Whilst waiting for the tide at Torksey Lock on Saturday afternoon we took a walk to Torksey Caravans, not with the intention of buying anything but it was a way of killing time.
Whilst there this low wattage stainless steel kettle took our fancy. The Morphy Richards one we had on the boat was starting to play up a bit and at 1100 watts, even though low wattage compared to a household kettle still took a fair old draw from the batteries, close to 100 amps when taking account of some inverter inefficiency. Not a massive problem with the engine running as the alternator supplied some of that power but the first cuppa of the morning without the engine running dragged the voltage down enough to set the low voltage alarm off on the inverter, albeit only usually for the last 30 seconds or so of the boil, it clearly wouldn't be doing the batteries any favours.
The new kettle is 650 watts, so quite a bit less powerful and allowing for inverter losses should draw in the region of 60 amps. With the engine running the new alternator will pretty much keep up with this, whereas with the old kettle the draw was still around 40 amps from the batteries even with the engine running.
It will of course take slightly longer to boil the water needed for a couple of mugs of coffee. With the engine running this really won't matter, for the first cuppa of the day with the engine switched off we hope that the reduced draw will not drag the voltage down quite so far even though the boil time will be slightly longer.
We didn't get time to try it out last weekend but hopefully will try it out this weekend and see if the theory rings true in practice.