Fresh wort 'kits' from MM

[JamesF]

Still under £10 a brew just. But that didn't include leccy. Next brew gets the energy meter plugged in, but I doubt that will exceed £1

That would be interesting. I'd do mine, but the sockets are awkward to get to once I have hot wort splashing about. My gut feeling is that for a five gallon brew length it could easily be more than £1 though:

Let's say that during the course of the beer-making session you have to heat thirty litres of water from 10°C to 100°C. For some bizarre reason one of the things that I remember from schoolboy physics is that it takes 4.2J of energy to heat 1cc of water by 1°C. So heating 30 litres by 90°C takes 11,340,000J or 11.34MJ. 1kWh = 3.6MJ, so that's 3.15kWh. It's not just the heating though. There's the 90 minute(?) boil, during which time energy is being put into the wort and lost through the boiler walls or in the phase change of water to steam which is then also lost to the environment. I have no idea how much that will be, but I suspect that unless you're paying a fair bit less than 25p/kWh you wouldn't see change from £1.

Please do post your results if you try it though.

James

[MashBag]

I will but you might be in for a surprise

[JonB]

Still under £10 a brew just. But that didn't include leccy. Next brew gets the energy meter plugged in, but I doubt that will exceed £1

Let's say that during the course of the beer-making session you have to heat thirty litres of water from 10°C to 100°C. For some bizarre reason one of the things that I remember from schoolboy physics is that it takes 4.2J of energy to heat 1cc of water by 1°C. So heating 30 litres by 90°C takes 11,340,000J or 11.34MJ. 1kWh = 3.6MJ, so that's 3.15kWh. It's not just the heating though. There's the 90 minute(?) boil, during which time energy is being put into the wort and lost through the boiler walls or in the phase change of water to steam which is then also lost to the environment. I have no idea how much that will be, but I suspect that unless you're paying a fair bit less than 25p/kWh you wouldn't see change from £1.

Please do post your results if you try it though.

James

I think you've over-complicated that a bit, and this method also does not take into account ineficciencies and losses within the system. Not all the energy drawn from the wall will go into the beer, and you will be loosing energy to the surroundings that has to be replenished.

A far more efficient method is to just take the element draw (in my case 2.4kw) and multiply this by the time (in hours) it is running. Granted it may not be drawing the full 2.4kw all the time, but it means the calculation is conservative.

For me, assuming a 23L final volume:

• Heating mash water to ~70-75 degrees takes ~30 mins

• Heating sparge water takes ~50 mins*

• Raising sparged wort to boil takes ~20 mins

• Typical boil length for me is 30 mins

*this uses an older s***y Brupaks kettle as the digiboil doesn't fit above my mash tun and collecting vessel due to ceiling height, 2.4kw)


Total heating time: ~2hrs 10 mins (2.166 hr)
Total Energy: 5.2kwh (2.166hr x 2.4kw)
Current Energy price cap up to 30/09/23 per Kwh = £0.3011p

Total Brewday energy cost = £1.57 for 23L

(this doesn't include the cost of gas used to heat the water out the tap for cleaning, etc. but given our summer gas usage when the heating isn't on is about £15/month I'm going to assume a brewday cost is 4/5ths of FA).

In all fairness I expected this to be a lot higher. My typical ingredient cost is probably about £20-£30.00 per batch (~6kg of grain @ ~£2.20 and 1-2 of 100g bags of hops @ ~£6.00ea, not taking leftovers into account)

This means my cost per batch is circa ~£22-35.00 per 23L (£0.55-£0.88/pint). Having said that I have some outlier recipes that use a LOT of hops which I suspect are closer to £1.50/pint...

[JamesF]

Yes, I was just looking at the absolute minimum possible amount of energy required to heat up the water from the tap until it boils. All things being equal, it's just not possible to get 30 litres of water from an estimated "tap temperature" of 10°C to 100°C without putting 3.15kWh of energy into it. At your price that's about 95p. Clearly there will be all sorts of losses increasing the cost as we've both said. That's why I suspect the total will have to come out at over £1 unless there are other things going on (you could pre-heat the water using solar or something, for example, or brew at night using cheap rate electricity, or for the really hardcore, pre-heat the water for one batch by using it to chill the previous batch).

But I agree, it looks likely to be quite a small figure relative to the cost of the ingredients which is quite a relief to me. I'd have been quite distressed if it had turned out that the cost of the electricity used was a large proportion of the ingredient cost. I think for my own interest I'll look at the next recipe we plan to make and see if there's some way I can practically put power meters on the plugs to be able to get a more accurate idea of total cost, but if we said it was of the order of 70p/pint then I won't be crying into my beer

James

[JonB]

Fair enough, I have to admit I was quite concerned by what that total figure could be. You can normally spot my brewdays on the smart meter usage graph...(I suspect that's because we don't use a lot, so an extra ~£2.00 worth of electric one day stands out a bit).

At least we know the biggest problem is the price of Grains/Hops rather than gas & electric.

Even so the cost of a pint isn't that high (if you ignore the time sunk into it...). It's interesting that those fresh wort kits work out at £2.50/l (~£1.30/pint) Vs £0.88 for mine.

Would seriously consider though if I didn't have the time to brew properly....

[MashBag]

I am going to meter this, because there is a huge amount of unknowns.

Brewing overnight the pump runs longer.
The kettle does have insulation (lots)
Short boil, but an 85c/min hopststand.
I will then ferment in the kettle for 8-10 days.
I have a renewables so the weather might affect it.
Do we include the extractor fan?

I will be brewing in about a month, unfortunately for this experiment I have just stocked up.

[markl]

I've had this account for ages but somehow never get round to posting, hello everyone

In case it helps, I stuck my ancient Brennenstuhl PM230 in series with a Grainfather G30 back in May. It claimed I used 4.8kWh producing a 19l brew with a 60 min boil. No idea what the error might be on that number. Unfortunately I don't have two meters, so don't know how much my boiler used in getting the ~13l sparge water up to temperature, but JamesF's method will be close enough there.

So ~6kWh from cold to pitching. That's ~2 quid on my 33p (green) tariff, or ~5-6 pence per bottle.

Naturally more later on - both keeping the wort temperature stable and, importantly, making sure the saison was nice and cool to drink over the summer : )

TTFN

[Cobnut]

So probably £3-4 per 20-25L batch, or perhaps 10p/pint.