How much beer can I brew, the question on all our minds. For the purposes of this article we’ll ignore the restrictions of floor area, fermenter size, bottling and storage and focus on the power (energy) and time factors around sizing your brewing vessels.
One consideration is the power of element you can facilitate and that depends on the current (amps) rating of the supply to your brew room, if we assume a batch size of 30L (8 USG). We can calculate the time taken to move a body of water from ambient to the boil. The figures below do not include the step times for mashing, To all the times below you must add the time to mash, the time to boil, time to cool, this can easily be another 2.5+ hours.
30L (8 USG), using a 2.7kW (about 12 Amps) element it will take 1 hour to heat the water/wort from 20C (68F) to 100C (212F). Total brew time 3.5+ hours. Plus cooling, transfer to fermenter, cleaning.
30L (16 USG), using a 5.4kW (about 24 Amps) element it will take 1/2 hour to heat the water/wort from 20C (68F) to 100C (212F). Total brew time 3+ hours. Plus cooling, transfer to fermenter, cleaning.
Double the volume, double the time. Double the heater power, with the same volume, halve the time. The above figure assume about 10% heat loss. If we consider 60L (16 USG).
60L (16 USG), using a 2.7kW (about 12 Amps) element it will take 2 hours to heat the water/wort from 20C (68F) to 100C (212F). Total brew time 5+ hours. Plus cooling, transfer to fermenter, cleaning. A 2.7kW element will struggle to keep pace with the heat loss from the system.
60L (16 USG), using a 5.4kW (about 24 Amps) element it will take 1 hour to heat the water/wort from 20C (68F) to 100C (212F). Total brew time 3.5+ hours. Plus cooling, transfer to fermenter, cleaning.
If we consider 90L (24 USG).
90L (24 USG), using a 5.4kW (about 24 Amps) element it will take 1.5 hours to heat the water/wort from 20C (68F) to 100C (212F). Total brew time 4+ hours.
If you want to brew 30L on a 13 Amp (3kW) supply, the total brew day will be a 3.5+ hours, plus cooling plus clean-up. Likely 5-6 hours start to finish.
Another way to decide is to first choose your preferred batch size and then using the rule of ~75 Watts per litre (~284 W per USG), decide the element power needed. Many systems have element sizes of between 50W – 100W per Litre (190W - 380W per USG).
A 30L (8 USG) system would have 2.25kW element.
A 60L (16 USG) system would have 4.5kW element.
A 90L (24 USG) system would have 6.75kW element.
A 120L (32 USG) system would have 9kW element.
Just ensure you have the electrical supply capacity to deliver enough current to the above element sizes, we would recommend leaving a ~15% headroom above the nominal element current before hitting supply capacity, this is to allow for normal supply voltage variations. So if you need 20A, make sure the circuit is rated for at least 23 Amp (115% of 20A). ***It is important to consult a locally qualified electrical professional. ***