How do you select an inverter to use with a solar array?

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We offer a wide range of models sizes, brands, as well as models for inverters. There are a variety of options offered. The decision of which is the most appropriate from a lengthy list can be quite a task. There isn’t a “best” inverter for all reasons – what is ideal for an ambulance may not work in an RV. The power output is typically the primary factor, however, there are many other aspects to consider.

There are many aspects that influence the selection of the right inverter (and alternatives) to suit your needs particularly when you move into the larger power ranges (800 or higher). This page should provide all the details you require to narrow down your choices to the best option for your needs.

We provide traditional residential and light commercial inverters and mobile / marine and RV inverters.

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Some Basics First…


The power of the watt is often confused. Watts are simply an indicator of the amount of power a device consumes or produces when it is turned on. A watt is a watt; there’s no such thing as “watts per hour”, or “watts per day”. If something draws 100 watts, it is just what it is: the voltage multiplied by amps. When it is drawing 10 amps with 12 Volts, or one amp when 120 volts are used, it’s at 120 watts. A Watt is defined as a Joule per second. So the expression “watts per hour” is equivalent to the phrase “miles per hour per day”.


A Watt-hour (or Kilowatt Hour, kWh) is the sum of watts divided by how many hours it is used for. It is the term that most people mean when they talk about “watts per day”. If a light consumes 100 watts and remains on for nine hours, that’s 990 watt-hours. If a microwave is powered by 1500 watts and is running over 10 minutes that’s 1/6th of an hour x 1500 which is 250 WH. If you purchase power from your utility (look at the last bill you paid) they offer it to you at an amount of kWh. A kWh refers to a “kilowatt-hour”, or 1000 Watts for an hour (or 1 one watt for every 1,000 hours).


An amp is a measurement of electric current currently. (Amps are not measured with “amps per hour” or “amps per day” either). Amps are crucial because it determines the type of wire you will require, specifically for a low voltage (low tension) aspect of an inverter. Wires are all conductive, and the amps flowing through a wire create heat. If your wire is small to handle the amps required, you’ll end up with hot wires. There is also low voltage in your wire when it’s not big enough. This isn’t an issue. The definition of amps is one Coulombs/second.

The term Coulomb represents the amount of 6.24 10. 18 electrons. Thus 1 Amp corresponds in charge to 6.24 10. 18 electrons that pass through the point of an electrical circuit in one second.

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Amp-hours (usually abbreviated by “AH”) is the term most people are referring to when they say “amps per hour” etc. Amps divided by time = AH. They are crucial because it is the most important measurement of battery capacity. Since most inverters operate from batteries, the capacity is the measure of how long they can run. Visit our page on batteries for more information.

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Watts – Or What Size Power Inverter Do I Need?

Peak Power vs Typical or Average

Inverters must meet two demands in order to meet two needs – Peak power, or surge power, and usual or normal power.

Surge is the maximum amount of power that an inverter is able to provide generally for an indefinite period of time, ranging from just a few seconds to 15 minutes or less. Certain appliances, specifically ones with electric motors require a higher initial surge than when they are running. Pumps are the most frequent instance – another is fridges (compressors).

“typical” is the level of information that the inverter is required to provide on a continuous basis. It is, in essence, an inverter’s constant rating. It is typically less than that of the surge. This could be the amount a refrigerator draws within the first few seconds it takes the motor to kick in how long it takes to run a microwave, or what the total of all these loads adds up to. (See our notes on the power of appliances and/or name tag ratings at the bottom of this article).

The average power is usually lower than normal or surge, and isn’t usually an element to consider when selecting an inverter. If you have an inverter for 20 minutes and a small television for 20 minutes over the course of a single hour then the average could be just 300 watts even though the pump needs 2000 watts. Average power is useful for estimating the capacity of batteries. Inverters should be designed to accommodate the highest peak load as well as for the normal continuous load.