How much power and energy does an induction cooktop use to cook chorizo and eggplant pasta?

Tim Eden wanted to know how much power and energy his new induction cooktop used so he undertook some simple experiments.

Since ditching my gas cooktop and electrifying my house last year I have grown to love induction cooking. There was an adjustment period coming from gas, but it was fairly brief and now I don’t miss gas cooking at all.

I love induction cooking because of its speed and responsiveness, the health and safety benefits of no longer burning fossil fuels inside the house, and the ease of cleaning up during and after cooking.

Another key benefit of induction cooktops is their energy efficiency. I was interested to find out exactly how much power and energy they actually consume while cooking so I decided to conduct some experiments.

I wanted a better understanding of how much power and energy the induction cooktop uses to make an evening meal because it will help me gauge my power and energy consumption in the future when I install a home battery. For anyone wanting to live off grid with solar and batteries, this may also help them size their systems appropriately.

Before installing my induction cooktop the electrician ran a new 32 A circuit into the kitchen. This turned out to be easier than expected. A 32 A circuit can supply just over 7 kW of power to the induction cooktop, but this doesn’t tell the whole story.

My Enphase solar system is equipped with consumption monitoring so I can see the overall power consumption for the house in real time.

I also wrote some of my own software to gather data from the solar system and store it in open source monitoring platforms using Prometheus and Grafana. This gives me more flexibility and makes it easier to analyse the data at a later stage.

Experiment 1: Chorizo and Eggplant Pasta a la Tim

To test how much power and energy it takes to cook a typical meal I made a simple chorizo and eggplant pasta using two of the four zones on my cooktop. This involved frying the chorizo first before combining it with the other vegetables and a tomato base. The sauce was left simmering in the background while the pasta cooked.

For the record, the end result was delicious.

The annotated graph below shows both power and energy consumption while cooking the meal.

Power consumption is shown on the left axis with the shaded areas and energy consumption on the right axis with the single blue line. Power consumption for the sauce and pasta are highlighted in different colours to make them easier to see.

Electricity consumed while cooking the pasta dish (Source: author)

300 - 400 W of power was being used elsewhere at the same time for the fridge, range hood exhaust fan, and kitchen lights.

However, the power consumption for the induction cooktop can still be isolated by subtracting this background consumption from the total consumption shown in the graph.

My induction cooktop has 9 power levels for each zone with an optional boost mode for additional power. The results showed that frying meat or vegetables using a single large induction zone required 1100 W on setting 7, or 1400 W on setting 8. Simmering the sauce on setting 4 used only 400 W.

Next up, boiling a large pot of water for the pasta on boost mode used 3500 W. Once the water was boiling, cooking the pasta used 2200 W on setting 9, before I turned it down to setting 8 and reduced the power to 1300 W.

I cooked the sauce and boiled the pasta at the same time.

In terms of energy consumption, the entire meal used 1.41 kWh of energy to cook. This equates to an electricity cost of 48 cents, assuming the average NSW electricity price of 34 c/kWh, or just 7 cents if consuming self generated solar with a feed-in-tariff of 5 c/kWh.

Experiment 2: Boiling water

After observing how much power boost mode used while cooking a meal, I wanted to see how different settings affected energy consumption.

For example, I wondered if boost mode wastes energy by being less efficient compared to lower settings given the cooktop has to work harder.

To verify this I took a medium sized pot and boiled 2.5 L of water on boost, then used setting 9, and setting 8. The pot was left to cool completely between each test and care was taken to position the pot in the exact same spot using the lines on the cooktop as a guide to rule out as many variables as possible.

Electricity consumption while boiling water using different settings.

I also measured energy consumption while boiling water in a standard electric kettle for comparison. I could only boil 1.25 L of water in the kettle so the time taken and energy consumption was doubled to make it equivalent to the induction cooktop tests.

The results of this experiment were interesting and are summarised in the table below.

For comparison, the amount of energy required to boil 2.5 L of water ends up being the same as the energy required to mow my lawn which I found interesting.

If I hurry, I can usually finish edging and mowing my lawn in about 1.5 hours with a single charge of a 5.0 Ah, 56 V battery in the battery powered garden tools.

280 Wh of energy is also enough to drive about 2 km in an efficient electric vehicle.

Conclusions

Boost mode on an induction stove consumes significantly more power than regular settings - a single large zone on boost can use up to 3.7 kW.

Even though the maximum power draw on different settings varies a lot, the amount of energy consumed to boil the same amount of water is similar. So if you are in a hurry, there is no harm using boost mode.

A single zone portable induction cooker is able to supply up to 2400 W from a standard 10 A powerpoint.

Assuming it has similar energy efficiency to a larger induction cooktop, it should be roughly equivalent to one zone of an induction cooktop using regular non-boost settings. In other words, it might take a bit longer to boil water, but for other cooking it should provide similar results to a larger cooktop.

Simmering sauces or making stock consumes very little energy. For example, simmering for an hour on low settings requires around 400 W and consumes only 0.4 kWh of electricity. This would cost 13.6 cents assuming the average NSW electricity price of 34 c/kWh, or just 2 cents if consuming self generated solar with a feed-in-tariff of 5 c/kWh.

Lastly, boiling water using an electric kettle is only 5-10 % more efficient than the induction cooktop, so it is not worth the energy saving of first boiling water in a kettle and transferring it to a pot.

I used to boil water in the kettle for pasta with the old gas cooktop because it was much faster that way but that is no longer necessary with fast induction cooking.

The results from my experiments also closely match this article, which found an induction cooktop is slightly more efficient than an electric kettle. The minor differences from what I observed can be explained by using different appliances as well as experimental error given I only ran each of my tests once.

Author
Tim Eden
EV & renewable energy enthusiast
May 26, 2024
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