Daily gas consumption (when central heating off / in summer)

[divefoor]

We recently had some massive electricity bills in our new home and with some helpful input on this forum discovered the boiler was running with immersion heater switched on.

The electricity consumption dropped massively since switching it off. However, gas consumption has since rocketed and I’m concerned the boiler's gas consumption may be excessively high / faulty relative to our usage.


From some research I see daily gas use averages quoted anywhere between 30 to 55kw a day.

Home Gas Consumption
- Without central heating our house now seems to use 2.7164 m3 / 30kw a day.

That seemed pretty high to me (given heating is off).
I'm concerned there might be a fault and that’s why the immersion heater was left on.

- With heating on for 4 hours that rises to about 5.4m3 / 60kw a day.


Boiler System
Our system is a bit odd in that hot water is always ‘on’. There are two boilers that work together. An ideal Logic and Gledhill Boilermate 3

The Boilermate has a timer to control heating on/off but there seems to be no means to control hot water which is always available.


Does 30kw a day sound excessively high for a house running hot water but not heating?


Usage details
30kw average per day was measured over 10 day period:
- no central heating
- aprox 2 showers a day
- only 1 hot bath in that period
- no dishwasher used
- washing machine used once


Any advice appreciated

Thanks!

 

[sajeel]

30kw x 12p = £3.60 if your meter is metric not cubic that sounds about right depending on size of property

with regards to your hot water you need a 2 channel timer
something like this should do https://www.tlc-direct.co.uk/Produc...=finalurl_v2&gclid=CIe76L-P49ICFQq3GwodHfYJ2A

 

[ianniann]

Sounds a lot to me, for the usage you quote. 25p/shower (for gas boiler, heating only, not the cost of the water) is a good starting point, which would be 50p/day. You might have very long showers, there might be other hot water uses you haven't listed, you might have a very inefficient boiler, or the you might losing three quarters of the heat from your hot water before it ever gets to the shower.

Note that the Boilermate isn't really a boiler, just a thermal store to help with the hot water.

I'm confused as to just which question sajeel has answered ...

 

[JohnD]

30kw x 12p = £3.60 if your meter is metric not cubic

12p per kWh is about the price of energy from electricity, though a bit on the high side.

Energy from gas costs about 2.5p per kWh

So "metric not cubic" is not right

BTW my summer gas usage (hot water only, two adults, showers, kitchen sink etc, condensing boiler plus blue cylinder) was 21 cu.m last June, which is 235kWh for the month, which cost £4.95 plus standing charge plus VAT. About 7.8kWh per day in summer.

You mention daily gas averages of 30 to 55kWh.

That can only be the average for the whole year, including winter heating.

My whole-year usage is 1,280 cu.m which is about 14,210 kWh so average 39kWh/day. Almost all used in winter, when I use 5 to 8 cu.m a day depending on the weather.

I'm surprised you say your heating is off.

60kWh/day when the heating is on is quite low.

 

[divefoor]

Thanks for your feedback.

The meter units are measured in m3 which I converted to Kw.
Calculated the Kwh by:
gas units x calorific value (39.1) x volume correction 1.02264 ÷ 3.6


I can’t really think of any other hot water uses other than washing up.
The showers are not long ones. Not that I’m timing but I guess 5/10m

Any time hot water is used that seems to trigger the logic boiler to burn.

From my research I see Boilermate’s do not seem get a lot of love so perhaps it is not very efficient as a hot water tank.

I guess I’m just hoping to determine if it’s behaviour is characteristically inefficient or high to the degree that something may be faulty.

thanks again

 

[endecotp]

- Without central heating our house now seems to use 2.7164 m3 / 30kw a day.

Please learn the difference between kW (kilowatts) and kWh (kilowatt hours). What you've written is like saying "the distance from London to Edinburgh is 400 miles per hour".

15 kWh per shower is not totally impossible, e.g. if they are very long showers with a high flow rate, but it does seem unlikely.
Do you really not have any central heating on? It's March; how are you heating the house?

