Unsubsidized LPG vs Induction cooking

The good is that you realize that it is time to switch to electric alternatives for cooking food like induction cooking. Let's find out how reasonable it is to switch to an induction cooking from an LPG stove.

At the time of writing this blog, the subsidized 14 kg cylinder costs Rs 420 while unsubsidized ones cost Rs 900. On the other hand, subsidized household electricity costs Rs 5 per unit (kWh).

We will compute the useful heat energy per Rupee spent on the fuel in both the cases. First let's compute useful heat energy from a 14 kg LPG cylinder. The heat produced by 1 kg of a fuel is called Calorific Value. According to Wikipedia, 1 kg of LPG produced 46.1 MJ of heat. Hence, 14 kg would produce \(14 \times 46.1 = \) 645.4 MJ of heat. This is the amount of heat we get for Rs 420. Hence, we get \(\frac{645.4}{420} = \) 1.5367 MJ per Rupee of heat. However, a lot of heat is lost during transmission from burning LPG to actually cooking food. For an average LPG stove and cooking utensil the efficiency is known to be only 40% [Source]. Hence, in effect we get only \(0.4 \times 1.5367 = \) 0.61467 MJ per Rupee of heat. For those who love equations, heat per Rupee from LPG using average stove and utensils is given by
\[\begin{align}
H_\text{LPG} &= \frac{\eta C m }{ p} = 0.615 \text{ MJ/Re}\\
\text{where} & \\
\eta, \text{efficiency of heat transfer} &= 0.4 \\
C, \text{calorific Value of the fuel} &= 46.1 \text{ MJ/kg}\\
m, \text{mass of the available fuel} &= 14 \text{ kg} \\
p, \text{price of available fuel}&= \text{Rs } 420
\end{align}\]

The corresponding calculation for an induction stove is relatively simple. The efficiency of an induction stove is high because it directly heats up the utensil. According to Wikipedia, the efficiency is as high as 84%. By simple unit conversion we know that 1 unit of electricity is same as 3.6 MJ. In other words, we say that we get 3.6 MJ in Rs 5 or \(\frac{3.6}{5}=\) 0.72 MJ per Rupee. Though, effectively, we can use only \(0.84 \times 0.72=\) 0.6048 MJ per Rupee. In equations
\[\begin{align}
H_\text{induction cooking} &= \frac{\eta U }{ p} = 0.605 \text{ MJ/Re}\\
\text{where} & \\
\eta, \text{efficiency of heat transfer} &= 0.84 \\
U, \text{energy in one unit of electricity} &= 3.6 \text{ MJ}\\
p, \text{price of one unit of electricity}&= \text{Rs } 5
\end{align}\]

Here, we see that consumer cost efficiency of Induction Cooking (0.605 MJ/Re) is very close to standard LPG cooking under subsidy (0.614 MJ/Re). However, if we consider the cylinder cost to be Rs 900 (without subsidy), the heat per Rupee for LPG drops to 0.287 MJ/Re.

The conclusion is that if you are a household that uses more LPG cylinders than those are subsidized, it is better to use an Induction stove than unsubsidized LPG. However, with the current uncertainty with power supply in India you would have to depend on both LPG and induction cooking.

Edit:
Induction cooking needs special utensils and cannot be used for deep frying and roasting. Moreover, the power prices at some places like AP have increased by 30% making the subsidized LPG a lot more cost effective than induction cooking.

Having said that, another point in favour of induction cooking is that it depends on centralized power generation. Petroleum as we know is a limited resource that is predicted to be exhausted in a century. While we can generate electricity by various alternatives like nuclear power, hydroelectricity. Going by this intuition, the electricity prices won't rise as rapidly as the petroleum prices are going to. Hence, it is just a question of time when using electricity becomes cheaper than LPG.

On the other hand, there are other possibilities like natural gas pipelines that may last longer, may be cheaper and increase the longevity of gas stoves. Moreover, the conversion of heat to electricity and electricity to heat is not so efficient as seen at the consumer end.