Energy cost for having a shower versus having a bath

raina11

Can anybody tell me whether it’s cheaper to have a 10 minute shower or to have a 1/2 filled bath? Many thanks. 

Bendy_House

What type of shower? Electric 'instant'? From a vented CWS in t'loft? With or without a pump? From an unvented - mains-driven - cylinder?

Rodders53

What flow rate is your shower head in litres per minute?  What energy source for the shower (electric instant, gas combi, etc..,.) ?
What dimensions is your bath tub inside (how many litres does it hold) to the "half full" level?  What energy source for the hot water?

Google it and US sites suggest a 10 minute shower uses 25 US gallons and a bath may be 25-35 US gallons...  so probably no significant difference in water use for a half bathful?

So similar for the energy used for hot water... unless source one is heated by gas and the other is electric... in which case gas wins as cheaper (usually).

casper_gutman

If the shower is over the bathtub and uses water heated in the same way (e.g. by your main boiler) then the easiest way to see the difference is to put the plug in and take a typical shower. If the amount of water in the bath when you're done is too little to bathe in, then a shower is likely to be the best option. If the bath fills to overflowing and floods the house before you're done, then a bath is probably better!

Belenus

What are you doing in the shower for ten minutes?

I have a daily shower but I'm probably out in about four minutes or less.

EssexExile

Belenus said:

What are you doing in the shower for ten minutes?

I have a daily shower but I'm probably out in about four minutes or less.

My wife can empty the hot water tank taking a shower!

Belenus

EssexExile said:

Belenus said:

What are you doing in the shower for ten minutes?

I have a daily shower but I'm probably out in about four minutes or less.

My wife can empty the hot water tank taking a shower!

Count yourself lucky.

My wife can empty a bank account taking a shopping trip. 

Rdwill

Here's a go on a fag packet.

According to United Utilities

https://www.unitedutilities.com/your-questions-answered/bills-payments/what-does-a-litre-or-cubic-metre-of-water-cost/

A cubic metre equals 1,000 litres of water, this is equivalent to 28 showers or 13 baths and water costs about £3 per m3.

So a bath would cost you £3 / 13 = 23p in water and a shower would cost you £3 / 28 = 11p in water.

Our shower runs on about 12kwhs, so at 30p per Kwh, a 10 minute shower would cost 12kwh x 30p = £3.60 (to run it for an hour) / 60 x 10 mins = 60p in electric. So a 10 min shower would cost 60p +11p =71p.

The cost of heating the water for the bath is a bit more difficult

(I have solar panels that heat the water in the tank, so I don't bother with this part of the sum).

So in my world 10 min shower = 71p, bath for as long as you like in 77 litres = 23p

But to have a go at completing the comparison

According to

https://bloglocation.com/art/water-heating-calculator-for-time-energy-power

To heat 77 litres of water from 7 Celsius to 37 Celsius uses 2.69kwh of energy, assuming 100% efficiency (ie you use the immersion heater) which means that heating the water would cost 2.69Kwh x 30p =  81p.

So cost of bath water plus energy (assuming electric immersion) = 81p + 23p = £1.04

Bath would definitely be cheaper to heat if you used gas, but that sum is definitely on the too difficult pile, as you need to look at the efficiency of the boiler and pipe run  to the tank, wear and tear servicing on the boiler etc etc.

casper_gutman

The unstated assumption in @Rdwill's post is that the shower is electric.

The ex-physics teacher in me is itching to put a big red circle around the bit that says "our shower runs on about 12 kWhs" and reword it to "our shower has a power of about 12 kW, so running it for an hour would use about 12 kWh of energy" but the end result is the right calculation so I'll leave it! 

twopenny

There's a calculator on some water websites. However I prefer two do it myself with mseasuring jugs.
A 12min shower is long. I would doubt there's much difference.
Keep in mind there are different size baths.
An acrylic bath with insulation will keep the water hot for a long bathing session.
A steel bath will suck the heat out straight away.
If you have a  big bath and you are 2ft/3ft laying down you need more water and heat.
Needs more technical detail.

Sapindus

We are told this repeatedly by the water companies et al, that a shower is cheaper and uses less energy.  I am pretty sure that I use more energy since I switched to a shower, for the simple reason that the shower is so much easier to pop into that people have one every day or even twice.  I didn't have a bath every day.  Once you've run the bath, it doesn't take any more energy the longer you spend in it, apart from a bit of topping up.  If you get in the shower wanting to relax, it just goes on and on eating water and electricity.

When I was a kid, bath night was once a week.  Hair could be washed in a bucket over the bath, and bodies could be washed standing at the sink.