If we are talking non winter (when I'm on shore power - in town).
Using the cooktop or/and the microwave/toaster - comes down to taking a few things into consideration.
Time of day - are we talking about cooking 2 or 3 eggs and a couple of slices of toast --------- or
are we talking about a meal later in the day - and, that meal? - are we talking about something that's going to take 5 or 7 minutes in the pan - or something with bone in it like full chicken legs with the bone which takes a bloody age.
it also depends on - if it's morning and I'm going to move - in which case - I can hit it considerably harder because I'm going to get it back in a hurry with engine running even if it's cloudy.
Lets go a worst case for an example --
Battery full or near enough ----
afternoon - I want to do say 10 minutes on the induction -
******note this - 'almost all' cooking is done on the 400 watt setting -
this means that the cooktop runs at 2000 watts - but, only switches on for a couple of seconds then off for maybe 6 - then, on then off - etc etc.
but, for an afternoon with no sun - I do NOT like my batteries down much at all overnight - so ---------- I have two choices --
run on the genny - which means that - the batteries aren't involved at all - I just use mains ---
but, that means going forward and firing up the genny -
if it's pissing rain and blowing a gale ------- well, bugger that -
I 'could' if I chose - just run on inverter and wear the batteries being down 'a bit' overnight - but, I can also - switch on the main engine -
run the inverter - and, at 400 watts induction setting -
the batteries will be in POSITIVE about 1 amp an hour -
*** note that well -- it's important -
I'll restate - with the main running - I can run the induction and actually MAKE power -------------- only up to the 400 watt setting though - above that - go to 600 watts and you are depleting --------
ditto the microwave.
Oh -- btw --- I agonised in whether to change to Lithium batts or stay with LA - I chose to stay with LA - and, it's been a very wise decision - the system works fine - and, a LOT cheaper and easily replacable.
Some ideas on how it's been - I have now winterised and taken the genny off the front deck from it's little house and put it in the cockpit locker - it will come out again before I move into the canals for the cruising season.
In summer - I ran the genny - really only a few times - and, some of those times was to actually give it a run - it wasn't necessary.
There was the rare time where we had heavy cloud for a few days - if I ran (travelled) - it made no difference - if I was stopped - then, I might have only once actually ran the Victron charger to hurry things up.
Basically - summer is a doddle. - On a normal morning - eggs and toast the power is back by morning tea time.
I do -in summer use a little camping walking stove to make my coffee water - *** that's an important point - it's the only gas I have on the boat.
In winter for ALL cooking - I use electric.
When running - IF one wanted hot water - I have actually used the inverter to run the electric hot water - I let it run for about 10 minutes - give it a rest, then the batteries replenish - then, I give it another go for about 10 minutes and I have full hot water -
I've only done that a couple of times - because I really don't need hot water -
and, for the vast bulk of moving cruising -now, I use canal water or river water - either bathe in the creek -- or - shower in the cockpit - depends on temperature of the air if I add any hot water or not.
