What would boil quicker/cheaper

[Libigage]

I have a 36 litre pot 36cm diameter so what would heat the water/wort quicker/cheaper a 3000kw induction hob 40x40cm unit plate approximately 28cm diameter or a 7.5kw propane/butane hob

 

[crowcrow]

Rule of thumb for piped gas is that gas is about 1/3 the price of electricity to generate the same units of heat. If this is from bottled gas it will depend entirely on the cost of the gas.

The induction hob has the benefits of heating only the bottom of the pan, whereas the gas heats the air etc.

In short... I don't know

 

[Thatscold]

3kW vs. 7.5kW.

I'm voting 7.5. Even with loses the gas has over twice the energy.

 

[Covrich]

I used to use a 7.5kw propane burner and now I use elecy.

Not doing any vigurous maths here but the propane was a fair bit more expensive.

I would say my elecy heats it up a lot quicker bt to be fair thats probably an indoor vs outdoor thing

 

[Libigage]

I used to use a 7.5kw propane burner and now I use elecy.

Not doing any vigurous maths here but the propane was a fair bit more expensive.

I would say my elecy heats it up a lot quicker bt to be fair thats probably an indoor vs outdoor thing

What electric heating are you using, I don't mind fitting an element if need be

 

[Covrich]

What electric heating are you using, I don't mind fitting an element if need be

To be honest I am using an all in one so thats a 2500watt heater (which I can adjust obv) plugged into my wall socket

 

[Drunkula]

Induction will be 90% efficient, gas is about 40% efficient. Propane is going to cost a fortune compared to electricity.
I've also got my boiler and mash tun mega insulated with foam and stuffing from a setee. I couldn't do that with gas. I had a go but the fire and toxic smoke made me give up after the third try.

 

[Bill_g]

I use a 7.5kW propane burner as I am cast out onto the patio by my better half who cannot stand the smell. Also the consequences of a major wort spill in my wife's pride & joy kitchen would not be survivable with all parts still attached!

I had in mind that I use about 1kg of gas for a typical heat up to boil and 60 minute vigorous boil. I don't have any notes of the calculation but I think that's about right, next brew I will check properly. This fits the maths roughly:
LPG energy density is 49MJ/kg. A 7.5kW burner will consume around 0.55kg per hour from these figures. So allowing for heat up time etc this fits roughly with the estimate of 1kg per brew. The cost of 1kg of propane based on a 19kg refill from my local Calor Gas centre is £2.85. For a 35 minute warm up followed by 60 minute boil the calculations indicate 0.87kg and a price of £2.48.
Calculations for a 3kW electrical input: Assuming wort is collected at +60C (allowing for losses) and assuming 30 litres then 3kW input will raise this to 100C in 28 minutes assuming no losses, so at a guess allowing 25% lets say 35 minutes followed by a 60 minute boil at full power. The total usage would be 4.75kWh. Googling an average price per kWh give 16.3p so a total price of £0.78
Obviously very back of envelope stuff, but calculations fit what I'd expect and point towards a gas heat efficiency of about 50% (i.e. gas & electric heater giving roughly similar heat energy per second into the liquid). My suspicion would be that this is a little pessimistic on gas and optimistic on electricity. But say assume gas would be at least 2.5x the price of electricity then that gives a decent working assumption.

I guess the other thing to check is whether your container actually work well on the induction hobb. We have one and some vessels do not work very well. Good quality stainless steel will not work at all. Most pans intended for induction hobbs include a layer of netall which is good at generating heat when eddy currents are induced in it.

But overall LPG does look expensive & next brew I'll collect some accurate measurements. However gas is convenient as it delivers a good reliable heat and removes the need to clean any heater elements, but the apparent difference does make me think whether I should be looking for a good immersible 3kW heater. I don't know if such things are available, I would not want to cut holes in my 50 litre kettle to fit one permanently.

 

[An Ankoù]

I use a propane burner outside to do the boil and I heat the mash and sparge water by electricity or on the kitchen gas stove. Purely for convenience. I can get at least 12 brews out of a bottle of propane- possibly more. I too have a 36 cm diameter pot it's so easy to measure the volume when sparging as each centimeter of height represents a litre of liquid.

 

[Drunkula]

I check the smart meter when I'm brewing. Last brew day a few days ago with no assist from the solar panels cost spot on a quid for a 23 litre batch using induction and my peculiar setup. When the solar's been raging I've had the brew day cost as little as 30p.