actual price of a bath or shower for water and heating

[Christophe]

What is the actual price of a shower or bath depending on the water consumed?

Let's try to estimate the actual price of a shower (or a bath, only the amount of water changes) according to the following formula:

Price = price of water + price of water heating.

So the longer it gets, the hotter it is, the more it costs!

For simplicity, the losses in the pipes and the domestic hot water system are neglected. Whoever wants to take them into account will be able to increase the price of the heating of 20% approximately.

Those calculations bored can skip steps c) and concluding in red below.

a) Price of water consumed: about 0.4 € / shower

The price of water depends on the municipalities.
It is about € 3 / m3 in France
In our corner of Belgium it is 4 € / m3 (from a little less than 3 euros to 4 euros in 4 years without anyone really speaking ... short is not the debate)

A shower is said to consume about 50L.

Actual flow rates were measured here from various knobs: water-pumping-filtration / debit-reel-heads-de-shower-economic-in-water-t12498.html

Results: of 6 L / min for a shower to misting 18 L / min for a zenith (open valve thoroughly, actually the
valve is not necessarily fully open), so let's keep an average value of 10L / min

A quick shower 5 minutes open tap consumes much 50L or the 50L announced earlier.

A long shower, say 15 minutes open pommel, will therefore consume about 150L. We approach the capacity of a bathtub, so from a moment it is logically more interesting to take a bath than a shower!

In euros and Belgium, just for the price of water we have 50 / 1000 * 4 to 150 / 1000 * 4 = 0.2 to 0.6 euros!

b) Energy price of water heating for a shower: about 3 kWh (2 kWh if thrifty) is 0.3 euros 0.6 euros / shower (depending on price per kWh)

We make the thermal balance of the amount of water consumed noted X and we converted afterwards into euros ...

Energy = X * T * Delta Pc

Cp = 4.18 kJ / L
Delta T = varies according to the T ° of cold water on arrival in the housing and the T ° requested by the user.

Usually you take a shower between 35 and 40 ° C, from 45 ° C it begins to have a burning sensation.

Taken is the average value of 38 ° C.

Cold water arrives in the housing between 8 ° C and 13 ° C. This varies according to the year. 10 ° C is retained. The delta is therefore 38-10 = 28 ° C.

We thus have the formula: Energy = X * 28 * 4.18 = X * 117 in kJ we pass in kWh because it is what is invoiced 1 kWh = 3600 kJ

Energy = X * 117 / 3600 0.0325 kWh = X *

If X = L 50, so we consume * 50 0.0325 1.625 kWh =
If X = 150 L, then we consume 150 * 0.0325 = 4.875 kWh is the price of a dryer cycle that is said to be very energy efficient!

For an efficient shower, we can retain an average value of 2 kWh / shower.

We take the value of 3 kWh / shower for the rest corresponding to a 90L shower or a long shower (9 minutes opened tap)

c) Final bill average with hot water to electricity with a price of 0.2 € / kWh electric (Belgium): about 1 € / shower (0.5 € / economic shower and 1.5 € / long shower)

Price = price of water + price of water heating = 0.4 + 3 * 0.2 = 1 € / shower all battery.

The ventilation is also interesting: 40% of the price for water and 60% for the heating of water. I thought the share of heating would be higher ... especially that I took the electrical energy, ie the most expensive.

In heating oil it is about 0.1 € / kWh, for an oil shower, we are 0.7 € and the share of water costs more expensive than energy!

There would be a more global question to be asked for this particular case: renewable water costs more than exhaustible oil? Gee ...

In the end for a family of 4 people, the "shower" price alone (1 shower / day per person) can amount to 4 € / day and therefore 120 € / month, in short, it is starting to make money, especially at the moment! !

Being thrifty, we can divide this bill by 2 (0.5 € / shower) and go from 120 € to 50 to 60 € / month ... and 50 € / month is not nothing in the current household budget!

It would be perhaps interesting to pass the price with the variable "duration" in the shower to obtain a value of the price in € / minute of shower ... I would do it if asked after your remarks or suggestions.

[dirk pitt]

Oh well, I love these small order of magnitude calculations.
it fixes the ideas well.

