Combi or Electric

[Wontdothatagain]

Which is cheaper to run, a 8.5KWH shower or a combi boiler supplying and mixer head????

 

[flameport]

In terms of heating the same volume of water, gas is cheaper.

However the flow and performance of an 8.5kw electric shower is nothing like a mixer shower on a combi boiler.

 

[JohnW2]

Which is cheaper to run, a 8.5KWH shower or a combi boiler supplying and mixer head????

It obviously varies but, on 'standard tarifs', I think that electricity may typically cost around 12p per kWh and gas about 4p per kWh - so there's really no contest (not that showers amount for a significant part of most people's fuel bills). I don't really understand electric showers being so fashionable - not only more expensive to run but also 'inferior' (flow etc.).

Kind Regards, John

 

[Wontdothatagain]

Many Thanks both.

We only have electric at home as we are out in the middle of no-where so i am not sure about gas prises and consumption to achive the same effect.

 

[JohnW2]

Many Thanks both. We only have electric at home as we are out in the middle of no-where so i am not sure about gas prises and consumption to achive the same effect.

You're welcome. I'm also 'in the middle of nowhere', with no natural gas supply, but we use LPG. Although a lot more expensive that natural gas, it's still cheaper than electricity for heating home/water.

Kind Regards, John.

 

[sparkticus]

Many Thanks both. We only have electric at home as we are out in the middle of no-where so i am not sure about gas prises and consumption to achive the same effect.

You're welcome. I'm also 'in the middle of nowhere', with no natural gas supply, but we use LPG. Although a lot more expensive that natural gas, it's still cheaper than electricity for heating home/water.

John, does LPG have a higher caloric value than natural gas? If so does that help offset the cost or have you already factored that?

 

[JohnW2]

John, does LPG have a higher caloric value than natural gas? If so does that help offset the cost or have you already factored that?

Yes, LPG has a much higher calorific value than natural gas - around 26 kWh/m³ as compared with (I think) only about 10-11 kWh/m³ for natural gas. Unfortunately, the cost comparison I was talking about was in terms of cost/kWh - so the considerably higher cost of LPG is only too 'real'.

One upside of the high calorific value is obviously that storage tank size can be smaller - and my 2000 litre one is big enough! Another significant difference is that LPG flames are much hotter - so, for example, unless one uses 'flame failure' thermocouples specifically designed for LPG, they burn away very quickly!

Kind Regards, John.

 

[ericmark]

Although the gas boiler is likely 30kW compared with best electric at 11Kw so while running it uses more power. To try to wash under the drips from an electric shower must take a lot longer then washing under the spray of a gas powered shower. And same for direct gas powered v stored hot water and a pump which can according to model produce a really powerful shower.

I would guess if one put in the plug all would use same amount of water but the time taken for a man to shower would vary. I say man as we tend to shower to get clean. Woman is another beast and I have never worked out how they can get so dirty that they need to shower for so long. And also the better the shower the longer it seems to take.

But back to reality I would only fit an electric direct shower when there is no option of using a gas heated one.

 

[Wontdothatagain]

Another significant difference is that LPG flames are much hotter

I have enougth problems wit Mrs WDTA burning the dinner allready so wont be going down that route

 

[JohnW2]

Although the gas boiler is likely 30kW compared with best electric at 11Kw so while running it uses more power.

What you can't get away from is that increasing the temperature of a certain volume of water by a specific amount will require the same amount of (output) energy (kWh), regardless of the form of heating - or , if you prefer, increasing the temperature of water flowing at a given rate by a specific amount will require the same (output) power (kW), regardless of the form of heating.

But back to reality I would only fit an electric direct shower when there is no option of using a gas heated one.

As I implied before, I would definitely agree with that.

Kind Regards, John.

 

[timbim]

What you can't get away from is that increasing the temperature of a certain volume of water by a specific amount will require the same amount of (output) energy (kWh), regardless of the form of heating - or , if you prefer, increasing the temperature of water flowing at a given rate by a specific amount will require the same (output) power (kW), regardless of the form of heating.

From a theoretical point of view, the direct electric heating probably the most efficient system imaginable, since gas heating has the losses of not capturing all the heat from the combustion and losing heat in pipework and storage tank; and the conversion of energy into heat in the element of the electric shower is as near 100% as we'll ever get.

That said, in practice you'll probably end up taking a longer shower with the electric because it's a bit pathetic, eliminating any gains made. The pipework losses in the case of a gas system are only really relevant in summer anyway, as in winter it'll be relieving the central heating.

I certainly wouldn't use an electric; pair of gas boilers, stored hot water and a large pump make for a very good system.

 

[JohnW2]

What you can't get away from is that increasing the temperature of a certain volume of water by a specific amount will require the same amount of (output) energy (kWh), regardless of the form of heating - or , if you prefer, increasing the temperature of water flowing at a given rate by a specific amount will require the same (output) power (kW), regardless of the form of heating.

From a theoretical point of view, the direct electric heating probably the most efficient system imaginable, since gas heating has the losses of not capturing all the heat from the combustion and losing heat in pipework and storage tank; and the conversion of energy into heat in the element of the electric shower is as near 100% as we'll ever get.

Indeed. I probably wasn't as clear as I should have been, but when I spoke of energy and power output, I intended that to mean 'effective output' (i.e. transferred to the water) - and I obviously agree that efficiency will be near-optimal with an electrical shower and appreciably less with a gas boiler. However, the price differential between gas and electricity (per kWh) is so great that I imagine that gas retains a cost advantage in terms of a given amount of water heating.

I certainly wouldn't use an electric; pair of gas boilers, stored hot water and a large pump make for a very good system.

Indeed. In fact, although I was initial sceptical, I've also experienced some quite impressive showers run from 'instant gas heating' (i.e.combi boiler).

Kind Regards, John.

 

[jabuzzard]

But back to reality I would only fit an electric direct shower when there is no option of using a gas heated one.

What do you do then when your combi boiler breaks down? No bath and no shower makes for a smelly person. Personally I would only fit an a shower that was fed from a combi boiler if I had another shower that was electric.

 

[flameport]

Combination boiler = no hot water when it breaks. Typically fitted due to it's lower cost, or when people can't be bothered to spend slightly more on a proper system.
Electric shower = no shower when it breaks. Typically fitted due to it's lower cost or when people can't be bothered to fit a proper shower.

Therefore don't bother with either.
Gas boiler (or oil if no gas available) and hot water cylinder, which also has an electric immersion heater for when the boiler breaks.

 

[Stoday]

Gas boiler (or oil if no gas available) and hot water cylinder, which also has an electric immersion heater for when the boiler breaks.

Yes, provided the cylinder is unvented, so that your hot water is at mains pressure.

The old system using a cold water cistern feeding a low pressure cylinder is obsolete and will limit your choice of sanitary fittings that use hot water.