Slow cooker - not as energy efficient as I thought

Gerry1

I wouldn't risk using a separate timer.

A slow cooker will be designed to maintain a certain temperature, and if you tinker with its power supply it can't do that.

In general, meats should be kept at freezer / fridge temperature or piping hot; a lukewarm temperature or one that's alternately blowing hot and cold might allow bugs and botulism to breed, so best not to take the risk, especially during a pandemic !

coffeehound

No the old SCs are very simple and crude: just two fixed heating elements and no thermostat.  In the long-running SC thread, a number of posters have said their newer ones ran hotter than their older ones and were judged to be too hot.  A timer would work fine on the simple SCs to reduce overall energy input over the course of a day-long cook.

matelodave

Probably OK on an old one but not much good on one with an electronic thermostat though. I agree with Gerry, you need to at least get it up to temperature and maintain all the food at an appropriated temperature to cook it and kill nasties rather than incubating them.

Thermostats have a much finer control of temperature and would be switching on and off at least every few minutes rather than in 15 minute cycles where the food would cool significantly between on periods. Although the duty cycle might be the same - say 50/50 it's not going to give the same effect as on for say 30 secs and off for 30 secs

macman

Slow cookers may be handy if you want to put a meal on in the morning and have it ready in the evening, but they are not going to save you any energy, nor do they vary in energy efficiency. They're all 100% efficient, being electric, and if some are less well insulated than others, then that energy is not lost, as it's heating the kitchen, at least during the heating season.
As to consumption, it take a fixed x kWH of energy to cook a meal, and x remains the same value, whether it's delivered at a rate of 200W over 14 hours, or 2,800W over an hour in a conventional oven.

tim_p

macman said:

<snip>
As to consumption, it take a fixed x kWH of energy to cook a meal, and x remains the same value, whether it's delivered at a rate of 200W over 14 hours, or 2,800W over an hour in a conventional oven.

Not quite. The slow cooker without a thermostat will take 2800 watts over 14 hours, whereas a conventional oven will switch on and off with the stat and probably use a lot less in the hour it’s on. Ours is rated at 2.2kW and uses nothing like that during an hours cooking. Sorry, just being pedantic. 

Gerry1

tim_p said:

macman said:

<snip>
As to consumption, it take a fixed x kWH of energy to cook a meal, and x remains the same value, whether it's delivered at a rate of 200W over 14 hours, or 2,800W over an hour in a conventional oven.

Not quite. The slow cooker without a thermostat will take 2800 watts over 14 hours

Not quite.  The slow cooker without a thermostat will take 2800 watt hours (2.8kWh) over 14 hours.

rp1974

macman said:

As to consumption, it take a fixed x kWH of energy to cook a meal, and x remains the same value, whether it's delivered at a rate of 200W over 14 hours, or 2,800W over an hour in a conventional oven.

Have you read or posted in this thread macman,by anychance:https://forums.moneysavingexpert.com/discussion/2148437/anyone-used-rointe-heaters/p1 .
Your post here reminded me of the conversations with Cristos,where he's proven the laws of physics,Albert Einstein,and basically the entire scientific community mistaken.

coffeehound

matelodave said:

Probably OK on an old one but not much good on one with an electronic thermostat though. I agree with Gerry, you need to at least get it up to temperature and maintain all the food at an appropriated temperature to cook it and kill nasties rather than incubating them.

Thermostats have a much finer control of temperature and would be switching on and off at least every few minutes rather than in 15 minute cycles where the food would cool significantly between on periods. Although the duty cycle might be the same - say 50/50 it's not going to give the same effect as on for say 30 secs and off for 30 secs

Yes definitely only the 'dumb' variety.  I realise that the warnings you and Gerry1 make are necessary, but I really think a 15-minute off period would be okay with an over-powered SC.  Some bubble furiously and lead to tough, overcooked meat.  The fact that they are on for so long gives plenty of time to exceed 72 degrees or whatever the safe temperature is.  Compare with fancy 'sous vide' methods where the meat never gets above 65.

rp1974 said:

Your post here reminded me of the conversations with Cristos,where he's proven the laws of physics,Albert Einstein,and basically the entire scientific community mistaken.

I particularly liked the post where he told a Chartered Engineer "I think you need to go back to school my friend"   

friendsrgreat

matelodave said:

Have you done a similar meter reading overnight without turning the slow cooker on.

 Unless you know what your base load is (stuff like the fridge, freezer, router, TV, DVD player, SKY box and even the central heating - it's got a pump, possibly a control board and a fan) you cant just do a meter reading and think its the slow cooker.

As Molerat says, 170w for 14 hours =2.38kwh and even then it's likely that the thermostat controlled the temperature so it wouldn't be using 170watts continuously. If you really want to find out how much it uses then you need one of these - https://www.amazon.co.uk/Xpork-Monitor-Consumption-Analyzer-Calculating/dp/B08K7G4XCH/ref=asc_df_B08K7G4XCH/?tag=googshopuk-21&linkCode=df0&hvadid=463215415376&hvpos=&hvnetw=g&hvrand=15729696617964760675&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=1006699&hvtargid=pla-1059153316306&psc=1 as it will just measure the consumption of what ever is plugged into it, like the slow cooker and not everything else that you've forgotten about.

I took another meter reading this morning when the slow cooker hadn't been on. I'd used 4 KWh overnight, despite what I thought was only the fridge-freezer being on. I went round my flat and found there was a heater in the bathroom that was switched on, despite my landlord telling me it wasn't(!). I have now turned this down as low as it will go and I'll see how this affects my energy consumption. At least I now know what the real issue is and I can likely keep my slow cooker.

Thanks for all your replies. I do appreciate them.

macman

coffeehound said:

matelodave said:

Probably OK on an old one but not much good on one with an electronic thermostat though. I agree with Gerry, you need to at least get it up to temperature and maintain all the food at an appropriated temperature to cook it and kill nasties rather than incubating them.

Thermostats have a much finer control of temperature and would be switching on and off at least every few minutes rather than in 15 minute cycles where the food would cool significantly between on periods. Although the duty cycle might be the same - say 50/50 it's not going to give the same effect as on for say 30 secs and off for 30 secs

Yes definitely only the 'dumb' variety.  I realise that the warnings you and Gerry1 make are necessary, but I really think a 15-minute off period would be okay with an over-powered SC.  Some bubble furiously and lead to tough, overcooked meat.  The fact that they are on for so long gives plenty of time to exceed 72 degrees or whatever the safe temperature is.  Compare with fancy 'sous vide' methods where the meat never gets above 65.

rp1974 said:

Your post here reminded me of the conversations with Cristos,where he's proven the laws of physics,Albert Einstein,and basically the entire scientific community mistaken.

I particularly liked the post where he told a Chartered Engineer "I think you need to go back to school my friend"   

Einstein? Pah! I have no time for him at all. To the best of my knowledge, he didn't even have a slow cooker, so his theories must therefore be completely without foundation.