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Having a microwave just makes food preparation so much easier, so no wonder it is a fixture in homes and RVs. But it does use a lot of power, so how many batteries will you need? That is what this guide is for, to give you an in-depth guide on how many batteries are needed to run a microwave.
A regular microwave uses 800 to 1500 watts or up to 130 amps. But if you factor in inverter inefficiency, which can be up to 15%, you are looking at a 150 amp draw. You should get a 250ah deep cycle battery to run a microwave.
Microwave Battery Power Requirements
Microwaves come in all shapes and sizes, but they generally fall into two types, regular and compact microwaves. Regular sized models require 1000 to 1500 watts to run, while compact models run on 700-800 watts.
The calculation is simple:
Microwave watts / battery volts = amps
Amps = required battery size
Battery capacity is measured in amps, so the first thing you have to do is convert watts to amps as described above. If you have a 1500 microwave for example:
1500 watts / 12V = 125 amps
That is 125 amps, but because inverters are not fully efficient, a 200ah or 250ah battery is more appropriate. When it comes to batteries and solar power in general, you can never have too much power.
The watts used by a microwave also depends on the settings and how long it runs. Run a 1500 watt microwave for an hour and that is what it consumes, 1500 watts or 125 to 150 amps, depending on the inverter efficiency rating.
A good choice would be he Mighty Max 250ah 12V SLA battery. This is enough to run the microwave and does not need as much maintenance as other batreies.
But most of us use it for just a few minutes to heat food, so wattage will be lower. An 800 watt 12V microwave running at full heat for 15 minutes will draw 25-35 amps.
If a microwave uses only 35 amps an hour, why should you get a 250ah battery? That is because microwaves use a lot of power to start up. Batteries also lose charge faster when more amps are pulled, so reserve power is recommended.
Running Watts and Starting Watts Explained
Just like a refrigerator, the starting watts required by microwaves are sometimes twice its running watts. A 1200 watt microwave might need 2000 to 2400 watts to start before running at 1200 watts, for example.
You should always check the specs to be certain. But it is better to overestimate the battery requirements, so assume that a 1500 watt microwave needs 3000 watts to start or 125 amps.
The starting watts is only for a second or less, but it could pull a lot of power from the battery. Keep that in mind especially if you have a deep cycle battery that requires a 50% depth discharge. However this probably will not be an issue if you only use the device for a few a minutes a day.
Do all microwaves have high starting wattage? Most regular models do, but portable units may not. A 700 watt microwave for instance, may only require 1000 starting watts or so. But it is better to have more battery power in case of a power surge.
Even if the starting watts lasts for only a second, the battery must be able to supply the power. Will it completely drain your system? Unlikely, but we strongly suggest to have a high capacity battery just in case.
Not all appliances have starting watt requirements, but large ones like refrigerators and air conditioners do. Motors, power tools and air compressors also have high surge watts.
Which Type of Battery Should I Use?
There is another reason to use a high capacity battery. The more amps are drawn, the faster the charge wears down. Running a microwave every day even for a few minutes can take its toll on the battery.
A 1200 watt microwave needs a 250ah AGM battery minimum. Most AGM batteries have a 70% DOD so there should enough power available. With a lithium battery you can discharge it down to 90% or even 100%.
Microwaves and other appliances like hair dryers run fine on lead acid batteries. Unless you need the longer discharge rate by lithium, lead acid batteries will be fine.
6V or 12V Batteries. A 6 volt battery usually produces more amps than a 12V, so connecting two 6V batteries in a series is better than a single 12V battery. However, 12V batteries are getting better all the time so the difference between them is getting smaller.
To keep calculations simple, remember the following.
- Microwave starting wattage is often twice its running wattage.
- Your battery capacity should be higher than what is required. If your microwave needs 150 amps, a 250 or 275ah capacity is ideal. It is always better to have more power than less.
- The running wattage refers to hourly usage. If you just heat food for a few minutes the power consumption will be lower.
- Lithium batteries can cost twice as much as lead acid. If you run a lot of heavy duty appliances, tools and devices, lithium is recommended. But for most RVers, deep cycle lead acid batteries are sufficient.
The battery size given here can run most microwaves. But it assumes you will not run another heavy load. If you have a heater hooked up to your solar inverter for instance, that will require much more battery power.
Microwaves need an inverter to run, and in most cases you have to use pure sine. Pure sine wave inverters can supply more battery power to appliances rather than modified sine. It costs more true, but you get the best possible results.
What Inverter Size Do I Need?
Inverters support different types of batteries from 12V, 24V and up. If your system only supports 24V, you can connect 6V or 12V batteries in a series to increase the voltage up to 24V or higher. Always check the inverter specs to ensure compatibility.
Inverter comes in various sizes, from portable 1200W systems to 5000 watts and higher. Since microwave capacity is in watts you can determine if they are compatible. Now you just need to convert battery amps to watts (amps x volts = watts) and you are set.
If you have a solar power system, chances are you already have an inverter. A 3000 watt system should be enough to run any microwave. If you are in the process of setting one up, calculate how much power your microwave will use and every appliance you will run.
As stated earlier, a large inverter is required and battery bank are needed to run appliances on solar power. You can cut down on the cost by using a portable 700-800 watt microwave. A 400ah battery bank should be enough to run most RV appliances with plenty to spare.
Can I Use Solar Panels to Run a Microwave?
Almost any appliance can run on solar panels, and microwaves are no exception. Running a microwave may require just a few hundred watts, but starting it demands a lot more.
A 1500 watt microwave needs at least five 300 watt solar panels to start up. If you run a microwave at max settings for 10 to 15 minutes it will use 400 to 500 watts. Longer heating / cooking times require more power. Compact microwaves use less power. You can probably get by with a 600W solar system under clear skies.
Just like with batteries, once the microwave starts, its power use drops and the solar panel can be used to run other appliances. You cannot connect a microwave directly to a solar panel. Solar power is DC and microwaves run on AC power. You need an inverter to turn DC into AC. From there you can run the microwave from the solar panels or batteries.
You do not have to choose between batteries and solar panels. You can use either one during the day, though at night you can only use the battery. Remember that your system also needs a charge controller to manage the batteries.
Running a microwave on solar power is possible, but it does require a decent sized system. The good news is there are portable versions available so you can save on power. This gives you more flexibility when deciding what microwave to run.
I am an advocate of solar power. Through portablesolarexpert.com I want to share with all of you what I have learned and cotinue to learn about renewable energy.