Running a Microwave on 12V; what do you need?

There’s been a big shift towards running large 240V items when you’re away from a power source, and today we look at what’s actually needed to run microwave on 12V, and whether its really worth it.

There’s no doubting that having access to power makes life easy, and people have decided that its worth while taking that sort of power with them camping.

Is a microwave a necessary? Absolutely not. Can you live comfortably without it? Yes, no worries at all. Does it make life easier? Yep, it probably does. Should you get one? Well, that depends!

How do you run a microwave on 12V?

Actually, its really simple; you need a suitable battery system, and a suitable inverter. Beyond that, it gets a bit more complicated.

Sizing your inverter

If you want to run a 240V appliance, you need to get an inverter that is capable of doing it. Every single appliance that you purchase will have a sticker on it, that tells you its consumption.

Microwaves generally start off at about 600W, and work their way up from there. Induction cooktops are often up to 2000W, and that is the maximum power consumed.

Be aware that some appliances can use more power on start up, and you won’t get away with an inverter that is only just sized correctly.

Its good practice to get something with a bit of wiggle room anyway, and we ended up with a 3000W Renogy Inverter, even though we’ll probably never run anything more than 2400W.

However, before you go out and buy an inverter, make sure you consider the rest of the components needed, as this won’t be cheap, and you can’t necessarily just buy an inverter and be sorted.

What do you need to power the inverter?

Inverters need a lot of power, and you need a serious battery system to run them.

Most lead acid battery systems are not going to be suitable to run microwaves and induction cooktops in a portable, 12V application purely because the batteries aren’t able to discharge quick enough without doing damage. If you draw a lot of power from a lead acid battery in a short period, its probably going to fail.

So, onto the power draw side of things, and I want to start with a basic example of how much extra power these units might use. Your average 12V fridge (like an Engel, or Waeco, or even upright fridge) is going to use about 4 amps of power, or somewhere around 50 watts.

A microwave uses a minimum of about 60 amps, or 700 watts, and work their way up to around 1400W, or 112 amps. This is without considering some inverter losses, which whilst relatively minor in the scheme of things does make a big difference.

Please let those figures sink in for a minute; a microwave is going to use about 15 to 28 times the electricity of your 12V fridge, and that means you need a serious battery system to cope with the demand.

The actual size that you get should be determined by two things; the maximum discharge rate from your battery system, and how long you want to be able to run your batteries without charge.

Always make sure that your batteries are capable of handling the current draw before you commit to buying anything, and we generally advise having 3 days worth of power on board if you are reliant on it, and this is where things get interesting.

That is the total demand too, including anything you run (phones, laptops, lights, water pumps, fridges, freezers, other 240V appliances and so forth).

How are you going to charge the batteries back up?

The final piece of the puzzle is putting the power you’ve just used to cook back into the batteries. This is most commonly done by solar panels, or by a DCDC charger from the alternator power of your vehicle.

You can get AC chargers which are quite powerful, but if you are off grid then these are probably not any use anyway.

Most DCDC chargers are only good for about 60 amps (and alternators are often no good for much more than that anyway), so you have to drive for a full hour to put 60 amps back into your battery.

The good thing about microwaves is that you generally don’t use them for extended periods. If you used one for 15 minutes a day, at 1500W, its only going to have used 30 amps, which is half an hour driving, or easily within the reach of an average solar array over 6 hours.

Do you need a microwave? Nope. Are they handy? Maybe. We didn’t get one because of weight and space constraints, and we don’t really use one enough to justify it. We much prefer our induction cooktop!

Do you have a microwave? How often do you use it? How does your 12V system go running it?

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