Working out charge for my storage heaters

Qyburn

If you get a cheaper tariff but with say only one hour afternoon boost, it might not be the end of th world if you sometimes need to use a bit of direct heat.

Rosie1001

Thank you all very much 

the plan is eco 10 if I can when the meter is changed , hopefully this will work 

if not .. I’ll try eco 7 

and possibly snug if it works out cheaper when it’s all done 

Scot_39

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?

Because tge temp profile would be a higher single core brick peak in the wee small hours - with a corresponding higher heat output via passive conduction, radiation and of course conve tion  - but possibly overridden by any use of vent flap timer mode for boosting convection later in day.

It's a complex dynamic mix of input setting and output setting, charge capacity and of course room demand.

If the op is nesrly always charging near her 7 hr max that's concerning  - as its really not that cold every day in winter - so the heaters are potentially well under sized for needs.

If the op is charging in afternoon - unless input high enough to still need all 2 hours every day - the chances are it's taking a large share of tge daily charge then too - around half on milder demand days if the full 2 hrs not required to replace lost charge arguably. 

Scot_39

QrizB said:

Rosie1001 said:

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 

"All they can" is 24kWh, which is how much they're intended to store (on effect, how many bricks they hold). If they've got 3.4kW heaters, it takes seven hours to fully charge them. 7 x 3.4 = 23.8.

Currently they're only charging for five hours overnight. 5 x 3.4 = 17. So only storing 17kWh.

Adding two hours of overnight charging will mean you store an extra 7kWh.

Whilst it is easy to get distracted by the max capacity - for many people storage heaters shouldnt be running at that capacity regularly if ever if properly sized.

And those who have posted their quantum diagnostics show the same - that their heaters are in general not taking the full charge on a daily basis.

In fact iirc some modern hhr -  are set to only take 80% on switch on iirc.  So 5.6 hrs not 7 - and adapt up and equally as likely in all but coldest days down from there as needed.

The "all they can" limit is one thing - the reality will depend on your ratings - suitable or not - settings and ambient temperatures / weather conditions governing heat gain (sun light on walls and through windows) and loss balance.

What they can take in theory is either a max of 7 hrs on a vanilla e7 single block timing or a max of 5 and then a max of 2 on your current.

But the reality is for a given core temp below rated limit needs - you are more likely to draw more energy - ratee power for longer - across 2 charge sessions than 1.  As the thermostat will restrict charging in one or both sessions. 

In my case as low user regularly all 3.

Apart from after initial switch on or a large adjustment upwards on input core temp dial - my heaters seldom run for the full charge periods - when can  hit the 2 hr limit.
 
But 

Rosie1001 said:

Yesterday I used 13 kWh on afternoon boost 

overnight I used 31 kWh 

so 44 kWh in 24 hours on my heat charge price 

My home is warm when I get up  at 5 am so definitely leaking some heat 

This is more concerning.  And far away from where I use my 3 nsh (actually just 2 since weather turned milder in last week cf earlier -vd days and nights). 

So ignore my low use biased ramblings above. 

That's really just not your current position.

Your 13 kWh is approx saturated 2 heaters x assumed 3.4 kW rating x2 hrs - 13.6 kWh - pretty much full time.

Your 31kWh / 13 x 2 = 4.8 hrs on a pro rata basis - with rounding close to the full 5 hrs.

Or 31/2x3.4 = 4.5 hrs.

If you need that yesterday / today when cold but not excessively so - how we're you coping when it was like 0 to -2 day highs and -4 to - 7 type night levels - at least here in  EM  - for few days  in recent weeks - about 6 deg colder than cucurrent.

And again with daytime highs in next few days of c10C forecast here what will your energy use charge balance be then night vs afternoon etc.

 
[For instance the Dimplex sizing calculator iirc assumes -3C external and recommends changing to -5 for Scotland.  And defaults to 21C for a living room, 18 others iirc last run I did.  Colder room target e.g. 18, warmer outside - like today's forecast c2C min, c6C high here -  it should not be being set / used at its full energy storage capacity.
Change that -3 to 4 - and my energy so charge power rating power needs for 1 room literally halves given large patio door type window losses in my mid terrace lr on their calculator.]

