Instantaneous water heaters are becoming very popular, especially in smaller flats that only have a shower in the bathroom. They are very versatile and effective if you have the available amperage required to power them.

However, we do receive a lot of questions from customers, asking which would be more cost efficient, an instantaneous water heater or a small storage type water heater?

If you aren’t familiar with instantaneous water heaters, they are water heaters that have no tank, and heat the water up almost instantly. They need to be installed close to the appliance being supplied, and their flow rates tend to be weaker compared to standard storage water eddzipcexuheaters.

As an example, I’ll compare a 10L storage type water heater with a CEX-U, probably our most popular instantaneous water heater. I will be basing the comparison on the average price at the time of writing for a Kw/H.

Firstly, the CEX-U has a flow rate of 2.4 L/m at 38 degrees whilst set at 6.6kW. In order to get 15L out of this we would need to run it for 6minutes and 15 seconds (roughly!). With the average cost at the time of writing this blog being 13p per Kw/H, the cost to provide 15L of hot water from the instantaneous unit would be 8.9 pence. With instantaneous, the water is not stored, meaning there is nothing to be heated whilst the unit is not being used. With instantaneous water heating, you only pay for what you use, so is this cheaper than a standard under/over sink unit?

A 10L water heater heats up the water that is stored when it isn’t at the correct temperature. To compare the 2 products, I’ll have to compare the overall rate that the water heater can recover after being completely exhausted. We know that it takes roughly 12 minutes for a 10L water heater to recover completely. (We worked this out in a previous blog which can be read here!)
If you’re wondering why we’re comparing 15L of instant hot water to 10L of hot water from a small tank, it’s fairly simple. The water in the tank would be around 60 degrees C, and the instantaneous water would be 38 degrees C. In order to compare effectively, we need to mix some cold water with the hot from the storage type water heater to bring the temperature down to match with the instantaneous, which would be around 5L of cold.

Overall, the storage type heater works out to be cheaper, costing 7.8p to recover 10L of hot water. However, this would change dramatically on a larger storage type water heater. Anything over 10L and you would start to see the price for the instantaneous water heater better the storage type heaters price every time.

If you want to read more on instantaneous water heaters, click here. Or click the chat box in the bottom right of the screen to speak with us online!