Efficiency of Oil fired Aga Range

Chipboard

Woke up this am to find the Aga off - checked tank and its empty which confirms what I suspected, that we are using over 15 litres per day of keroscene. We only bought the house a few months ago and the guy who serviced the Aga says that they use about 4.5 or 5 litres per day. We only use our heating for 2.5 hours per day which I think is very limited use and I have recently had the boiler serviced and its efficiency checked and its working fine so the Aga must be drinking the keroscene. The Aga guy reckons that if you use the Aga to its full extent i.e. for cooking, boiling the kettle, drying clothes etc, that the cost is reasonable (taking into account what you save on the electric cooker, dryer, kettle etc). We are beginning to think that these arguments are rubbish and that Aga's are an expensive luxury which we can't afford.

Even if we believed that the Aga is using only 4.5 litres per day. The cost for two months is €262 (60 X 4.5 X 97c per litre). Our last 2 month Electricity bill had usage of 10.68 Kw per day and came to €144. If we scrapped the Aga and used say an additional 10 Kw per day our Electric bill would increase to €251 (+ €107) when standing charges are taken into account. This would be a saving of €155 every 2 months.

If, as I suspect, the Aga is using closer to 8 litres per day, and therefore costing €465 every 2 months, the saving by switching to electricity for hot water and cooking (at the same 10 Kw per day additional electric usage) is €358.

On top of all that its difficult to re-light the Aga so you generally have to get the service guy out - cost €90, and it has to be serviced atleast once a year at around €130 (and probably more often as they are tempermental machines).

Are they not the most inefficient appliance you could install in any home?

Billy Bunting

What AGA are we talking about ? Model.

Chipboard

Two oven model.

John T Carroll

Chipboard wrote: »

Woke up this am to find the Aga off - checked tank and its empty which confirms what I suspected, that we are using over 15 litres per day of keroscene. We only bought the house a few months ago and the guy who serviced the Aga says that they use about 4.5 or 5 litres per day. We only use our heating for 2.5 hours per day which I think is very limited use and I have recently had the boiler serviced and its efficiency checked and its working fine so the Aga must be drinking the keroscene. The Aga guy reckons that if you use the Aga to its full extent i.e. for cooking, boiling the kettle, drying clothes etc, that the cost is reasonable (taking into account what you save on the electric cooker, dryer, kettle etc). We are beginning to think that these arguments are rubbish and that Aga's are an expensive luxury which we can't afford.

Even if we believed that the Aga is using only 4.5 litres per day. The cost for two months is €262 (60 X 4.5 X 97c per litre). Our last 2 month Electricity bill had usage of 10.68 Kw per day and came to €144. If we scrapped the Aga and used say an additional 10 Kw per day our Electric bill would increase to €251 (+ €107) when standing charges are taken into account. This would be a saving of €155 every 2 months.

If, as I suspect, the Aga is using closer to 8 litres per day, and therefore costing €465 every 2 months, the saving by switching to electricity for hot water and cooking (at the same 10 Kw per day additional electric usage) is €358.

On top of all that its difficult to re-light the Aga so you generally have to get the service guy out - cost €90, and it has to be serviced atleast once a year at around €130 (and probably more often as they are tempermental machines).

Are they not the most inefficient appliance you could install in any home?

Non condensing Oil fired Boiler heating consumption (mine) is approx 7 Litres/Day, 7 X 10.45, or 73 Kwh/10 hour Day. The figure I have seen for cooking + kettle + toaster etc is 1.56 Kwh/person per day. If you are only turning on the heat for 2.5 hrs/day then assuming that the Aga and the oil fired boiler have the same efficiency of say 80% then you'r heating consumption would be approx 7 X 2.5/10 or say 1.75 Ltr/Day, Cooking+kettle etc should be 1.56/80% or 1.95 Kwh/person/day or 1.95/10.45, 0.19 Ltrs/person/day (kerosene).
For "2 person" family total consumption should be 1.75+(2X0.19), 2.13 Ltrs/day. "3 person" family 1.75+(3X0.19), 2.32 Ltrs/Day....."4 person" 2.51 Ltrs/Day..."5 person" 2.7 Ltrs/Day etc etc.
The Radiant Heat from the cooker must also be taken into account and the time the stove is "Lit". Assuming 10 hrs/day and a radiant heat of 2 kwh/hour, then the "radiant heat" consumption is 10X2/80%, 25 Kwh/Day or 25/10.45, 2.4 Ltrs/Day.
So Total Consumptions for "2 person2 is 2.13+2.4, 4.53 Ltrs/Day "3 person" is 2.32+2.4, 4.72 Ltrs/Day. "4 person" is 2.51+2.4, 4.91 Ltrs/Day.
The Radiant Heat has a very big effect on the fuel consumption, one would expect the Aga to have a pretty low radiant effect, can you get the exact model number off the cooker?, one can then do a more accurate sum. JTC

Chipboard

It's an OCB135. There's four in the house but two are small kids. House is c3000 sq ft. Our boiler is a condenser boiler and runs at 92 or 93%.