Your heaters are likely going to be a bit colder by 3pm without your 13kWh boost meaning less heat from them unless you can rebalance output using air vent damper "output" control timing. 

As the additional 13kWh will make your heaters even warmer than current by say 7am on e7 than are at say 5 am after a 5 hr charge window and would be cooling for 2 grs already.  So they will ouput more energy to room before 1 pm - if you like a loss or leak if undesired - and continue to drop temp to 3pm unlike current reheat and matching near total capacity charge input give above figures would have matched) - and beyond.

But if you can keep heat in room - from morning charge - you might be OK.

But open a window or door to outside for any significant period - so lose a lot of heat midday - you will be more likely to struggle by evening.

Rosie1001

Scot_39 said:

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?

Because tge temp profile would be a higher single core brick peak in the wee small hours - with a corresponding higher heat output via passive conduction, radiation and of course conve tion  - but possibly overridden by any use of vent flap timer mode for boosting convection later in day.

It's a complex dynamic mix of input setting and output setting, charge capacity and of course room demand.

If the op is nesrly always charging near her 7 hr max that's concerning  - as its really not that cold every day in winter - so the heaters are potentially well under sized for needs.

If the op is charging in afternoon - unless input high enough to still need all 2 hours every day - the chances are it's taking a large share of tge daily charge then too - around half on milder demand days if the full 2 hrs not required to replace lost charge arguably. 

My partner is 70 and feels the cold , and I personally like a really warm home … so yes they are on high until around end of February 

and I live right on the coast so get North Sea cold winds 

Comfort in the home varies from person to person , it’s just how we prefer it 

my sister for example likes her rooms cool , I couldn’t stand that ! 

Scot_39

Rosie1001 said:

Scot_39 said:

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?

Because tge temp profile would be a higher single core brick peak in the wee small hours - with a corresponding higher heat output via passive conduction, radiation and of course conve tion  - but possibly overridden by any use of vent flap timer mode for boosting convection later in day.

It's a complex dynamic mix of input setting and output setting, charge capacity and of course room demand.

If the op is nesrly always charging near her 7 hr max that's concerning  - as its really not that cold every day in winter - so the heaters are potentially well under sized for needs.

If the op is charging in afternoon - unless input high enough to still need all 2 hours every day - the chances are it's taking a large share of tge daily charge then too - around half on milder demand days if the full 2 hrs not required to replace lost charge arguably. 

My partner is 70 and feels the cold , and I personally like a really warm home … so yes they are on high until around end of February 

and I live right on the coast so get North Sea cold winds 

Comfort in the home varies from person to person , it’s just how we prefer it 

my sister for example likes her rooms cool , I couldn’t stand that ! 

Yes it wasn't  really meant as an attack on the temp and how you use your heating - just your ability to maintain it to desired level with those heaters.

Basically if charge for 7hrs or near enough you are hitting a sizing problem.

Anc so may not achieve your target temps on colder days (no thermal gain, windy, damp etc all plag a part) 

I am a lot less likely to just because run a colder set of room temps.

But if you want or need say 21 rather than 18 for comfort or health - then you need heaters capable of delivering it in reasonable worst not typical average winter outside weather.

My neighbours - a few years ago-  elderly couple needing high temps - had 2 qautums to replace one xlsn equivalent unidare wms24 like mine being het 3x per day for upto 10 hrs in theory - because they struggled in first e7 winter - relying on pkug ins by late evening at peak rates eating up e7s cheaper off peak unit rate.  And the suppliers sizing calculator likewise said the modern replacement - a non rf qm150 charge was't good enough to guar 21C on coldest days from only e7 off peak.  Iirc Fitted two smaller - maybe 31kWh combined store from 2x 100s vs 23kWh from 1 150 iirc. 

Rosie1001

My home is very warm I have to say with my 5 hours and 2 hour afternoon boost 

and I use an electric blanket 

I’ve never liked the cold , I’m definitely not a typical Geordie lass  going out with no coat on 

I even asked for a extra blanket on holiday in Dubai , they looked at me like I was crazy ha ha