Electric shower v using combi boiler hot water - most efficient way to set it up?

I ended up posting about this on another thread and forgot to update this one.

I've now got my bath tap hose and after a bit of fiddling, found the best spot to fix the head to the wall with a suction bracket that I already had, so I showered using the combi boiler this morning.  It used 0.271m3 = 3.06kWh, costing 22p.  Not quite the saving I was hoping for.  I reckon that my usual 8 minute 9kW electric shower costs around 34p (9kW / 60 x 8 = 1.2kWh = 34p).  I estimate that it used about 20-25% more water - but I didn't have the taps at full pelt.  I kept the boiler water temp at 55°C and used a little cold too - I'll lower the boiler temp tomorrow and try just using hot, for comparison.

So it would take a very long time at 12p saving per day to recoup any installation expenditure.  There was a phenomena I wasn't wholly expecting.  I'm also monitoring my electric use after making other changes and this morning, I'd used a chunk more electricity than I was expecting, so I don't know if this is in part due to switching the electric shower on in case of mishaps, or more likely, that the water pump in the boiler uses more electricity than I'd expected to get the water to the taps.  The extra today certainly negated any saving I made in the water heating aspect of the shower.

I'll try some more tests to ascertain more accurate numbers - my method was a bit haphazard this morning as I futzed with water temp, shower head position etc.

northernsoul said:

Why have my spreadsheets been deleted. Is it against the rules ?

I have no idea - I don't recall seeing any 'spreadsheets' in this thread.  In your first reply to me you posted the costs of the various lengths of showers you'd tested - and those are still there.  I can't identify anything that appears to be missing from the thread.

No, life's too short to time such things.  I'd just been watching the clock recently to get an average for the purposes of doing some sums.   I've changed my methodology a little to try and cut down on the time I use running water.

Hence I said I was a bit haphazard this morning, as I forgot to look at the time.

That's pretty much my conclusion now @macman - I don't know if you've just read the OP and replied, but if you see my post from this morning earlier up this page, I did meter readings today using my bath tap hose and my very quick and dirty assessment is that it isn't likely to be the saving that I was hoping that it might be.  The boiler used more energy than I'd stabbed a guess at and the resulting cost was 22p for the same sort of shower - just for the heating of the water using gas. 

My testing method was a bit flawed today, so I'd need to do a few more to get better data, but it also looked like it used more electricity too - presumably for the pump supplying the water.  My numbers today suggest that it's pretty much break even - not quite the 'ditch electric showers' mantra often posted here for people wanting to reduce electricity bills.  Maybe it works out cheaper if using a water tank and not a combi boiler?

It wouldn't just be about saving the pennies on each shower, but comfort and style too. I want to get my bathroom re-worked at some point and this is something I'd include in those plans.  Although there is also a good argument to be made for having a different source for the shower water - I've been without a working boiler often enough to be glad that I could at least get a hot shower and use it to provide warm washing water in the bathroom.

I do at least now have my tap hose to give me the option, even if I now decide against a more permanently plumbed solution.  I've already saved some pennies by putting the plug in the bath and showering for less time and using the standing water for some of my in-shower tasks.