Inverter efficiency and input voltage

Efficiency of Inverters The efficiency of an inverter indicates how much DC power is converted to AC power. Some of the power can be lost as heat, and also some stand-by power is consumed for keeping the inverter in powered mode.

In general, the efficiency of a PV inverter is a function of the input power and input voltage, with a typical set of efficiency curves being shown in Fig. 1.4. At medium to high light levels and therefore input power from the array, the inverter has a high efficiency, generally well in excess of 90%.

It depends mainly on the power and can also be a function of the input voltage. In PVsyst there are 4 ways of defining the efficiency of inverters : from a set of 3 efficiency curves eff = f (Power, input voltage), all of them automatically built from the Maximum, EURO or CEC efficiencies and Pthresh.

Often, inverter rated efficiency is the primary factor used to determine system performance, but this can be misleading. Efficiency changes with DC input voltage, AC output voltage, the percentage of rated load supplied, and other factors.

So less energy is output than is input. In fact, inverter efficiency can vary dramatically between products, on average it is between 85% and 95%. For example, if you have an inverter with 85% efficiency it means only 85% of your battery power is being sent to your appliances. The other 15% is lost/used up in the inverter.

Inverters can have better efficiency at a higher voltage because the current is reduced and therefore voltage drop and heat are reduced. Inverter input voltage depends on input from batteries or sources such as PV arrays or wind turbines.