How to choose a power inverter ?

Solar inverters are an indispensable part of photovoltaic (PV) systems used to power AC appliances. Whether you are camping in the wild, or installed in a truck, RV, boat, or home, or used as an emergency power source during various lightning, floods, and storms, it is very important to understand how to choose the correct inverter size.

Here, we will introduce to you from a professional perspective and provide detailed instructions on determining the size of the inverter.

How to choose the power inverter?

  1. Check the Rated Power of the inverter.

What is the rated power of the power inverter? Normally the manufacturer rate the  power inverter by rated power. For example, for a 1000w power inverter, the rated power is 1000w. There are also a few manufacturer or seller to rate the power inverter by surge power, which is normally double the power of the rated power. For such inverter, it is not full power. Pay attention to it.

The rated powr is the maximum power you can connect the power inverter to your AC load.  It is vital not to connect to power more than the rated power, as it may result in the damage of the power inverter.

  1. What is the DC input voltage?

What is the DC volt input? 12v, 24v or 48v DC volt from battery  is normal in application. For special volt like 36v, 60v,72v 96vdc input, the manufacturer can design and  produce the power inverter as retailed.  Some inverters can handle 600vdc to 1000Vdc, depending on the manufacture for different use of the equipment.  Some inverters can connect to the dc power from solar panel directly, but is it not as stable as connecting to the batteries.  For a higher power input, you can connect to more solar panels in series. The higher the dc volt input, the lower the power losses.

  1. What is the Output Voltage?

The output voltage is the AC power voltage.  It can be single phase or three phase. Normally it is 120v in USA, 230v in europe,240v in Asia. The voltage in different countries is different. Three phase  is normally 380v.  Normally large inverters delivery three phase like 1MW power inverter for industrial use.

  1. What is the frequency?

The operating frequency of an inverter should match the nominal frequency of the AC appliances.  In USA, the frequency is 60hz, in Europe, the frequency is 50hz.  The buyer needs to check the frequency of the AC load.

  1. What kind of socket?

There are differenct kinds of socket in different countries.  There is American type of socket in USA,  Schuko type of socket in Germany, British type of socket in UK, Universal socket in Other countries .  Check what kind of socket you need in your country.

Take an example, Considering the above 5 factors, you can check your AC load power. and tell our customer service staff, you need 3000w,12v dc to 120v ac , 60hz USA type of socket.

  1. DC-AC ratio of the inverter

The DC-AC ratio is the ratio of the difference between the nominal power of the photovoltaic system and the AC output of the inverter. Generally, the DC power input capacity of a solar inverter is slightly higher than its nominal AC output. Therefore, the nominal output of the inverter you want to choose can be slightly lower than the nominal photovoltaic system size.

Installers will divide the required PV system size by their preferred DC to AC ratio, which is usually estimated to be between 1.2 – 1.35. The following table lists some commonly used solar inverters and their maximum DC to AC ratio.

3.How to size your inverter?

1.This formula will help you calculate the daily energy consumption of the load.

2.With the daily energy, we can calculate the DC size of the PV system.

PSH refer to the Peak Sun Hours in your state and a derating factor attached to DC losses and real-world operability for solar panels.

For off-grid applications, a derating factor is 0.6,while a 0.7 factor is intended for grid-tied.

3.Finally, we’ll use the DC to AC ratio of the inverter to calculate the size of your inverter.

By using these three formulas, you can quickly calculate the daily consumption of the required application, the size of the photovoltaic system and the size of the inverter.


For example

Suppose the average daily energy consumption of an RV is as follows:

With this daily consumption, we can calculate the required PV system for the campervan by using Formula (2).

Then, we can cover the usage and size of the inverter by using Formula (3) and the 1.25 DC to AC ratio.

A solar inverter of 508W is the perfect solution for this RV. As such, the most appropriate choice would be a solar inverter between 500W to 600W.


By the way, if you want to buy an inverter quickly, you can directly share the scenario you want to use (including power supply, load) with our customer service staff, and they will recommend the most suitable inverter for you.

Combining the above aspects, you can get the type, specification and size of the inverter you need.

For example, what you need is an off-grid inverter 3000W 12VDC 120VAC 60HZ US PLUG.