Cost of using immersion heater on boost for an hour (not on Economy 7 tariff)

rbh

After a very costly gas boiler replacement and other system upgrades failed to make our heating system work (it's a sprawling Victorian house) we had it taken out in 2010 and a new electric dual  immersion heater put in which is the only means of heating water. I only heat the hot water on boost (top element) for an hour for a bath in the afternoon when I've finished manual work for the day and I try to do that only every 3 days now to save money. I get enough piping hot water to cover my legs, not a full bath. I'd hoped to heat the lower element (full tank) overnight on Economy 7 but I found that was not only wasteful  it would go cold before I could use it) but crucially the water didn't get anywhere near as hot for my bath as using the top element. That could be because I use the hot water for the bath round 9 hours after it had heated overnight. It cost a bomb to heat the whole tank during the day when I tried it. I went onto standard rate tariff instead of Economy 7 as using it overnight didn't work and there's only the fridge and freezer running at night. I now live alone & have very little money coming in and I'm fearful of the impending hike in electricity costs. Trying to make even more savings! I've tried lowering the thermostat on the top element but any lower doesn't get hot enough for my bath. 
Can anyone tell me if the boost facility costs more than setting the timer for an hour during the afternoon? They're fiddly, but I can set the timer clock if necessary (there's one for each element). As I don't ever use the lower element, does it matter what the thermostat on that one is set to? 

lohr500

If the boost button works on the upper element for an hour, you will use the same amount of electricity as setting the timer on the upper element for an hour. The heater uses the same power for the boost function as the timer function.

The boost button is really there to supplement the hot water heating in an Economy 7 set up. Normally the bottom element would heat the whole tank on Eco 7 and you would use the boost facility on the top element if you needed some extra hot water due to heavy demand through a particular day.

It is a bit academic now as you no longer have Economy 7, but perhaps the lower element thermostat was set too low resulting in the water not being warm enough for you. Also how well insulated is the immersion cylinder. If well insulated, the water heated up on Eco 7 should have kept warm enough to take a bath 9 hours later. 

What tariff are you on now and which region do you live in? By switching to a standard rate tariff you are heating the water in a very expensive way. How is the rest of the house now heated if you removed the very costly gas boiler replacement in 2010? 

QrizB

rbh said:

Can anyone tell me if the boost facility costs more than setting the timer for an hour during the afternoon?

If they both run for an hour, the price will be the same.

At the current capped variable rate and assuming the normal 3kW immersion heater, one hour will cost about 63p (potentially less if the water reaches its target tempersature before the hour is up).  From the 1st of April it will be about 84p.