11/10/2022

A lid for every pot

The government suggests using a lid when cooking to save energy - but does it really pay off?

Gas and energy prices soared due to the war in Ukraine. To preserve our reserves, the Austrian government suggested actions to reduce consumption. These are often targeting private households. Reactions to these suggestions in social media were, as it often is the case, filled with ridicule and cynicism. One suggestion in particular evoked a lot of emotion: While cooking, you should be using a lid for your pot. This will reduce the energy needed to heat the contents.

A reason for the intense reactions on the internet seems to be the banality of these tips. How much energy/gas could you possibly save by such a primitive action? That is the question we will try to answer. The fact that cooking with a lid on your port is more energy efficient than without seems obvious. The question remains, whether the difference is significant, or a mere drop in the ocean. According to Verbund (Austrian energy provider) 1.5 liters of water can be heated three times as quickly just by using a lid. Since we enjoy performing calculations around energy efficiency, we want to quantify the potential savings with the help of a few experiments. 

Experiments - General Conditions

One of my 6-year-old daughter's favorite dishes is pasta bolognese. If you were to ask her directly, she might not say so, but judging by how often she requests it, there can be no doubt. One serving for our whole family requires 500g pasta (Pappardelle or Tagliatelle preferably) to be cooked. According to the instructions on the box, 5 liters of water are to be used for that amount. Realistically, we only use around 3 liters, which is also the amount I will use as basis for our experiments. First we’ll use a pot without a lid, then a pot with lid, and additionally we will try using an electric kettle. Since I know the energy consumption of my appliances, I can measure the time required for the water to reach a target temperature, and use that to calculate the cost difference. The water will be heated from 18° C (as it comes out of the tap) to 95° C (temperature measured right after the electric kettle signaled it was done). The stove used is an induction stove by AEG (Model HK764403XB Type 58GDD D4 AU). Its manual states a consumption of 3200 W for the highest level, which is the one we will be using. The electric kettle is a Braun Model 3217 / WK210, consumption according to its manual is 2280 W. It can only heat one liter at a time though. For calculating the cost in Euro, a price of 43 Euro-cent per kWh (from 31.10.2022) is assumed. 

For the scenario “electric kettle”, the stove would have to be used additionally to keep the first liters at temperature while the second and third liter is being heated. That would bump the consumption and the cost above the scenario without lid. Since it is also the most inconvenient and longest variant, it is unlikely to be adopted by many people. Therefore, I will save myself the effort of calculating the cost exactly.

Conclusion - Savings

In my setup, the lid saves my 0.6 cent per meal. Roughly one third of Austrians say they cook daily. If I were as commendable, that would amount to €2.16 per year (assuming one cooked meal per day, price per kWh 43 cent as before).

That is a saving of 5.11 kWh per year. If these numbers are similar for every one of the 4 019 700 private households in Austria, and each of these households cooks daily, we could save 20.5 GWh by putting lids on our pots. According to energie.gv.at, the total energy consumption in Austria in 2021 was 64.2 TWh. 

Therefore, roughly 0.03% of the total consumption could be saved. Considering not every household cooks as often, and the lid is not applicable for every meal (frying in a pan, baking in the oven), this number is very optimistic.

Conclusion - Energy/Gas-crisis

What does that mean? For us, it means we will continue focusing our efforts on helping the industry to become more efficient.

Further Reading
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