Thanks for your help.

John T Carroll

Chipboard wrote: »

Woke up this am to find the Aga off - checked tank and its empty which confirms what I suspected, that we are using over 15 litres per day of keroscene. We only bought the house a few months ago and the guy who serviced the Aga says that they use about 4.5 or 5 litres per day. We only use our heating for 2.5 hours per day which I think is very limited use and I have recently had the boiler serviced and its efficiency checked and its working fine so the Aga must be drinking the keroscene. The Aga guy reckons that if you use the Aga to its full extent i.e. for cooking, boiling the kettle, drying clothes etc, that the cost is reasonable (taking into account what you save on the electric cooker, dryer, kettle etc). We are beginning to think that these arguments are rubbish and that Aga's are an expensive luxury which we can't afford.

Even if we believed that the Aga is using only 4.5 litres per day. The cost for two months is €262 (60 X 4.5 X 97c per litre). Our last 2 month Electricity bill had usage of 10.68 Kw per day and came to €144. If we scrapped the Aga and used say an additional 10 Kw per day our Electric bill would increase to €251 (+ €107) when standing charges are taken into account. This would be a saving of €155 every 2 months.

If, as I suspect, the Aga is using closer to 8 litres per day, and therefore costing €465 every 2 months, the saving by switching to electricity for hot water and cooking (at the same 10 Kw per day additional electric usage) is €358.

On top of all that its difficult to re-light the Aga so you generally have to get the service guy out - cost €90, and it has to be serviced atleast once a year at around €130 (and probably more often as they are tempermental machines).

Are they not the most inefficient appliance you could install in any home?

Thanks for the info.... I mistakenly thought that the AGA supplied your heating as well.

If one googles AGA OCB 135 it states that the “Idling” Oil consumption is 6 cc/min equals 6X60/1000, 0.36 Ltrs/hr. The “Cooking” Oilconsumption is 8cc/min equals 8X60/1000, 0.48Ltrs/hr. You can now figure out your AGA Oil consumption easily enough, for example if you have it on for 24hrs/day with the setting on “idling” (Low Fire) for 18 hrs/day and on “Cooking”(High Fire) for 6 hrs/day then the (AGA) oil consumption is 18X0.36 + 6X0.48 or 9.36 Ltrs/day, if you run it for 12 hrs/day, say 6 hrs at Low fire and 6 hrs at High fire then the (Aga) oil consumption is 6X0.36 + 6X0.48 or 5.04 Ltrs/day. The AGA “manual” states that the approx weekly oil consumption is 65.15 Ltrs/week or 9.31 Ltrs/day.

The AGA OCB 135 has a 2 KW Boiler, if one assumes that its output is 1.0 KW/hr for 12 hrs and is used only to heat water via an indirect coil in the Hot water Cylinder and assuming 1 Kwh/day cylinder losses then the useful hot water produced should be (1.0X12)-1, 11.0 Kwh/day, enough to heat 189 Ltrs of water from 10C to 60C, calculation is 11.0*860/(60-10).

If you decide to “throw out” the Aga then the sums might look something like this.

Cooking requirement, 4*1.56, 6.24 Kwh/day. Hot Water requirement based on above usage of 189 Ltrs/day, [189X(60-10)/860]+1, 12.0 Kwh/day.

Assuming Electric Cooker+Elect.Kettle+Toaster is used for the Cooking and elect cost of E0.23/Kwh then “cooking” cost is 6.24X0.23,E1.44/day. The hot water requirement will have a huge effect on your bill depending on the energy source, if all electric immersion heating is used, cost is 12.0X0.23, E2.76/day. Total 1.44+2.76, E4.2/day. If all the hot water is generated by a coil (which may be already fitted) fed from the Central HeatingBoiler (@90% effic) then hot water cost is 12/0.9/10.45X0.95, E1.21/day. Total 1.44+1.21, E2.65/day. (Assumes Kerosene @ E0.95/Ltr). Note, if the Central Heating Boiler is only run for 2.5 hrs/day then this will not give 12 Kwh heating and may need “zoning” to allow the boiler to feed the coil only,sometimes. If the hot water energy requirement is provided 50/50 by Electric Immersion/Boiler coil then hot water cost is (6X0.23)+(6/0.9/10.45X0.95), E1.99.Total,1.44+1.99, E3.43/day.

