt device at 80% of rated power or ~4,000 Watts) to keep the devices cooler.

    Of course, good ventilation and air circulation is a big help. The engineering rule of thumb is for every 10C/18F increase in temperature, there is a x1/2 reduction in life (and conversely, every drop of 10C/18F is a 2x increase in aging life).

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • ml2482ml2482 Registered Users Posts: 2
    Thanks for the info Bill
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