May 23

Microwave Wattage Input or Output | Which of the Two Matters & Why?


Author: Colin Ma and its partners may earn a commission if you purchase a product through one of our links.

When you look at the specifications of a typical microwave oven, you will realize that it has two different wattage ratings i.e input wattage and output wattage. So which microwave wattage input or output matters when choosing.

In short, both wattage ratings matter. The input wattage of the microwave oven pertains to the electrical circuit design and circuit requirements for the microwave oven, whereas the output wattage of the microwave pertains to how powerful it is for microwave cooking and heating.

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As a customer, you need to be well versed in both of these ratings when looking for a microwave. There are many important aspects that you can tell about the microwave just by looking at its two wattage ratings.

In this article, we will discuss in detail both of these ratings and explain why they are important.

Microwave Wattage Input or Output

As mentioned earlier, both input and output wattage ratings are equally important. However, they both relate to different characteristics.

Let us break both of them down here.

What is Microwave Input Wattage?

Microwave ovens input wattage is the power that the appliance draws from the wall socket.

Input power is basically the cooking power required by the microwave top operation. Therefore, whether you are connecting it to your home grid, UPS, or a generator, you have to make sure the microwave is being fed the stipulated amount of input wattage. Otherwise, the microwave may malfunction.

The other important consideration is that it pertains to the amount of current the microwave will draw from the wall. This dictates your cabling and your electrical protection as discussed below.

Why Input Wattage Matters?

There are three very important reasons why input wattage matters and they all pertain to the electrical design.

Circuit Design

30 amp circuit breaker
A Typical 30 Amp Circuit Breaker. The breaker size is chosen based on the circuit requirement taken from the INPUT WATTAGE of the connected devices.

The first important consideration is the circuit design.

The circuit, the cabling, the breaker, or the fuse installed are all based on the input electrical energy rating of a device.

When you see a microwave oven with an input wattage of 1500 watts but an output power of 1000 watts, you will take the input electric energy when considering the size of the breaker, the size of the fuse, and the gauge (diameter) of the cables.

Looking a the simple formula, where the voltage is either 120 or 220 volts depending on where you live (the US uses 120 Volts standard), we can calculate the Amps.

Microwave Wattage Input or Output

A 1500W Input Power pertains to 12.5 Amperes and a 1200W Output pertains to 8.5 Amperes (at 120 Volts). However, when designing the circuit, you will have to base it on 12.5 Amperes (Input Current) and NOT on the 8.5 Amps (Output Current)

All breakers have a certain Amperage rating beyond which the circuit will trip. According to US standards, breakers should be used at a maximum of 80% of their rating IF the devices are connected to a receptacle/socket. However, the usage should not exceed 50% of the breaker rating IF the device is fastened or affixed like an over-the-range microwave.

In short, a countertop microwave oven that has an input current rating of 1500W, with a corresponding input amperage rating of 12.5 Amps and connected to a receptacle, should be connected to a breaker that is 16 Amps or higher in rating (80% of 16 Amps is roughly 12.5 Amps).

Another important consideration is cabling. Since the input current relates to the input current rating, it helps in choosing the right wire gauge as discussed below:

Extension Cable

Wiring Guage
Source: 3DM

Although a large appliance is not recommended to be used on extension cables, if you absolutely have to, the input wattage rating and the corresponding input current rating matters a lot.

We have already established that input current directly relates to the input current above.

When choosing an extension cable, you have to make certain that the wire gauge or diameter of the extension cable is large enough to support the rated input current.

For instance, a microwave oven with an input current of 1500W operating at 120 Volts has an amperage of 12.5 Amps. Hence to SAFELY operate this oven over an extension cable, you will need to have at least a 16 Gauge Wire.


When it comes to billing, the power consumption is based on the input current rating and not on the output power rating.

In other words, a microwave that has an input current rating of 1500W and output wattage of 1000W would be billed based on the 1500W rating.

What is Microwave Output Wattage?

The output wattage is the power of the Microwave Energy that the oven supplies to the food.

Why are Input and Output Wattage Different?

Basically, when it comes to energy conversion, no device is 100% energy efficient.

There are losses.

Take the engine of a car, as an instance, it does not convert 100% of the fuel energy into workable energy. Instead, most of it is lost as heat.

Similarly, when input current is delivered to the Magnetron Assembly (The component that produces the Microwaves), a lot of the energy is lost before being converted to the Microwaves.

