A few days back, I saw a post from someone who was beating up induction cooktops as being no good. He’d written that to boil water, it drained his 200aH lithium battery setup 28%. When I read it, I thought rubbish; that’s impossible, and I’ve done some testing since to look at the induction cooktop energy consumption on 12V.
For the record, 28% of 200aH would be around 56aH, which you’d probably be able to boil 10 litres of water with, so old mates maths, or shunt is way out.
We run a Westinghouse Portable Induction Cooktop, and are really happy with it. We also have a Victron Battery Monitor and Shunt that tells us exactly how much power is being used, and I did a number of tests when the solar wasn’t doing anything, to see where it would go.
To start with, here’s the power draw on different settings:
200W – 88 amps, cycling off most of the time
400W – 88 amps
600W – 88 amps
800W – 88 amps
1000W – 88 amps
1200W – 108 amps
1400W – 128 amps
1600W – 142 amps
1800W – 131 amps
2000W – 128 amps
If you are looking at the above figures and thinking that doesn’t look right at all, you aren’t alone. However, it is correct, and it relates to the cycle times. When its running at 200W it comes on for a split second at 88 amps, and then spends a good chunk of time off.
As you increase up to 1000W it cycles less, and from 1200W it starts to go up. I find it really strange that 1600W has the highest instantaneous current draw, but again, its due to the unit cycling on and off.
Despite the higher current draw at 1600W, the heat output would be less than at 2000W because its cycling on and off.
In actual fact, when it comes to boiling water this way its almost irrelevant what setting you have it on, as the heat loss is minimal and virtually all of the power you use is converted into heat. You can run it at 200W for 15 minutes, or 2000W for 1.5 minutes, and still consume a very similar amount of power.
If you’re into your cooking, you’ll know that this is one of the reasons why some people do not like induction cooktops. Despite being on the lowest setting of 200w, you’re getting roughly 68% of the maximum power for a split second, and then its cycled off for a number of seconds.
Now, onto boiling water. We normally boil water with our smallest square smartspace pot, which when about 2/3 full is enough for 4 hot drinks, and when almost completely full, is enough to warm water for the dishes (we just get it hot enough to touch, and use the whole lot). This avoids having to add cold water to get the water temperature just right.
To boil enough water for 4 hot drinks on 2000W, our shunt shows we consume 13.7Ah. That’s about 4% of our battery capacity (340aH) and is replenished in well under half an hour with decent sun.
Warming water for dishes (a full square smart saver pot to just hot enough that you can put your fingers in) – 10 aH, done at 2000W.
Cooking bacon and eggs for two – 12aH. Done at a mixture between 600 and 1200W.
Cooking pasta (including mince) for a family of 4 – 30aH. Done at 2000W for the water until boiling, and then backing it off to 600 or 800W, with the mince cooking done at 600 – 1000W.
Induction chews the power
There’s no doubt that using an induction cooking for camping absolutely kills the power, and if you are cooking something that needs a lot of heat, you will use a lot of power.
However, with a good solar setup its surprising how quickly the batteries replenish, and we prefer cooking on induction a million times over than using our little gas burner inbuilt in the Reconn R2!
We’ve got a gas vs induction cooktop post that goes into this in a lot more detail, but we’re happy using induction when we can.