question on gas consumption

[wobblymike]

we returned home yesterday 4 dec after a 16 day holiday. prior to departing i set the central heating thermostat to switch the heating on if the temperature dropped to fifteen degrees. we have a fairly new combi boiler which is fully electronic i.e. no pilot light. we also have a newish gas fire which has a pilot light which i forgot to switch off before we left. i read the meter prior to leaving and again when we arrived back yesterday - i was horrified to see we had used 14 units (imperial meter) approx 450kwh at approx 28kwh a day with only the pilot light on the fire consuming gas. i understand it was quite cold these last 2 weeks but i would be surprised if the temperature in the house got low enough (15 degrees) to kick the heating on although i suppose its possible, as an indicator,when we arrived home yesterday with an outside air temperature of 5 degrees and after i had read the meter i clicked the thermostat on; it switched the heating on at 19 degrees. i would be grateful for any thoughts as to this consumption before i investigate further.

[htg engineer]

I don't understand? the outside temperature is 5 degrees but you'd be surprised if inside dropped below 15, why?

If outside is 5 degrees and there's no heating on then the temperature inside will drop to well below 15 very quickly. Having the thermostat set to 15 degrees, the heating has probably been on more than it's been off which is not necessary. All you want in this weather is for the heating to come on to prevent freezing pipes, and if your boiler is that modern it probably has a frost stat built in.

You would have been better having the heating on timed to come on in the evening and early morning.

Setting the thermostat to 15 degrees means you want the house temperature at a constant 15 degrees or above, 24/7 and in this weather it will use a fair of gas.

htg