HW Gas consumption for empty house ?

[bwel]

Hi all,

Bit of an odd question here. I've been on holiday and have the CH switched off, but did not stop the twice daily boost of HW on the timer. Given that here is no HW been consumed in the house when we are away I expected the gas consumption to be minimal as the loss from the 2 x uniSTOR tanks would be minimal and thought the boiler would start and then see there was not heat demand because the water is already at or near temp.

Any ideas why the consumption is running at about 55p per day with no water usage ?

Of course next time I'll just switch off the HW timer, but my concern is that every year about £200 is the background HW cost before actual useful usage if HW is added.

Many thanks

 

[Harvest Fields]

Do you have a daily standing charge for your gas?

 

[bwel]

Do you have a daily standing charge for your gas?

Hi yes there is a standing charge, but there is actual Kw consumption in the graphs.

 

[Ric2013]

My 117l DHW cylinder uses about 10kWh gas to heat from cold. This is the gas consumption and includes the inefficiency of my old boiler.

I have, however, noticed that re-heating this cylinder from the previous day (even if no water is drawn) seems to entail a lot of cycling from my boiler and extensive run time of the pump. From this I can imagine significant heat losses through primary pipework and boiler running inefficiently at low heat demands since the stored water is virtually at the same temperature as the water running through the boiler.

And that's why I want a thermal store.

Your 50p could well be around 10kWh, so while this is a bit high, I'm not surprised, unless you have a condensing boiler. You may find that if your boiler temperature is a user setting and you plot gas consumption vs temperature on a graph, you will find the best setting for your system.

 

[Chuck]

loss from the 2 x uniSTOR tanks would be minimal...

Assuming the uniSTOR tanks are relatively new models the standing losses from the tanks alone will be, say, 1.5 kW hr per day each, i.e. 3 kW hr / day total. Could be a bit less or a bit more depending on model.

You've made the question imposible to answer by not giving figures in kW hr and not saying how much you are paying for gas, but if I guess at 3.3p / kW hr then the standing losses from the tanks will be ca 10p / day.

Did you check is the water meter reading before and after your vacation? If you left a hot tap not properly turned off, that might be the explanation. 6 kW hr is enough to heat ca 100 litre of hot water, so it would need to be dripping fairly frequently.

 

[Ric2013]

And what boiler do you have? We need to consider that the energy transfer from gas to hot water in the cylinder could be quite inefficient.