A typical basic microwave oven has an efficiency of about 65%. Meaning only 65% of the input current is transformed into microwave power for heating the food.

Why Output Wattage Matters?

The output wattage matters to you as a typical buyer. It tells you a lot about the quality of the microwave.

The higher the power of a microwave, the more heavy-duty it is considered.

Heating Power

As mentioned earlier, the output power pertains to the strength of the microwaves generated.

A high output power means that your food will be heated quickly and consistently.

If you notice that sometimes the food in your microwave oven is not heated properly, especially the portion found at the bottom of the bowl, then the power of the microwave can be blamed.

A higher-powered microwave penetrates the food better and also allows you to speed up the heating process.

The following are the typical output wattage rating for home microwaves.

  • Low-Powered:  700W – 900W
  • Medium-Powered: 1000W – 1100W
  • High-Powered: 1200W and beyond


The higher the output power of a microwave, the higher the cost GENERALLY.

This is typical because high-powered microwaves are generally more durable and larger than low-powered 900-watt models.

Typical Input Wattage and the Corresponding Output Wattage

The following should give you a rough idea about the typical input current as well as its corresponding output power in microwaves.

Taking a typical efficiency of 65% we get:

  • 1100 W Input – 700 W Output
  • 1350 W Input – 900 W Output
  • 1700 W Input – 1100 W Output

It should be noted that the figures above are just a rough estimation. We have taken a 65% efficiency. However, in reality, the efficiency can differ greatly from model to model.

Final Words

Here we learned comprehensively about the microwave power rating. We particularly talked about which microwave wattage input or output matters and for what.

Simply put, both of these ratings are very important in their own regards. One sheds light on the circuit design, and power consumption and the other tells you about how well and quickly it will heat up the food.

Here we took rough estimates of power rating to just give you an idea. The actual ratings can be found on the appliance itself or inside the appliance manual. If you cannot find the wattage ratings, it is advisable to talk to the customer service of the manufacturer.


1. How do I know the output wattage of my microwave oven?

The wattage of the oven can be found on the inside of the door, on the serial number plate on the back of the oven, or in the owner's handbook or on the manufacturer's website. To determine the wattage, use a Time-to-Boil Test: In a 2-cup glass measure, measure 1 cup (8 fluid ounces) of water.

2. Is rated power input or output?

The rated power of an electrical or electronic appliance is specified on the appliance. This is referred to as the Input Power. The term Input Power refers to the amount of power required by an appliance at its input, i.e., from the plug point. The term power at the load refers to the amount of energy that an appliance can deliver.

3. What size breaker do I need for a 1500 watt microwave?

 A microwave oven with that much electricity will require a 30-amp circuit. Additionally, a microwave oven rated at 1,500 watts will consume around 2,550 watts when operating at maximum capacity.

4. What is power output in microwave oven?

Microwaves are typically rated between 600 and 1,500 watts. Higher wattage produces more heat, while a lower wattage results in a longer microwave cooking time. Small ovens normally have a power wattage of 600–800 watts, while medium-sized ovens have a power output of 900–1,200 watts. Larger ovens can have a power wattage of up to 1,650 watts.

5. How many amps does a 700 watt microwave draw?

A 700 watt microwave will typically draw about 5 amps. The wattage is calculated by multiplying the current (in amps) by the voltage. Divide the amount of watts by the voltage to obtain the current, which is expressed in amperes. 700W/120V=5.83Amps

Our Recommended Microwave Oven

  • It has ten power levels with multi-stage cooking
  • Ideal small-space solution
  • Easy-to-view interior lighting

About the author

Colin Ma

An avid home chef, Colin is equally passionate about delicious meals as well as the latest cooking appliances. He's also a keen writer about cooking-related topics.


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  1. Microwave input 1500w—output 1000w. however using the recommended
    cooking time on a package the food is alway overcooked????
    GE microwave.

  2. Why would a homemade cotton sleeve to bake potatoes in start flaming in 3 minutes in my new 1000w microwave..2 different types did..but always cooked for 8min in my older 1000 w microwave with no problem?

  3. “There are loses.” typo

    also, when cooking a frozen dinner and it mentions a wattage, is that the input or the output?

  4. What is the answer to this question, i would like to know., the article is too complicated, all i want to know is the answer to this question

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