I designed an inverter with a maximum input voltage of 20 volts.

I want to make a specification of the efficiency of the inverter that I made using the formula efficiency = (output power / input power) * 100%.

  • The problem is I don't know how to calculate the output power of my inverter. Is the output power obtained from the load voltage * the load current connected to the inverter?

  • Is the input power obtained from the input DC voltage * the input DC current?

  • \$\begingroup\$ Do you know how to calculate power the of an AC signal connected to a load? \$\endgroup\$
    – Andy aka
    Sep 27, 2020 at 13:06
  • \$\begingroup\$ I don't know about that. how to calculate it? @Andy aka \$\endgroup\$ Sep 27, 2020 at 13:14
  • \$\begingroup\$ For DC systems it's simply DC voltage multiplied by average (DC) current. For AC systems you need to do instantaneous multiplication and then averaging to get watts. \$\endgroup\$
    – Andy aka
    Sep 27, 2020 at 15:21
  • \$\begingroup\$ It's not clear -at least to me- whether you have a working prototype or simulation and whish to measure achieved efficiency or instead you are going to estimate it analytically \$\endgroup\$
    – carloc
    Sep 27, 2020 at 17:15

1 Answer 1


The simple answer is yes to both questions. However you must calculate the power using a sufficient number of instantaneous values of the output voltage and current and integrating the results. That is necessary to avoid errors due to phase difference between voltage and current and harmonic content. The calculated efficiency will only be valid for the load condition used. If the inverter has forced cooling, you must be sure to include the power required as part of the input power.

  • \$\begingroup\$ what does "sufficient number of instantaneous values of the output voltage and current and integrating the results" mean? \$\endgroup\$ Sep 27, 2020 at 13:17
  • \$\begingroup\$ @NurAqmarina if you have to ask that, how did you manage to “design” an inverter? Or did you just choose one based on size? \$\endgroup\$
    – Solar Mike
    Sep 27, 2020 at 13:44
  • \$\begingroup\$ The sample rate must be high enough to accurately represent the waveform and harmonics encountered. Someone else my have a better answer than that, Integrating the results means integrating the instantaneous values of power over one cycle of the output waveform. \$\endgroup\$
    – user80875
    Sep 27, 2020 at 13:49

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