The AGA “manual” states that the approx weekly oil consumption is 65.15 Ltrs/week or 9.31 Ltrs/day. If this is accepted then the running cost is 9.31X0.95,E8.85/day.

It would be interesting to see many hours/day extra that the Central Heating Boiler would have to be run to compensate for the loss of radiant heat (if any) from the AGA should it be switched off.

If you dont mind you might state how many hours/day the AGA is running and (roughly) the time spent on High fire.

Apoligies for the long windedness of this reply but at least it gives some food for thought. JTC

Chipboard

Your figures confirm what i've been thinking.

The range is on the same setting 24/7. The operating manual states that if you set the control knob to 4 it will settle at or around the correct working temperature as shown by a black vertical line a little more than half way across the heat indicator. You then tweak the setting a little either way to get it to settle on the black line and it stays at that temperature. The manual states that if the indicator is in the black the heat is too low and if its in the red it's too high.

It's likely that this monstrosity of a thing was guzzling 11 or 12 litres and costing c€10 and change per day. It's a pity it's not fed from a seperate tank to the boiler as it would have been obvious from the start how much it was costing to run.

We thought when we bought the house that we would only turn it up to cook but this model definitely doesn't work that way. I've heard of someone turning down their aga and only turning it up to cook but you couldn't do that with ours as when you change the setting it takes around 24 hours to adjust to the new temperature. As I said above the manual clearly states that it is to be maintained at the operating temperature.

I'm trialing leaving the immersion on 24/7 to gauge how much that will cost. I'm sure it will be less than the Aga at any rate. All we got from the Aga was hot water (outside boiler heats house) and I'm pretty sure the immersion will take care of that for less than €10 per day! I have an Owl electricity consumption meter so will report back in a few days on that.

I'm going to look into installing a stove where the Aga is to supplement the immersion and throw a bit of heat into the kitchen (it's quite large and needs some heat during the day - the Aga heated it a bit but not that much as they are designed to retain heat). I realise that (unless Aga's are terribly inefficient) I won't get more hot water and more heat in the kitchen for less cost but the truth is that we had far too much hot water with the Aga so much so that it was dangerous to let the kids near the taps even though I had the thermostat turned to low (will get this checked also).

If we had 60% of that hot water we had previously, with a bit of heat in the kitchen for slightly less cost we'd be better off. I think no matter what we settle on it won't cost over €10 a day.

Chipboard

I tried three different strategies since I last posted.

I switched the Aga off on 16 December and switched the immersion on (set to Bath). The first day (24 hrs) it used 33 kw's which I figured would be less the second day but again it used exactly 33 kw's. At 18c a kw (including Vat) that's around €6 a day so while cheaper than the Aga it still wasn't very cheap (just for hot water) especially as the kitchen was that bit colder. It is a 300 litre cylinder though which is fairly big. Mind you there were no baths and probably only a couple of showers used in the 48 hours I had it on so I wonder how much it would have cost if it was the weekend and you had a bath night for the kids and a couple of showers each. It would have been interesting to leave the Aga off and monitor oil consumption to see how much it had been using but as Christmas was approaching I decided to re-light the Aga after only the two days. If it could talk I'd say it would have been muttering something smart assed as I re-lit it.....

When I re-lit it I only turned it up to around 2 1/4 instead of 4. I figured this would be enough to heat the hot water but not to cook. As it happens it was enough to do both albeit you had to leave food in a small bit longer. After two weeks of that I checked the oil usage again and it worked out at 13.2 litres per day (note that this consumption includes the boiler on for around 3.5 hrs per day so probably splits Aga 7.95L and boiler 5.25L per day) which is feck all better than with the Aga on normal heat setting (Aga 9.75L and boiler 5.25L total 15L).

