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Boondocking has never been more convenient as inverters allow you to use appliances with solar power anywhere. To run a microwave though, it is important that you have the right inverter size to match the microwave’s power requirements.
A 1500W pure sine wave inverter is sufficient to run a 700 watt microwave. However, the microwave peak watt rating must be 3000 watts or less.
How to Calculate Microwave Inverter Power Requirements
The formula is microwave watts x number of hours used = inverter size. However you have to factor in the surge watts and running watts to find the right inverter capacity. The surge capacity of an inverter is usually double its running capacity, so a 2000 watt inverter has a 4000 watt surge limit. Their ratings are usually given in running watts, but check to be sure.
Microwaves use anywhere from 800W at the low end up to 3000W. A 1500W system like the Kreger 1500W Power Inverter can handle a microwave with 3000 watt surge and 1500 running watts. A 2000W inverter on the other hand, cannot run a microwave if its running watts exceeds 2000 watts and its surge is over 4000 watts.
If you have an 800W microwave, all it takes is an 800W capacity inverter to run it, right? Well it is not that simple. Microwave surge watts can be double that of its running watts, so an 800 watt inverter must have a peak capacity of 1600 watts. If the surge watts is 3-4 times the running watt, you need an even larger inverter.
Large appliances like refrigerators, AC units and even hot tubs have a starting watt and running watt requirement. The starting or surge watt is the power needed to initialize the appliance. This only takes a second or two then it uses running watts, which is lower.
Three important things to remember. One, when buying a microwave, choose an energy efficient model, second, check the running wattage (found on the manual) and the surge watts. And third, your inverter must be able to support the surge watts.
Factors That Affect Microwave Power Consumption
How much power you actually consume depends on frequency of use. A 1200W microwave uses up 1200W per hour. But if you use it for 30 minutes that is only 600W. And if you use the microwave to reheat food for 15 minutes or so, that is 300W.
This is very important to remember as it applies to all appliances including TVs, AC units, computers, freezers etc. The wattage usage is only a guide because you could end up using way less or much more. If you only use a microwave a few seconds a day to heat water for your coffee, you don’t need a large inverter.
The settings also affect power consumption. Cooking at higher temperatures will require more watts. Even if you have an energy efficient microwave, power usage will go up if the settings are at maximum and you run it for hours.
The quality of the microwave is critical. Some manufacturers are better than others in designing energy efficient appliances. Some microwaves are made for RVs and campers, while others are for homes. You decide which one best suits your needs. Which you choose determines how much energy you have to set aside.
Pure Sine vs. Modified Sine Wave Inverters
Inverters come in two types, pure sine and modified sine. Pure sine inverters are more expensive but offer better power protection and less energy loss. Just like solar panels, inverters lose energy too. Modified sine inverters are more affordable but have limited protection against power fluctuations.
Microwaves and other high powered appliances benefit from a pure sine inverter because they are vulnerable to dangerous power spikes and ebbs. With a pure sine unit you are assured a microwave performs at an optimum level. Modified sine inverters work, but the efficiency level is much lower.
If you are looking for a 1500 watt pure sine wave inverter, we suggest the Power Techon Inverter kit as it comes with all the parts needed to set up the system.
The inverter power requirement given here assumes you will be using it only to run a microwave. You will need a bigger inverter to run other appliances and devices along with the microwave. You can add more solar panels if necessary, or add more batteries. Inverters are built into solar generators so you cannot increase its capacity. However some generators allow you to stack batteries together to boost power.
One more thing to point out. With solar power you can never have too much, and that is true for inverters as well. A 5000W inverter is too much for a microwave, but if you are going to use it to power many appliances, it will be enough. This ultimately depends on how you have set up your home or RV. Generally though it is best to add 20% to your estimated power requirements to be safe.
At the same time you do not want to go overboard. If you only plan to use a microwave and nothing else, there is no point getting a 3000W-5000W inverter. Just one that can handle its wattage is enough. As long as the battery bank is sufficient you will not have problems cooking whatever you want.
What is the Right Battery Bank Size for Microwaves?
A 1000W inverter running a 700W microwave requires a 12V, 150ah battery bank at the minimum. This assumes the surge wattage is 1600W, double the running watts. Increase the battery capacity if the starting wattage is 3 to 4 times higher. As with everything solar if you can get your hands on more batteries the better.
Inverters pull power from the battery bank, so they must be large enough to handle the microwave. If you are on solar power, the solar panel supplies the battery with electricity. The inverter, connected to the battery, converts the power into AC so your microwave can use it. This is how all AC powered appliances work on solar.
Battery capacity is determined in amps and volts. Amps x volts = watts. Most microwaves use 5 amps when in use, but during the initial surge this could be as high as 20 amps. Check the manual for more information on amps used.
You can buy a single battery or multiple batteries, it does not matter as long as the capacity is a match for the inverter and microwave. Use multiple batteries however if you are running the appliances solely on solar panels. It might take several hours for a solar panel to put the required amps in the battery if it is cloudy. The more batteries you have, the faster you can start the microwave.
Tips on How to Run a Microwave with an Inverter
The first tip is to make sure you have the right microwave and inverter match. Here are some of the major points to keep track of.
A 1500W inverter can theoretically run a microwave with a 1500 surge watt load. But in truth, inverters are only 85%-95% efficient. Some energy is lost, similar to how solar cables lose energy when transmitting solar power to appliances. If you have a 1500W microwave, get an 1800W inverter or better. Never push an inverter to the limit as it could damage internal circuits or even the microwave.
- Use the lowest microwave settings whenever possible. You might be surprised how quickly this cooking appliance uses up those watts. If you do not not need to use all its high end features, stick to the basics. This will make a big difference when you compute your monthly power consumption.
- Turn the microwave off when not in use. The standby mode still uses power and over time that will add up. You should do the same with other appliances that run on solar power. This is easy to forget given how miniscule the power used is. But add those up and in a year you might be shocked at how much energy was wasted.
- Look for the most energy efficient microwave possible. Your RV might have one built in, but how efficient is it? You will pay more to buy a new one, but if the difference is watts is large, it may be worth it. This all comes down to how frequent you will use it.
Microwaves have become more energy efficient so they are now suitable for RVs and even camping. With the right combination of batteries and inverter, you will have no trouble firing up that microwave and start cooking.