Hi All, Have looked everywhere for the answer to this question regarding calculating Hot Water Cylinder power and time. I found this forum while trying to find the answer through Google. Maybe someone here can help. Im an electrician and would like to find out how much energy (kWh) is to be consumed to increase the water temperature up to a certain level. Say if you had a 300 litre cylinder, with a 3kW element, specific type of thermal insulation, and had to increase it from 30 degrees celcius to 60 degrees. Surely there must be a formula on calculating this value? As we know the volume of a Cylinder (in meter cubed) is = pi * diameter squared * height / 4...Then by including the losses (efficiency), element power rating, temperature increase required and maybe some other factors will give us the answer??? Theres also the time, how long would it take to heat the water to 60 degrees from 30 degrees? Thanks for your help, murphfan51 somebody 28-03-2009, 10:15 PM Welcome to Press F1. I know some manufacturers have a "recovery time" specification on their cylinders, which tells you how long it takes to heat a full tank of cold water up to a certain temperature (55 degrees I think). It might be worth finding a few of these figures, as it's likely to be quite an unexact science. robsonde 28-03-2009, 11:03 PM Hi All, Have looked everywhere for the answer to this question regarding calculating Hot Water