The problem I had (or thought I had) is that if I switched off the Aga altogether I would have no hot water. Our outside boiler had only been heating the rads and not the water but it turns out that the thermostat on the cyclinder (which I mentioned I was going to have checked in an earlier post) had tripped out, due I think to the water overheating in the cylinder. It turns out that it is this thermostat which 'calls' the outside boiler for water when the cylinder cools. Now that it is reset I am getting heating and hot water from the outside boiler.

Now that I'm not tied to the Aga or the immersion, on Saturday just gone I switched off the Aga again but I increased the amount of time the boiler is operating to 8 hours a day. The boiler is heating the house and the cylinder and I am going to leave it like that for the week and check the usage per day again next Saturday. Even if it uses in or around what we were using before with both (boiler and Aga) operating it will be better as I have heat to the entire house most of the day rather than just the kitchen.

I'll post up the consumption this weekend. I realise that a milder or colder outside air temperature during the week will affect this but it probably won't be hugely different.

John T Carroll

The Immersion consumption of 33 Kwh is enough to heat 546 ltrs of water from 8C to 60C.This is an enormous amount of hot water, one would expect the consumption to be in the region of 125 to 200 ltrs/day or an Immersion consumption of 7.6 to 12 Kwh/day. If the consumption is indeed 33 Kwh then this would require about an extra 3.7 ltrs/day of Kero. If the Hot Water requirement is, say 10.0 Kwh then this would require about an extra 1.2 ltrs/day of Kero. Based on my Heating equirements which are around say 85 kwh/day input or 8 ltrs/10 hour day, then your heating requirements for an 8 hour day should be about 6.5 ltrs/day. Total, (6.5+3.7), 10.2 ltrs/day or (6.5+1.2), 7.7 ltrs/day. It would be well worth rechecking the Immersion Consumpton as this, when measured accurately, gives a very good idea of the hot water quantity, its very difficult to measure the amount of oil required. Even if the cylinder is losing 3 kwh/day the the Immersion is still producing 496 ltrs/day which still seems very high....JTC

aireng

Chipboard wrote: »

I tried three different strategies since I last posted.

I switched the Aga off on 16 December and switched the immersion on (set to Bath). The first day (24 hrs) it used 33 kw's which I figured would be less the second day but again it used exactly 33 kw's. At 18c a kw (including Vat) that's around €6 a day so while cheaper than the Aga it still wasn't very cheap (just for hot water) especially as the kitchen was that bit colder. It is a 300 litre cylinder though which is fairly big. Mind you there were no baths and probably only a couple of showers used in the 48 hours I had it on so I wonder how much it would have cost if it was the weekend and you had a bath night for the kids and a couple of showers each. It would have been interesting to leave the Aga off and monitor oil consumption to see how much it had been using but as Christmas was approaching I decided to re-light the Aga after only the two days. If it could talk I'd say it would have been muttering something smart assed as I re-lit it.....

When I re-lit it I only turned it up to around 2 1/4 instead of 4. I figured this would be enough to heat the hot water but not to cook. As it happens it was enough to do both albeit you had to leave food in a small bit longer. After two weeks of that I checked the oil usage again and it worked out at 13.2 litres per day (note that this consumption includes the boiler on for around 3.5 hrs per day so probably splits Aga 7.95L and boiler 5.25L per day) which is feck all better than with the Aga on normal heat setting (Aga 9.75L and boiler 5.25L total 15L).

The problem I had (or thought I had) is that if I switched off the Aga altogether I would have no hot water. Our outside boiler had only been heating the rads and not the water but it turns out that the thermostat on the cyclinder (which I mentioned I was going to have checked in an earlier post) had tripped out, due I think to the water overheating in the cylinder. It turns out that it is this thermostat which 'calls' the outside boiler for water when the cylinder cools. Now that it is reset I am getting heating and hot water from the outside boiler.

Now that I'm not tied to the Aga or the immersion, on Saturday just gone I switched off the Aga again but I increased the amount of time the boiler is operating to 8 hours a day. The boiler is heating the house and the cylinder and I am going to leave it like that for the week and check the usage per day again next Saturday. Even if it uses in or around what we were using before with both (boiler and Aga) operating it will be better as I have heat to the entire house most of the day rather than just the kitchen.

I'll post up the consumption this weekend. I realise that a milder or colder outside air temperature during the week will affect this but it probably won't be hugely different.

Hi,
what did you do with the AGA in the end? I've just moved into a house and have the same problem except that my outside boiler doesn't heat the water. I have a seperate tank for the AGA, I put €200 in at the beginning of last month and its neearly gone. AGA's are a luxury but having that much hot water is nice