Nest thermostat increasing energy bill

sxp842

Hi all

hoping someone can give me some advice. We had been renovating our flat for a while and we got a new valliant combi boiler installed about a year ago. No thermostat was installed with it. We then eventually moved into our flat in September 2020. However, we only just got a nest thermostat installed 2 weeks ago. Prior to this we were just controlling the temperature on the boiler and radiators.

 Since we got our nest thermostat installed our smart meter is showing that our daily energy usage has almost doubled. In the month prior  to the thermostat we were spending approx £2 a day, but now it is approx £3.50-£4 per day. The flat is no warmer than it was before (if anything it is a bit colder).

I’m really confused as to why our bills are so much higher now since installing the thermostat? I understand there may be a bit of a difference but almost double seems extreme. Nothing about our lifestyle has changed (my partner and I have been working from home since Sept), and the weather has got better since the thermostat was installed - surely our bills should be going down if anything.

Currently our thermostat is set to 21 during the day and 18 at night. We are two people living in a 2 bed flat.

Does anyone have ideas on what could be the cause? 

A family member who is an electrician installed the thermostat. Could it be something to do with the way it was installed? Or more like that we are not using it properly?

thanks

sxp842

Also correction to the above - it’s a viessmann combi boiler, not valliant

Robin9

Have you set all the on / off times and target temperatures within Nest ?     

theoretica

Previously, were you turning the boiler off overnight? Why is the Nest set so high overnight?  Have you got radiators in rooms you aren't in turned up when before they were turned down?  Is the boiler firing up more often?

Perception of warmth varies interestingly from how warm it actually is - you may find your current system averages to a higher temperature without feeling warmer.

tim_p

If you’ve just let the Nest learn by itself then I’m not at all surprised. I fitted my Nest a few years ago now but knew within days it was using a lot more gas than the standard ‘stat it replaced. Turned off all the bells and whistles, set up a working schedule (far more control than previous controller) and then started to save a small amount. I love my Nest and wouldn’t swap it for anything (right now) but never bought in to all the ‘make big savings’ BS. Love being able to control remotely and coming home to a warm house when returning from holidays (remember them?) etc. 

cattom

all the stat does is turns the heating on and off, instead of you doing it manually. its what you've got it set to, and how you programmed it that matters. 

Hasbeen

Was going to suggest that as well.  LOL

Electrician would have set it up to come on and off at certain times for each seperate day.

Also different temperatures each day at given times.

Log onto your online Nest account and change to suit your lifestyle.

Mrs_Arcanum

Also worth accounting for the very cold snaps over the last couple of months.

sxp842

Thanks all, we have switched off the self-learning function and have set a schedule instead. I’ll try turning down the night time temp and see if that makes a difference

Previously we didn’t switch the boiler off overnight and we used to have the radiators turned up in rooms we weren’t using, whereas now we don’t - but the usage is still higher than before (even during the cold snap)

I’ll try and play about more with the schedule settings and see if that makes a difference 

FreeBear

Got any TRVs on the radiator nearest the thermostat ?

If so, the TRV could be shutting the radiator off before the room is up to the temperature the thermostat is expecting.

tim_p

sxp842 said:

Thanks all, we have switched off the self-learning function and have set a schedule instead. I’ll try turning down the night time temp and see if that makes a difference

Previously we didn’t switch the boiler off overnight and we used to have the radiators turned up in rooms we weren’t using, whereas now we don’t - but the usage is still higher than before (even during the cold snap)

I’ll try and play about more with the schedule settings and see if that makes a difference 

I’ve got the scheduling down to a fine art now, only gripe is the restriction of an hour and only in 15 min slots.