Working out charge for my storage heaters

Rosie1001

As you all know , I’m fighting to kept my afternoon boost as I think I need it 

but …. Do I ??

my heaters are dimplex box of bricks style 

Both 3.4 kw 

I currently get 5 hours overnight 2 hours afternoon boost 

economy 7 would give me 7 hours overnight , no afternoon boost 

I’m presuming the heaters will only take some much charge before stopping 

will the 7 hours overnight be enough ???  Or do I really need the extra boost mid afternoon

I go to bed around 8.30 most nights and up at 5 am every day 

I have no idea how to work this out 

any help would be appreciated 

lohr500

Do you know the model numbers? 

I'm not sure what the 3.4kW refers to, but it think it is probably the m\ximum current draw when charging.
To work out how long they take to fully charge, we would need to know their rated maximum storage capacity.

As an example, if the storage heater had a rated capacity of 18kWh, it would take 18 / 3.4 = 5.3 hours to fully heat up assuming it was cold at the start of the heating period.

My understanding of the afternoon boost period is that it is useful for householders who like to have heat from their storage heaters throughout the day, rather than just later in the day.
And also useful for those with older style storage heaters like yours that don't store their heat as efficiently and tend to "leak" heat during the day when it is perhaps not needed.

If your heaters were 18kW versions, then the 5 hour slot would just about fully reheat them based on my earlier calculation. But then if you had them running through a cold day, giving out say 2kWh of heat each. they would only last 18/2 = 9 hours before going cold. A 2 hour boost in the afternoon would give you another 3.4 hours of heat at 2kWh.

Rosie1001

One is a  XL24  the other one is a XLN 

both got 4 elements inside  and are 850kw each 

mine are older style and do leak heat …I’m up early thou so this isn’t a issue for me 

In the  winter they are on constantly … 

lohr500

OK, so assuming the XLN is also the 24 model, they are both designed to store 24kWh of heat.

At 3.4kW input that means they need 24/3.4 = 7 hours to fully reheat from cold.

So they won't be fully heated up on the 5 hours overnight.But will then get 2 x 3.4kWh = 6.8kW boost from the the 2 hours in the afternoon.

If you are using them all the time through the winter at lets say at 2kWh output each, then each of them will run out of heat after 24/2 = 12 hours.

If you move to a regular single 7 hour off peak tariff, which ends at say 7am and start using them from 7am onwards, then they will be cold by 7pm. Probably a bit less actually as they will be losing some heat through "leakage" during the 7 hour reheating period. 

Rosie1001

Thank you very much for your help , much appreciated 

so I do need my afternoon boost , that’s very helpful 

QrizB

Rosie1001 said:

so I do need my afternoon boost

I think those calculations aren't correct and might have given you a wrong answer.

Your storage heaters currently get five hours of overnight charging and two hours of afternoon boost. In total, then, they charge for seven hours, enough to add 24kWh each and last through your day.

On E7 they would get seven continuous hours of charging, enough to add 24kWh each. I don't see why those 24kWh won't last the whole day in exactly the same way as your current 24kWh do.

How much cheap-rate electricity have you used in the past month? What does your latest bill say? How much heat are you actually using?

Rosie1001

I’ll post my last bill for you 

Rosie1001

This is from last may until Xmas time … bare  in mind the heating was  off until around oct 

I get a refund on standing charge as I pay only one for 2 mpans 

Rosie1001

My night consumption is around 8500 kWh per annum 

Rosie1001

QrizB said:

Rosie1001 said:

so I do need my afternoon boost

I think those calculations aren't correct and might have given you a wrong answer.

Your storage heaters currently get five hours of overnight charging and two hours of afternoon boost. In total, then, they charge for seven hours, enough to add 24kWh each and last through your day.

On E7 they would get seven continuous hours of charging, enough to add 24kWh each. I don't see why those 24kWh won't last the whole day in exactly the same way as your current 24kWh do.

How much cheap-rate electricity have you used in the past month? What does your latest bill say? How much heat are you actually using?

Would my heaters continue charging for full 7 hours on eco 7 where is it’s all in overnight charge ??.

do they not just take all they can and stop charging 

Rosie1001

This is just my heat part of my bill 

the other mpan  for normal electric is billed separately 

It’s not normally done like that , I get one bill with both on it , set out for each Mpan