Off-the-Grid: How Many Watts and Amps Does a Microwave Use?

Microwave ovens are very popular kitchen appliances commonly used for cooking and/or heating food and beverages. Microwave ovens are also very efficient devices, which is very important in many ways.

Due to their convenient nature, microwave ovens are commonly used when camping, on boats, in the RVs, and similar, leading many people to ask themselves, how many watts do their microwave ovens actually use?

Updated: September 4, 2023.

Microwave Ovens - Features and Power Requirements

Most popular microwave ovens range from 500 to 800 watts for compact models and from 800 to 1800 watts for medium to large models, with an average home microwave oven requiring around 1200-1300 watts of power.

In order to find out how many watts your microwave actually needs, check the label on the back/lower side of the microwave - sometimes, there is a slight mismatch between the unit's label (on the front) and the actual wattage requirement.

When being off-the-grid (camping, fishing, hunting, in emergencies, etc.), having a working microwave can be of great help - it can be used for reheating, defrosting, and even cooking and having warm meals, tea, soup, or some other beverage can make a real difference.

When there is no mains power present, there are several options available for running the microwave oven in off-the-grid situations, including:

• portable power stations,
• deep cycle battery combined with a good power inverter,
• power generators.

Best of all, even if your power source is 'weaker' than your microwave oven, keep in mind that some microwave ovens come with different power settings (usually 5-10 power levels, sometimes even more), allowing the user to increase the power gradually.

When the power level of your microwave oven reaches the maximum power of your power source, decrease it a little bit, and feel free to use your microwave while monitoring the power and energy levels of your power source.

Note: most microwave ovens feature only a timer, without the option of setting the power.

Of course, this should be avoided, if possible, and a properly dimensioned power source should be used to power microwave ovens.

How Many Amps Does a 1200-Watt Microwave Use?

1200 watts is the average power level of a regular kitchen microwave oven.

When being powered by 120V, such microwaves use ~10 Amps - using a Ohm's Law it is very easy to calculate the required current:

I(A) = P(W) / U(V) = 1200W / 120V = 10A

Note: we say '~10 Amps' since the nominal voltage of the grid varies a little bit, and when a power inverter or power generator is powering such microwave oven, the voltage can vary even more.

But keep in mind that a 1200-watt microwave uses 10 Amps @120 volts.

Power Inverter + Deep Cycle Battery

To power such a microwave at full power, a 2000-watt power inverter combined with a deep-cycle battery is recommended.

With an average power inverter efficiency of 85%, the battery must be able to provide ~1410 watts:

1200 Watts / 0.85 = ~1410 Watts

If a 12V battery must provide ~1410 Watts, that means that the battery must provide (Ohm's Law again):

I(A) = P(W) / U(V) = 1410W / 12V = 117.5A

And that is a lot of current.

Such power levels are able to provide large lead-acid batteries (12V 100Ah, or more), some of them belonging to group 31, and 4D, 6D, and 8D battery groups.

Since lithium deep cycle batteries usually feature a maximum continuous current of ~1C, one should use a 12V 200Ah or larger lithium battery to power a microwave oven via a power inverter.

Portable Power Generator

Portable power generators are used for powering various tools and appliances, microwave ovens included.

Again, 2000W units are recommended for powering 1200-watt microwaves - such load (~60% of the maximum running watts) will not cause operating issues for most power generators in this class.

Also, such units feature fuel tanks large enough to operate for hours under such load.

When choosing a power generator for microwave ovens and other appliances, go for models with low Total Harmonic Disorder (THD) levels, preferably ≤3% - such units can power even sensitive electronics.

Note: after the microwave oven is turned off, if there are no other appliances or loads, be sure to turn the power generators off to conserve the fuel. Also, power generators must operate outdoors to prevent the buildup of toxic gasses and fumes, Carbon Monoxide (C) included.

Solar Generator/Power Station

Solar generators/power stations allow the user to power microwave ovens indoors without the dangers of toxic fumes and gasses and with almost no noise.

For powering 1200W microwaves, a 2000W (4000W peak) solar generator is recommended - it may sound like an overkill, but such units are strong and robust enough to power even larger microwave ovens, but also a few other smaller loads

Smaller portable power stations are able to power even the larger microwave ovens if the output power of the microwave oven is decreased - just be prepared for a few alarms and popped-out circuit breakers when finding the 'sweet spot.' However, this should be avoided if possible.

 How Much Energy Microwave Ovens Need

Total consumed energy depends on how long microwave is going to be used and its wattage. For example:

• 1200W, 1 minute (60s): E(J) = P(W) * T(s) = 72 kJ = 20 Wh
• 1200W, 2 minutes (120s): E(J) = P(W) * T(s) = 144 kJ = 40 Wh
• 1200W, 5 minutes (300s): E(J) = P(W) * T(s) = 360 kJ = 100 Wh
• 1200W, 10 minutes (600s): E(J) = P(W) * T(s) = 720 kJ = 200 Wh

(To convert kJ into Wh, we need to divide with 3.6.)

Obviously, the largest "energy issue" have solar generators/power stations due to their relatively small and compact built-in batteries.

However, solar generators that feature outputs in the 2000W range usually store up to, or even more than, 2000Wh of energy in their high-energy lithium batteries.

So, if we have a 2000Wh power station that also features internal 90% energy efficiency, such a power station will be able to run a 1200W microwave oven for 10 minutes:

N = E_PS(Wh) / E_microwave(Wh) * 0.9 = 2000Wh / 200Wh * 0.9 = 9 times

Power inverter + deep cycle battery combo and especially power generators will be able to run a microwave oven much longer/more times.