Inverter size for microwave?

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Straightman21

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Bearing in mind that the variety of convenience foods available specifically for microwaving is extensive, convenient and takes only a few minutes to cook, it would seem sensible to install one aboard. I have a small 240 volt microwave at home that states on the back that the input wattage is 1200 and the output 700. I would be grateful for advice as to the size of inverter I would need to run it for short periods please.
 
I have an 800 watt microwave on the boat. I recently fitted a 2000W pure sine wave inverter, and it runs the microwave perfectly. I'd suggest that RichardS's suggestion of a 1200W inverter would be possibly underpowered.
 
I started with modified sine wave that wouldnt start the MW, i now have a 1200 pure sine wave. Your battery bank will need to be big enough, its now mainly used in hbr, on shore power, rarely at anchor
 
Look on the back of the microwave and it will show the input power .

This is something like twice the cooking power.

So pvb's 800 watt will need at last 1600 watt power input the you have the inefficiency to add on so his 2000w inverter is about right.

I have a 2400 watt inverter modified sine wave and it drives our microwave which i think is 1200 watt
 
Straightman21 said:
Bearing in mind that the variety of convenience foods available specifically for microwaving is extensive, convenient and takes only a few minutes to cook, it would seem sensible to install one aboard. I have a small 240 volt microwave at home that states on the back that the input wattage is 1200 and the output 700. I would be grateful for advice as to the size of inverter I would need to run it for short periods please.
Click to expand...
Is Chicken Ping your favourite meal?
 
I'd say 1.2kW sounds a bit low as well, more like 1.6-2kW with little to spare.

No idea about your battery bank size but you will be drawing around 100A when running the inverter. However, that's only about 8Ah per 5 minutes use. That doesn't sound too bad until you realise that a 100Ah battery won't deliver anything like the rated capacity with a 100A draw.

No idea what your actual figures will be but could guess you will take about 6%-7% of available capacity from a 200Ah bank (assuming lead acid). Manageable but worth thinking about running the engine when using a microwave.

One other point worth mentioning. I use a Honda 20Eui to run a microwave using about 1200W and the output is claimed to be very close to sine wave. It has a very good reputation as a reliable generator which uses an inverter for approx. 1.6kW continuous output.

My wife has to use much longer times with the generator than with shore power. I can't remember the factor she uses but it is significant, might be around 25% longer cooking time.
 
A Victron compact Pheonix 1200w will run it, cheap and nasty inverters might not (include Sterling inverters in the nasty group).

Some microwaves will only run on pure sine wave.

Batteries need to be considered, 1200w at 240v will draw around 120a from the batteries. OK for heating something up, but you wouldn't want it on for too long with a small battery bank.
 
I have a Sharp 800 Watt microwave fitted, it's a cheap one, it replaced a built-in one so I had a very limited choice because I didn't want to alter the wood work.
It's a non inverter version, to run at less that full power it switches on and off. I'd have preferred an inverter driven one.
That works OK on a MasterVolt 2kW inverter, and draws about 150amps from a 500amp hour domestic battery bank. That's about 1.8kW.
I runs OK at full power from a 5KVA diesel generator, but the generator really doesn't like it switching on and off at a reduced power .
It's a great bit of kit, I used it every day, it saves gas, which is a pain to get refilled, and usually involves walking miles to a garage.
 
Great thread as was looking at microwaves and inverters last night on ebay..
some come bundled together but they seem to jack up the price too..
 
Straightman21 said:
Bearing in mind that the variety of convenience foods available specifically for microwaving is extensive, convenient and takes only a few minutes to cook, it would seem sensible to install one aboard. I have a small 240 volt microwave at home that states on the back that the input wattage is 1200 and the output 700. I would be grateful for advice as to the size of inverter I would need to run it for short periods please.
Click to expand...

I have a cheapo 2000w pure sine wave.
Mounted right next to the batteries.
I only run it with the engine on.
It feeds a 240v relay which switches power to 1 galley socket and the microwave.
Means I can have the microwave on OR boil a kettle.
It works well.
I have no gas BTW.
 
Elessar said:
I have a cheapo 2000w pure sine wave.
Mounted right next to the batteries.
I only run it with the engine on.
It feeds a 240v relay which switches power to 1 galley socket and the microwave.
Means I can have the microwave on OR boil a kettle.
It works well.
I have no gas BTW.
Click to expand...
What amps is your alternator , what is your battery bank ?
 
cherod said:
What amps is your alternator , what is your battery bank ?
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Battery bank is 2x 180Ah truck batteries. Huge things 1000CCA each.
Dont know alternator size. I had an upgraded one fitted for the domestic bank and it’s a big engine by yacht standards (6litre) so big. Even so I doubt it will keep up with the inverter draw but will help.
 
Elessar said:
Battery bank is 2x 180Ah truck batteries. Huge things 1000CCA each.
Dont know alternator size. I had an upgraded one fitted for the domestic bank and it’s a big engine by yacht standards (6litre) so big. Even so I doubt it will keep up with the inverter draw but will help.
Click to expand...
T y
 
Why on earth would anyone want to do this via an inverter?
If in harbour on shore power you have access to unlimited ---shore power!
If your boat is so big and power hungry you feel the need for a microwave afloat wouldn't you have a generator anyway?
If not surely the most cost-effective way would be to add a cheap 240v alternator? That way you don't have to murder your necessarily huge (and hugely costly) battery bank.
 
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