electric shower vs timer

arrianalexander

hi question.

i live in an appt...it has main bathroom and an ensuite.

the water is heated over night on night saver...

my question is would it be cheaper in long to install two electric showers and turn off the night saver thing (sorry im sure there is a better word)

our bill for last two months was 141...my theory is alot of this is waste and unused hot water and then days where water is needed for showers etc we end up having to boost it...

i might be completely wrong in my theory but someone told me they installed 2 electric showers...and turned off the timer and their bills shot down

Dardania

generally, no, however to check two items:

are you on a nightsaver electrical tariff? (Should say it on the bill) What's is the night unit consumption vs. the day shown on the bill?

Is your cylinder well insulated with foam, or a lagging jacket?

arrianalexander

its well insulated..its solid like... and yes we are on night saver

cast_iron

arrianalexander wrote: »

its well insulated..its solid like... and yes we are on night saver

And his most important question you didn't answer

What's is the night unit consumption vs. the day shown on the bill?

Dardania

cast_iron wrote: »

And his most important question you didn't answer

What's is the night unit consumption vs. the day shown on the bill?

Yeah, the reason I'm asking this is to see if your time signal from the ESB is correct, or if your contactor internally might be shagged in the on position...

arrianalexander

ok here are reading from last bill
day 44395 - 44796
night 58788 - 59369

Bruthal

It is certainly more efficient to use an electric shower to heat only the water used, than to heat the hot water cylinder to use that for showers, and even more so with power showers using the stored hot water, as they have a higher flow rate. But whether this would be reflected in heating the cylinder at night time rates compared to daytime use of an electric shower would be hard to say.

How long each night would the immersion heater be on for?

Dardania

arrianalexander wrote: »

ok here are reading from last bill
day 44395 - 44796
night 58788 - 59369

so, over two months
day: 401kWh
night: 581kWh

nighttime represents 59% of your consumption

presuming you have negligible non water heating consumption overnight, you are using ~9kWh per night, which represents a 1kW load continuously as the night period is 9 hours long.

Personally, that feels to me that your night time load seems fine - in my last apartment where we had electric water heating, 2 months of our nighttime consumption was 593kWh - virtually identical to you. Our day consumption was lower than yours at 248kWh. Maybe daytime consumption could be optimised?

Things to double check to optimise your water heating:
what is the thermostat on the side of the cylinder at? Should be 60 to 65
At 11 o clock at night or 12 o clock at night, do you hear a contactor click in the electrical consumer unit? Do you hear it click off at 8 or 9am?
Are there any storage heaters in the house? Are they switched off at the wall?
How is the immersion controlled? Is it an E7 time clock?

You could also make sure to submit regular meter readings to ensure it is accurate consumption.

Regarding efficiency as against electrical instantaneous...

An average instantaneous shower has a 9kW load. Assume 30 mins of usage per day, so that's 4.5kWh per day. However, this must be doubled, as the nightrate is half the price of day rate, so it about evens out for unit cost.
The standing charge for day/metering is slightly higher than 24 hour metering.

So, in summary, if you shower for 35+ mins per day, day/night metering is better. If less, then maybe 24 hour metering would be better, based on your current configuration

By the way, you should note that you can't run two instantaneous heating showers at the same time...

cast_iron

Dardania wrote: »

So, in summary, if you shower for 35+ mins per day, day/night metering is better. If less, then maybe 24 hour metering would be better, based on your current configuration

I'm glad you did all the leg work
I agree with it.

The other thing to note is if you go instantaneous electric shower only, you may well have no hot water at your disposal at the various sink taps throughout the day/evening depending on your heating setup (which prob won't be on at all during the summer).
This could be solved by putting the sink immersion on for a bit, and that's additional cost to be factored in.

Bruthal

Dardania wrote: »

presuming you have negligible non water heating consumption overnight, you are using ~9kWh per night, which represents a 1kW load continuously as the night period is 9 hours long.

It would be very inneficient for a 3kw immersion heater to be using 9kw in a 9 hour period though.

Dardania

robbie7730 wrote: »

It would be very inneficient for a 3kw immersion heater to be using 9kw in a 9 hour period though.

That's why I was asking about the theremostat, and the controller....something might be locked on.
Alternatively, the insulation may be crap. The OP did mention they needed to boost during the day...

If it's an E7, the OP can look at: http://www.boards.ie/vbulletin/showpost.php?p=57702908&postcount=5

creedp

cast_iron wrote: »

I'm glad you did all the leg work
I agree with it.

The other thing to note is if you go instantaneous electric shower only, you may well have no hot water at your disposal at the various sink taps throughout the day/evening depending on your heating setup (which prob won't be on at all during the summer).
This could be solved by putting the sink immersion on for a bit, and that's additional cost to be factored in.

This is the big disadvantage I see with electric showers - because the immersion is not used for showers there is a tendancy not to have hot water for the sinks, which is a pain. A couple of people I know have this set up and consequently there is never any hot water in the bathroom/kitchen sinks. Maybe I should cop onto myself but it is one luxury I like to maintain in this environmentally friendly/recessionary time:)