The appropriate size of inverter (watts) to power a microwave oven depends on the inverter’s cooking power and ultimately its input power consumption.
Here is an indicative guide of suitable inverter sizes (W) to use with ovens of different sizes (cu.ft) and their corresponding cooking power.
Indicative inverter sizes for various microwave oven sizes (cu.ft)
| No | Microwave oven size (cu.ft) | Indicative cooking power (W) | Indicative corresponding input power (W) | Inverter size (W) |
| 1 | 0.7 | 700 | 1,050 | 1,200 |
| 2 | 1.1 | 900 | 1,550 | 1,800 |
| 3 | 1.2 | 1,200 | 1,480 | 1,800 |
Note: The inverter sizes are selected based on commonly available standard inverter sizes and to accommodate the microwave’s momentary surge power draw.
Why you should use a pure sine wave inverter for your microwave oven?
It is generally recommended to use a pure sinewave inverters to power a microwave oven to minimize the risk of damage to the microwave.
Some users reported their microwave ovens not working, noisy or running hotter than usual when connected to a modified sine wave inverter.
Based on this, it is best to stick to powering a microwave oven with a pure sine wave inverter.
Tips to size an inverter to power a microwave oven
# 1. Size the inverter based on the microwave input power consumption and not its cooking power
Whereas the microwave ovens are sold and packaged according to their cooking power (watts), when sizing the inverter, use their input power consumption.
The input power consumption is usually slightly higher than its cooking power (W) to compensate for internal conversion losses in the oven.
Note: Larger microwaves (cu.ft) have higher cooking power (watts) and tend to have higher input power consumption (W). If you have a limited power supply, consider using a smaller microwave oven (cu.ft).
Smaller microwave ovens under 1 cu.ft for example have a cooking power in the range 700-900W and a much lower power draw.
In addition to properly sizing the inverter, get the ***right size of wire*** and ***battery bank*** for your microwave to work properly.
# 2. Select a suitable wire gauge for the oven’s inverter battery cables
Microwave ovens can draw large amounts of current from the battery. As an example, a 1,000W microwave draws about 1000/12 = 83A from a 12V battery!
If the battery cable sizes are not sized properly, the large current draw will result in a large voltage drop which may stop the microwave from working or cause a fire.
Here is a guide for wire gauges to use with various inverter sizes (source: Samlex power recommended sizing of DC Input Wires)
| No | Inverter rating (Watts/volts) | Wire gauge (AWG) | Voltage drop (%) |
| 1 | 1500/12 | #2 | 1.6% |
| 2 | 1500/24 | #4 | 0.6% |
| 3 | 2000/12 | #2/0 | 1% |
| 4 | 200/24 | #4 | 0.6% |
Note: This assumes that the wire lengths are 3ft long. Always try to mount the inverter close to the battery bank to minimize cable length and voltage drop.
In addition to properly sizing the battery wires, the battery bank needs to be sized properly.
# 3. Size the inverter battery bank to maximize battery life and use of oven
Microwaves can significantly draw down your battery bank if used for long periods. You need to invest in a reasonably sized battery bank to avoid running your batteries flat.
To appropriately size the battery bank for a microwave to run, you need to first establish:
- the inverter’s input power consumption (watts) – for this, check the inverter’s back plate
- Estimated operating time of the inverter
You can then use the formula below or the calculator to work out the microwave’s battery bank size.
But what if you, you choose not to use an inverter as a source of power for your microwave, what other choices do you have?
Alternatives to using an inverter to power a microwave
To avoid the costs associated with investing in a battery bank, you may consider using :
- a generator to power the microwave inverter
- bottled gas for cooking
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