question

I have a Multiplus 5000, two now but in this context it isn't important, and have used induction hobs and a microwave for years.

My original hobs, cheap/simple, were 1.8kW each and the 5000, circa 4kW depending on PF was fine with them.

My newer hobs , Duxtop, are 2.2kW and although they are even better, PF wise, than the older ones that is pushing a 5000 much harder than you would want to.

IMHO a good quality hob at 2.2kW max on a 3kW inverter should be fine, although I personally would be looking carefully at the amps drawn when I first connected it.

Way more important is that even the best hobs I have found, including the ones I use, don't technically have variable power, at least not like a dimmer or speed control.

Cheap ones have one power and vary the on to off time ratio in pulses, typically in multiple second bursts. Better ones still do the same but do it in shorter pulses and may also have a lower power setting to avoid very low duty cycles.

My hobs will run at about 2.14kW if set to 10/10. reducing that drops there duty cycle until you get to 3/10 at which point the power of the pulses drops to about 960W and the duty cycle go's back up.

When increasing power the point at which the high power plus is used again is higher than 3/10 but I cant remember where, exactly.

This is almost certainly due to the induction circuit having to be tuned at a couple of values when oscillating and therefore incapable of true variable power. BTW Microwaves are the same.

When thinking about inverter loads it is worth noting that although a momentary overload will be tolerated, even if it is significant, repeatedly applying one with a pulsing load is going to break something, probably quickly.

I AM IN NO WAY SUGGESTING YOU TRY THIS but I suspect putting two 2kW induction hobs on a 3kW inverter would work if both hobs were on a low setting but every once in a while, when the pulses lined up you would be hitting the system with well over 4kW, there is a short start inrush for every pulse on cheap hobs.

The high current pulses will likely be short enough not to trip the system, but regular enough to do it serious damage within a fairly short period.

I now have two 5000's in series because my better half cant add 2+2+2 and come to the answer too much! apparently because one or more of those 2's was on low !!

She once complained that both hobs, all be it with on on simmer, and the microwave, tripped our power. There were also a load of lights on but I think it was the mixer or perhaps one of the fridges starting up that pushed it over the edge... Dont go there, I never planned to.

I love Victron kit but I wouldn't expect it to put up with that sort of abuse for long...

An additional battery and second inverter was less haste, in my case, that trying to explain the problem for the nth time.

My point is...

Don't fall into the trap of thinking linear when thinking about heating loads. Given the way Victron kit is built I do not 'think' inrush for a couple of cycles would be a problem but I am convinced that serially overloading a device for short periods, when it isn't looking at average load as far as I am aware, is a very bad idea.

That said, induction hobs and microwaves are great IMHO, all our cooking is solar during the summer.

last points, I have 2 single hobs 2.2kW each. A dual hob will almost always be a large, ish, 'ring' and a small 'ring' in a single package, in the UK, to make the appliance, as a whole, compatible with a 13A plug.

Anything with a simmer stat or thermostat, so old style heating plates, and even halogen hobs, will be almost unity PF because thy are resistive. These are as kind as you can be to in inverter.
We use on old style 1.2kw single boiling plate to heat a giant, 20 odd litres, but insulated, pressure cooker when canning.

Hope this is food for thought.

Al