Electricity bill - calculating costs

[adwt2004]

I have economy 7 and I currently get charged 4 pence per unit. I am trying to work how to calculate the units used for an immersion heater (3kw)

If i had this running for two hours everynight during economy 7 and roughly say that a quarter is 90 days. How would I work out the cost? I've tried a few methods but hopefully someone understands it better than me and can advise! I worked it out to about £35 a quarter but if some one could tell me the correct way of calculating i'd be grateful!

 

[judder]

Well, from what you've written, 3kw for 2 hours gives 6kwh of energy per day. 90 days of this usage = 540 kwh. If when you say 4p per unit, you mean 4p per kwh, then for 90 days the charge should be 540 kwh x 4p per kwh = £21.60.

 

[big-all]

as judder says bbuuutt

once the temperature is reached it will cut out

so assuming the water is tepid to warm i would think about half that amount
as in 45mins on full to get to temp then 5 mins every 20 to top up

but that is purely a guess as to heating times and consumption to "top up " afterwards

the most important thing is lagging on the tank and setting the thermostat propperly
and the time switch to heat the water as late as possible

 

[adwt2004]

Thanks guys, great advice, just want to make sure the bill isn't extortinate. Wasn't sure whether to have gas installed or not. (not on supply at present) thanks for your advice

 

[adwt2004]

Do you think if i heated the water between the hours of 5-7 on a morning the water would still be hot say 9pm at night if i used an economy 7 spec cylinder with a jacket also? The water wouldn't start being used until about 7pm onwards

 

[big-all]

Do you think if i heated the water between the hours of 5-7 on a morning the water would still be hot say 9pm at night if i used an economy 7 spec cylinder with a jacket also? The water wouldn't start being used until about 7pm onwards

depends on insulation tank size and whether you use it or not and what you want to do with the water

iwould suggest if properly insulated around 90% heat will still be avalable 12hrs later enough for perhaps 2 normal showers the washing machine and the dishes
at this point your water is still warm but not hot enough for much more than washing hands

apart from that the length of the pipes can waste heat [around 2L in my kitchen]


all the above are dependent on so may variables so best experiment and note what you get out of a tank[emersion]

and for example if you would waste 4L of hot water because thats what the pipes to the kitchen contain you could boil a kettle for the dishes

or plan to do the clothes and dishwashing at the same time so you only waste 4L once [assuming they are close by]