High gas usage

Optimistic_Gardener

BUFF said:

Optimistic_Gardener said:

We also have an unvented tank, which we had installed to improve the water pressure when we moved in. Is this the same as a pre-heat tank and Would it make a difference to turn this off - presuming that's possible?

Also, our boiler is an old Baxi combi, but reading other forums it seems the cost of replacing it wouldn't make that much difference to our bills? 

How is your unvented tank heated? (it would be unusual for a combi to do this)
How old is your Baxi (& model no. ideally) & what controls do you have throughout the house (programmer, room 'stat, TRVs)

Thanks. The boiler was here when we bought the house and there's a sticker saying it had a Sentinel X100 inhibitor in 2002 - so over 20 years. It's a Baxi Combi Instant 105e and yes we have TRV's on all rads and thermostat controls upstairs and down

BUFF

Baxi Combi Instant 105e is a non-condensing combi with an efficiency of just under 80% when new. Do you get it serviced annually & if so does the flue gas report give an efficiency figure?

A new condensing combi will be over 90% efficiency when new (if run correctly to max efficiencies) so you should see a reduction in gas usage but it will cost you several £thousands to buy & install. What is your annual gas usage kWh? With that & kWh price you can work out how many years that reduction will take to pay for the replacement.

Your combi should give you mains pressure hot water (12.7l/min at 35C rise)  so still strikes me as odd that you also have an unvented.

Optimistic_Gardener

BUFF said:

Optimistic_Gardener said:

We also have an unvented tank, which we had installed to improve the water pressure when we moved in. Is this the same as a pre-heat tank and Would it make a difference to turn this off - presuming that's possible?

Also, our boiler is an old Baxi combi, but reading other forums it seems the cost of replacing it wouldn't make that much difference to our bills? 

How is your unvented tank heated? (it would be unusual for a combi to do this)
How old is your Baxi (& model no. ideally) & what controls do you have throughout the house (programmer, room 'stat, TRVs)

The unvented tank is not heated by the combi. It only supplies hot water for the bathroom

BUFF

so how is it heated? If electricity I hope that it is on E7  or similar.

Optimistic_Gardener

BUFF said:

Baxi Combi Instant 105e is a non-condensing combi with an efficiency of just under 80% when new. Do you get it serviced annually & if so does the flue gas report give an efficiency figure?

A new condensing combi will be over 90% efficiency when new (if run correctly to max efficiencies) so you should see a reduction in gas usage but it will cost you several £thousands to buy & install. What is your annual gas usage kWh? With that & kWh price you can work out how many years that reduction will take to pay for the replacement.

Your combi should give you mains pressure hot water (12.7l/min at 35C rise)  so still strikes me as odd that you also have an unvented.

Yes, boiler serviced annually, but not sure about the efficiency figure, will check. Gas usage is high, despite doing all the efficiencies suggested to the OP already.
It's a large old house, with a hodge-podge of pipework, apparently bits bolted on over the years - before us - which I'm sure creates/adds to the inefficiencies. We only have one shower but water dribbled out, hence we were advised to replace the old copper cyclinder with the (secondhand) unvented tank. 
It seems like we just have to suck it up as we don't plan to stay long term... Thanks again