How much hot water will I or my household/ business use each day?
Kitchen tap uses about 9 litres per minute.
Shower tap uses about 6 litres of hot water per minute.
Hand Basin tap uses about 6 litres per minute.
Washing Machine uses about 9 litres per minute.
Dishwasher should not be connected to the hot water pipe. You can void your warranty.
How to Calculate
How many minutes do you use each of the taps above? How much of this is used with in the same hour period? Divide this by the hot water systems recovery period. (Only Gas and Electric Hot Water Systems on a always on electrical tariff have a our recovery rate. Off Peak systems do not have a recovery rate)
When asking the above questions the first thing to keep in mind is that all hot water heaters have different energy sources. Some are electrical and some are gas. Some electrical hot water systems have the electricity on all the time and some do not.
Some electrical systems are set to turn on at low energy consumption periods of the day and night. This energy source is referred to as a “off peak tariff”. You can check on your electrical bill or call your Energy Retailer to find out what tariff you are on and what the times are when the power turns on. These times can vary slightly during the day. This can be altered or changed to a different Tariff. If you are interested in this type of system then adding up the amount of hot water you will use between these periods of when the power is not reheating your hot water will allow you to come closer to choosing the right size in liitres of stored electric hot water you require.
Electric hot water systems that have the power on all the time can be smaller as they reheat the water as soon as the temperature drops below the set limit on the system. This allows a smaller unit out perform a larger system that only heats at certain times. Systems that have constant power also use power at a more expensive electrical rate. But convenience may be more important then having a very large hot water system that may not fit into the allocated area. These smaller unit come with options of having multiple heating element or energy supplies for rapid re-heating.
Gas storage hot water heaters have a constant energy source that costs the same no matter what time it reheats. They recover very quickly. In many cases within 30 mins. So a smaller system lets say about a 80 litre storage system can be ideal for a house with just a shower or a small business just using a sink each hour. Using the bath is a different story as the tank only holds so many litres of hot water. A average size bath can be serviced by a 80 litre hot water tank but comfortably by a 135 litre tank. Units like the Rheem Stellar 330 which is a 135 litre system produces a massive 330 litres in the first hour and 180 litres each hour thereafter. So a smallish looking system can produce plenty of hot water.
Continuous Flow systems are only limited in the hot water they produce by the litres of hot water they can heat up or produce each MINUTE. They will continue to supply hot water all day if need be. Based on the limitations on these systems per minute supply, it will be unwise to use these systems if you have lots of hot water required at any one time unless you were going to connect multiple continuous flow units together which will in turn create the ultimate hot water system. Example, putting one Continuousflow system in will allow you say 26 litres a minute. Connect one other next to this and you literally double that per minute output. The more you join together the greater the capacity.