how to work out gas consumption?

spinningsheep

Just purely from an interest point of view, I put the boiler on constant today and it's just kicking in and out to maintain the thermostat temp in the hallway of 17.5 degrees which gives a temp of 21 in the lounge. I read the meter at 11.30am it was 3984.When the boiler kicked in at 12.45 I put it on an flow temp of 70 degrees and when it clicked off again at 12.15 approx I read the meter again and it was 3985. My approx calculation (v rough) is £1.50 for that 30 mins which seems very high? 28kw boiler. The biggest gas hob was also on for about 6 mins to heat some soup.

molerat

Is your meter metric or imperial ? 1 metric unit = app 11.3 kWh, 1 imperial unit = app 32.1 kWh (for a cv of 40.0)

spinningsheep

imperial Molerat, and on BG Websaver 11 plan

molerat

I have just worked mine out and it is 5kWh / 16p per hour so there is something wrong somewhere.

What were the 1/10th readings at. If you did not take them into account that would make quite a difference to your calculation.

edit ..... 28kW boiler, 80% efficient could use that in 1.25 hrs running flat out so if heating the house from stone cold then possible.

spinningsheep

Cheers Molerat this is what I thought. Must be my readings that are wrong as when I put in my readings from the 3rd to 17th Jan it says we have used £52 of gas which is about right for this time of year I would think?

spinningsheep

Just an update, turned the boiler temp to 60 instead of 70, no difference in the temp in the house, but when it fired up again some 2 hours later I checked the meter and it hadn't used even half a unit after 30 mins, so obviously way more economical.

espresso

spinningsheep wrote: »

Just an update, turned the boiler temp to 60 instead of 70, no difference in the temp in the house, but when it fired up again some 2 hours later I checked the meter and it hadn't used even half a unit after 30 mins, so obviously way more economical.

No not way more economical - the house was already up to temperature! If the boilers stat is set lower, it will simply take longer for the house to get up to temperature from cold.

spinningsheep

No espresso the house was "up to temp" before hand, heating has been on all day, so boiler just needs to top up the heat and when it did this the first time on 70 it used more gas than on 60 yet I felt no detrimental effect on the temp in the house

macman

Wrong: it takes the same amount of energy to raise the temp from a to b regardless of the boiler stat setting (all other conditions being the same, the primary one being the ambient temperature). At 60 it will take longer than at 70, because the water in the CH circuit is cooler. The cost will be the same.
It's like asking if it's more economic to switch on 2 bars on your electric fire or one to get the room to a certain temp. One will be slower, but not more economic, two will cost more per hour, but do the job faster-so the cost is once again the same.

espresso

spinningsheep wrote: »

No espresso the house was "up to temp" before hand, heating has been on all day, so boiler just needs to top up the heat and when it did this the first time on 70 it used more gas than on 60 yet I felt no detrimental effect on the temp in the house

Your test this morning was flawed because you did not read the meter accurately.

All that you have done this afternoon, is reduce the boilers flow temp and state that it's "way more economical"!

If you set your boilers temperature to it's lowest setting tonight, do you believe that it will use less much gas to get the house up to the same programmed temperature tomorrow than it did today, assuming that we have similar negative temperatures throughout the night?

Most gas will be used to heat the house up to the desired temperature and once there, keeping it at that temperature will obviously use much less depending on your properties insulation/heat losses etc. regardless of the boilers flow temperature.