Showers, is it cheaper to have electric shower or from gas boiler?

Petriix

It's even more complicated for those of us on Octopus Go. An electric shower in the off-peak period is 5p per kWh while gas is now (7p at ~ 80% efficiency) 8.75p per kWh. But, I already blew ~ £100 on swapping out my old electric shower for one fed from the combi boiler last year.

Ideally I'd have a well insulated water tank which could be heated by a solar diverter and/or in the off-peak window. But there isn't a way to make this play nicely with our existing boiler. So I'll have to suck it up until the boiler needs replacing and then look at the options.

QrizB

BooJewels said:

Electric showers vary in their flow and consumption - even the shower head can make a difference - but gas powered showers have even more variables on top.

There's a fundamental difference between electric showers and those fed from the hot tank via some sort of mixer.

The power drawn by electric showers is constant (unlkess you have two heat settings, in which case each of those is itself constant). The temperature is directly related to the water flow rate. Reducing the flow makes the shower hotter, increasing it makes the shower colder, but the electrical power used does not change.

One common error with an electric shower is to replace the head with a different one in the hope of getting more flow. Yes you get more flow but you also get a colder shower! Electric shower heads are matched to the shower by the factory.

In the case of mixer showers, you *can* vary the flow rate independently of the temperature and so you can reduce the energy needed by reducing the flow.

BooJewels

@QrizB - when I said that showers vary in flow and consumption, I didn't mean an individual shower does that - but from one model to the next - yours might be a higher spec than mine - which is failry basic. 

Meaning that it's not as simple as to compare 'an electric shower' to a boiler or tank fed one - as not all electric showers are the same to start with.  As I understand it, as you stated, if you have a 9kW shower, as mine, it still uses that power, but when at a cooler setting, you just get more water and at a hotter setting your flow drops and you get less.  Obviously the starting water temp makes a difference too.  I get slightly better flow in summer when the start temp of the water is that bit warmer.  

QrizB

BooJewels said:

@QrizB - when I said that showers vary in flow and consumption, I didn't mean an individual shower does that - but from one model to the next - yours might be a higher spec than mine - which is failry basic. 

Yes, I was agreeing with you and expanding on your point

Crazycatlady2

BooJewels said:

Crazycatlady2 said:

We have both in seperate bathrooms. I make everyone use boiler fed one now and other will be changed when we can

in house metre jumps from about 23p to over £2 last time someone used elec one

Perhaps you need to discourage that showerer from not being in there for 42 minutes then - that's 6.3kWh - even I can't take that long!  (assuming a fairly average 9kW shower).

Trust me I’m outside shouting hurry up 😂

BooJewels

Crazycatlady2 said:

BooJewels said:

Crazycatlady2 said:

We have both in seperate bathrooms. I make everyone use boiler fed one now and other will be changed when we can

in house metre jumps from about 23p to over £2 last time someone used elec one

Perhaps you need to discourage that showerer from not being in there for 42 minutes then - that's 6.3kWh - even I can't take that long!  (assuming a fairly average 9kW shower).

Trust me I’m outside shouting hurry up 😂

You could just try switching it off.      

My husband used to threaten that if he felt I was in there too long.   In one of the armed forces (navy?) they used to call showers longer than 4 minutes a 'Hollywood' - he reckoned I took 'triple Hollywoods, via the scenic route'.

Ultrasonic

BooJewels said:

That was rather my point (and I'd mentioned it in at least 2 posts before you started querying my facts)  - it's like comparing oranges to apples.  Unless the flow rate and temperature match like for like, it's not that easy to make a direct comparison of energy use, especially if you then factor in metered water and drainage too.  The headline fact that gas is less than a third of the price of electricity is misleading in this regard - yet it's cited very frequently in this forum as a reason to ditch electric showers.

Electric showers vary in their flow and consumption - even the shower head can make a difference - but gas powered showers have even more variables on top.

To answer the very simple question posed in the subject line of this thread - "it's not that simple - there are so many variables".  I would generalise that gas powered showers are probably, on balance, a bit cheaper, but possibly by not as much as you'd think.  But I'd also guess that they're more enjoyable too.  That was certainly my own experience.

Whilst there are other variables I don't agree that focusing on the headline difference in gas and electricity prices is misleading (assuming a combi boiler). This is the key difference that makes gas the cheaper option, and is independent of issues like taking longer showers or using higher flow rates also impacting cost. I think your personal example more reflects choices you made in how to shower differently rather than fundamental differences between using gas or electricity to heat the water.