Electric heater in one room vs centrally heated whole house

aelitaman

DemiDee wrote: »

Cardew, I guessed as much regarding the name of the electric heater. However, this one does seem extremely energy efficient. It's a 1.5kw heater. The info about using just one or some of the radiators and switching others off being less cost effective came from an e.on rep who seemed very knowledgable. Unfortunately, it's not as simple as just switching them all off and using the one in the office, since this one's only very small and doesn't give off much heat unless the rest are on too, so it's been an 'all or nothing' situation for some time.

HappyMJ (love the username!), I'm not anywhere near having used the higher ratings. My bill goes from 30th November, and there's a long way to go before I reach the amount needed to get onto the reduced rates.

This is an interesting comment on the small radiator not getting hot when all the others are turned off.

The explanation for this could be that how a central heating system is designed is to have a thick 22mm ring of copper pipe that the radiators are dropped off using 15mm. The boiler works by sensing the return temp of the water in the thick ring and when it is returning at a set temp (hot) the boiler will switch off the burner and stop heating the water. So if because all the radiators are turned off bar one it means that the returning water temp gets up to the required temp quickly then not enough hot water has flowed to the small radiator, hence not enough heat disipated in the room to warm it up.

So the solution is to turn on more radiators so that the water takes longer to hit the temperature that the boiler stops heating the water so that more hot water flows through the small radiator so warming the room sufficently.

flashnazia

molerat wrote: »

44-48p is ridiculous. At the coldest I was using 15p per hour heating my whole 3 bed detatched, including keeping the conservatory warm, 24/7 using my 25 year old boiler, the same as a 2Kw electric heater.

How do you reach the 44-48p figure ? Check your meter for m3 or ft3. If you are using the wrong figure your calculations will be 3 times what they should.

48p /hour doesn't sound ridiculous to me. I think it sounds right. 15p/hour sounds very low.

Robert2009

Right, this is how to work out how much you are paying per kWh of gas if you are on a 2 tier tariff.

Say you use 19000 kWh of gas a year

Your tariff is first 2680 per year is .065247 pence which is £174.86

Then you have 16320 kWh at .031584 pence which is £515.45

Add them together which is £690.31.

Take off any discount which in my case is 24.4% equals £168.44 which gives a cost of £521.88 for 19,000 kWh

Divide £521.88 by 19,000 which gives 0.027467 pence, round it up to 3 pence.

I was using 120 kWh a day for 24 hours which gives 5 kWh per hour

5 times 3 pence gives 15 pence per hour.

I used 7277 kWh of gas in the past 90 days which cost me £190.76 or 3p per kWh.

So there is no way you are using 48 pence worth of gas an hour all the time your heating is on. The thermostat will modulate the gas on and off.

Using your figures without any discount gives a kWh cost of .030552 per kWh based on 19,000 kWh of gas a year.

Your calculation is flawed.

molerat

flashnazia wrote: »

48p /hour doesn't sound ridiculous to me. I think it sounds right. 15p/hour sounds very low.

13 metric units per day = 146kWh. * 2.4p = £3.50 / 24 = 14.6p + .75p/hr st chg = 15.35p /hr

DemiDee

OK, maths was never my best subject. In fact, it was my worst. However, the calculations I have given here are not mine, but e.on's own calculations, based on my readings over five hours. For each hour except for one (for some strange reason), the meter moved up one digit. One digit apparently equals 11 units. One unit (until I get to the threshold to go onto the lower rate - again, all from e.on) is 5.34 pence.

Also, I have the heating turned to the lowest level, but the water is turned to the highest. Not sure whether that will make a difference. Water has to be turned to highest otherwise it's luke warm.

frankenstein

So, if your bill is set to 30 November, for example, then the payments on your higher rate begin on that date and continue until you reach the lower rate.

That may be how they see it but if you want to calculate what 1 kWh of gas is for the purpose of working out how much it is costing you when you use 100 kWh of gas in a day, Robert2009's explanation is pretty much spot on.

That is how I calculate the cost of my gas and electricity usage.

Gas for instance, using my figures

in a quarter if you use 7000 kWh of gas you are charged for approx 2680/4 = 670 kWh at .065247p per kWh = £43.60 and the remainder, 6330 at 0.031584 = £199.98.

Total £243.58 for 7000 kWh of gas.

So what does 1 kWh of gas cost?

£243.58/7000 = 3.5p

However in the summer if you never use more than 670 kWh in the quarter you will be charged 0.065247p per kWh where the e.on rep is correct.

670 kWh in 90 days is 7.5 kWh per day so if you use less than that a day the e.on rep is correct.

If you use 17.5 kWh a day it will cost 48p (7.5*.065247) plus 10 times 0.031548 = 31p which = 79p for 17.5 kWh = 4.5p per kWh

However if you use 107.5 kWh in a day it will cost 48p (7.5*.065247) plus 100 times 0.031548 = £3.10 = £3.58 for 107.5 kWh which becomes 3.3p per kWh.

neilmcl

aelitaman wrote: »

This is an interesting comment on the small radiator not getting hot when all the others are turned off.

The explanation for this could be that how a central heating system is designed is to have a thick 22mm ring of copper pipe that the radiators are dropped off using 15mm. The boiler works by sensing the return temp of the water in the thick ring and when it is returning at a set temp (hot) the boiler will switch off the burner and stop heating the water. So if because all the radiators are turned off bar one it means that the returning water temp gets up to the required temp quickly then not enough hot water has flowed to the small radiator, hence not enough heat disipated in the room to warm it up.

So the solution is to turn on more radiators so that the water takes longer to hit the temperature that the boiler stops heating the water so that more hot water flows through the small radiator so warming the room sufficently.

Or get your rads balanced correctly.

DemiDee

I just wish I had the brain of either Rob or Frankenstein - I'd be able to work out whether the electric heater or the central heating is more cost effective, as compared over, say, five hours. As it stands, I am more confused than ever! The explanations look good and I am sure that they are accurate, but a brain like mine sees figures and runs a mile, and thus ends up more confused - especially when calculations are involved. I guess I'm just going to have to wait for the big bill and see! Thank you all for trying to help! I am printing off your helpful posts and will see how far into the new year it takes before I can work it all out!

aelitaman

neilmcl wrote: »

Or get your rads balanced correctly.

The OP stated that when she turned every radiator off apart from the one in the room she was in, then that radiator only ever got warm not hot enough to heat the room.

Nothing to do with balancing.

DemiDee

You are right Aelitaman. In fact, it's not even the case that it doesn't get as warm as the others - just that it's a small radiator and thus heating the whole house makes it warmer in the office (incidentally the coldest room in the house, with the smallest rad).