 

[flameport]

Seems excessive. Mine is about 50 cu ft / day (1.41 m3) with no central heating and that includes a small amount for a gas hob.
Peak usage in the winter with heating, hot water and gas hob is between 200-250 cu ft / day, or 5.6m3 - 7m3 per day.
3 bed detached house, 2 adults, 3 children + 1 baby, heating typically on 12 hours a day.

Gledhill Boilermate 3

How well insulated is that contraption?
Is there a wall of heat when you open the door to the cupboard where it is located?

A timer will be of no use with a thermal store - by design they must be kept hot all the time.
Personally I would be replacing it with an unvented cylinder at the first opportunity.

 

[JohnD]

The meter units are measured in m3 which I converted to Kw.
Calculated the Kwh by:
gas units x calorific value (39.1) x volume correction 1.02264 ÷ 3.6

You can calculate it "near enough" by saying 1 cubic metre contains 11.1kWh.
It's quicker and easier, and you can sensibility-check by eye.

If you want to do it in your head you can just multiply the cu.m on the meter by 10, which is a rough approximation, but often sufficient.

 

[divefoor]

Sorry for my confusion re units. And thanks for the tip re calculating.
So that should be 30 kWh

60kWh/day when the heating is on is quite low.

Agreed, but it was only on for four hours during the days I tested with the heating on

The heating has been off for a week while I monitored and logged the readings (and yes it has been pretty cold! but we have a fire place and electric radiator to fall back on)

Our hob uses a tiny proportion of gas maybe 0.1 or 0.2 on the gas meter

How well insulated is that contraption?
Is there a wall of heat when you open the door to the cupboard where it is located?

There's no insulation wrapped around the cylinder.
When opening the cupboard to the boilermate water tank you can feel the warmth it generates.

When the immersion heater was on it seemed to add about 9kwh to the daily electricity consumption which seemed massive.

But now that's off the boiler uses up about 30kwh to just supply hot water.

At 3p per Kwh for gas that doesn’t seem much more efficient than using the immersion heater which seems pretty wrong.

 

[rules&rulers]

Had a BM3 in a previous property,the hot water heat up is on permanently the boiler use to fire up for around 9 minutes every hour during the night/early morning during times of no hot water draw off,the boiler thermostat was set at maximum so making the flow and returns give off a lot of wasted heat under the floors very noticeable during the summer.
The shower has 4 body jets and a ceiling rose so a lot of water under mains pressure consumed, so more gas required to reheat the BM3.

Always noticed the airing cupboard was very hot,maybe the BM3 is not very well insulated under its metal exterior.

Dont know about the gas consumption as only lived there for a year,the utility company never billed us although a direct debit was set up,silly billys.

 

[endecotp]

I noted the comment above about the boiler coming on whenever hot water was used, and I've looked at the Boilermate instructions:

https://www.unventedcomponentseurop...3-III-installation-servicing-instructions.pdf

That confirms (on page 19) that the system is normally configured so that the boilermate can call for heat from the boiler at any time.

I haven't read the whole thing. Maybe there are settings that can he tweaked to provide some hysterisis.

 

[divefoor]

BTW my summer gas usage (hot water only, two adults, showers, kitchen sink etc, condensing boiler plus blue cylinder) was 21 cu.m last June, which is 235kWh for the month, which cost £4.95 plus standing charge plus VAT. About 7.8kWh per day in summer.

Wow I missed that the first time but that seems a big difference. i.e. much more efficient.
I'm wondering would adding insulation to the water tank make that much difference.

The way the boilermate is configured to call for heat at all times seems pretty significant too.
There is a honeywell timer fitted to the boilermate to control the heating but no control of the hot water through it.

Would it be in theory possible to add a control for the hot water with this system too? Something that would in effect replace the honeywell controller? (Sorry for the rooky questions)

And thanks again for all the feedback on this. much appreciated.

 

[endecotp]

How far away is the boiler?
Is all the pipework lagged?

 

[divefoor]

there is some lagging on the pipes around the water tank but not all.

boiler is on the ground floor and tank is on the 1st floor.

I guesstimate about 3 or 4m apart as not directly above

 

[endecotp]

it would be interesting to know by how much your gas consumption goes down if it is turned off during the night and daytime.