[Christophe]

I also quite like! So you're welcome my dear Pitt! Should talk about it and share this topic now where you can ...

Because all the same 2 important info to remember:

a) nothing but the shower is a significant item on the bills (we always talk about the heating station neglecting a little else) because for a family of 4 people, the annual savings potential is over 700 € !! Just by paying a little attention ...

700 € is not nothing at all and it's money less for the lobbies of water and energy!

b) that for a shower (or a bath or even a washing machine or dishwasher, in short everything that uses hot water to 40 ° C, because the reasoning is the same) the "water" part also costs, or even more expensive depending on the case, than that of the energy for its heating!

[elephant]

What costs a bridge is hunting: from the moment I plugged ours into a pump (separate circuit: I have 2 arrivals on my toilet, not even a filter), I saw the difference: 50% because "these ladies" cannot stand the slightest trace of pee in the pot

My wife and I consume respectively 18 and 26 liters / morning toilet. the difference is explained by:

1) the hot water supply time from the 1er to the bathroom (4 to 5 liters that I get to rinse the sink)
2) beard

What makes me moan is that, not only, the water is actually 3,69 htva / m³ (including 1,54 of treatment fees), but in addition, there are two fixed fees: a subscription, a purification (50 € each). (Charleroi region)

100 € for the 1er liter. grrrrr.

A SWDE official told me that they lost about 50% in network leaks.

unrelated: I decided a few weeks ago to shave before the shower: no need to wipe the mist on the mirror ...

[Christophe]

elephant, a champion of applied econology !!

[Did67]

In general, hot water (also the "small dishes" in the sink, but also the "bad kids" who prefer to mix tap water to brush their teeth!) Can cost almost as expensive as the heating of a well-insulated accommodation for a family of 5 !!!

So yes, you have to hunt!

[Christophe]

Brushing teeth with hot water? Yuck ...
In addition there is a health risk with old balloons ...

Yes, live the hunt !!

[Did67]

I said "mitigate", so as not to have ice water (it is 9 ° with us) !!!

I did not say that I approved.

I specify that I am enraged all the more that it amounts to "emptying" the hot water pipe of all cold water over its entire length, to finally mix 1 / 5th of hot water with 4 / 5th of cold water, just to have water at 25 ° which is no longer frozen.

I reassure you, I fight !!!!!!!

[but still find the mixer lever in the "middle" position = cold water / hot water mixture; to note that this "mania" of having to put the lever completely to the right is not "aesthetic", therefore it facilitates the mania of putting it "right", therefore to mitigate, therefore to empty the hot water pipes for not great thing; sometimes even piur use of the ECS which never arrives at the end!].

But I struggle, I struggle ... If I quote that, it is because it seems to me probable that many "dirty kids" proceed like that and that one is not always aware of it (NB: the beautiful- mother too!). And that this is the height of absurdity, even if it is not a deluge of DHW either!

[Forhorse]

[but still find the mixer lever in the "middle" position = cold water / hot water mixture; to note that this "mania" of having to put the lever completely to the right is not "aesthetic", therefore it facilitates the mania of putting it "right", therefore to mitigate, therefore to empty the hot water pipes for not great thing; sometimes even piur use of the ECS which never arrives at the end!].

I also noticed that. It is for this reason that I decided not to install these dirty mixer. On the last sink I installed at home (as well as on the next) it's the old 2 faucets system.
it avoids drawing some hot water even when you want cold water because the controller is not completely right (something that in 98% of cases, we do not pay attention).

EDIT: I noticed this especially since the restarting of my ecowatt, the display is in the kitchen. With us in off-peak hours; the hot water tank is "live" and heats up as soon as the thermostat requests it.
This means that when you draw hot water, even a little bit, the arrival of cold water in the balloon starts heating for a few minutes.
And it's not uncommon for me to see the power consumed soaring right after pulling some cold water and to realize afterwards that the mixer was not completely right

[Did67]

I have not done yet, but I think another solution is, in any case with round sinks, put the mixer on the side, on an axis 45 ° from the bung; like that to have cold water, the lever must be straight towards you; to mitigate, in the direction of the bung and to have the hot water, it is necessary to put it parallel to the wall of the bottom!

In a way, virtually frame the sink of a square and put it in the right corner of this square ...