Crockpots/Slow Cookers - Energy Efficient?

**NcsstyBrdsIngnty** · 01-06-2010, 11:31 AM

Hmm, I don't see a breakdown above so I will provide mine - please let me know if anyone finds flaws in it?

I have a cheapy Walmart 5 qt slow cooker and a cheapy electric oven that came with the house. I show .200 kWh average for the slow cooker and 2.9 kWh to run electric oven (estimate from online, saw anywhere from 2900watts to 7500watts estimated for ovens).

700kWh costs me $56.09 (cheapest in state!) according to my electric company.

.2 x 8hours of slow cooker = 1.6kWtotal
2.9 x2 hours of oven (essentially it's "on" for four hours, but is turning off and on so is really only running 1/4 of the time, but everytime it turns it's heating element on, it has a hard start and a spike in energy usage, and that in turn adds to the electricity usage so I decided on 2 hours of usage)= 5.8kWtotal

each kWh costs me .08012857( give or take

)

so the slow cooker costs me 12.82cents for 8 hours
and the oven costs me 47.15cents for 2 hours.

Even if my oven was super duper efficient and only ran (including energy spikes for hard starts) for 1/4 of the time the meal was in there, or one hour of electricity usage - I would still have used 23.575cents vs 12.82cents for my slowcooker.

I am sure this is very different for gas users. Also, I refuse to counter in that the furnace might not have to turn on for one or two cycles, as too many variables can be listed to counter this - including house insulation values, window uvalues, efficiency of furnace/heatpump/boiler/etc and ductwork/piping if applicable, source of energy for heating unit, etc. It may be that the energy given off from the oven may trick the TSTAT, but it doesn't actually skip a cycle as the next time the heating unit kicks on it has to run longer. . .too many variables to calculate all of that.

**Grainlady** · 01-06-2010, 12:06 PM

Another method that will save energy is using a pressure cooker. A method more people might like to try, especially in the summer to keep the heat out of the kitchen is "cooking" in a Thermos. I "cook" beans, grains, oatmeal, and pasta in a Thermos using hot water I heat in an electric kettle.

**2ndGenGranola** · 01-06-2010, 12:34 PM

Originally Posted by NcsstyBrdsIngnty

Hmm, I don't see a breakdown above so I will provide mine - please let me know if anyone finds flaws in it?
.

IMO the flaw with the mathematical approach is that the figures on the appliance are not that accurate. They are like the stickers on the car windows giving the beautiful gas mileage figures. When I started tracking by daily meter reading and then the Kill-a-watt, it became obvious where the true power pulls were.

**NcsstyBrdsIngnty** · 01-06-2010, 01:06 PM

Originally Posted by 2ndGenGranola

IMO the flaw with the mathematical approach is that the figures on the appliance are not that accurate. They are like the stickers on the car windows giving the beautiful gas mileage figures. When I started tracking by daily meter reading and then the Kill-a-watt, it became obvious where the true power pulls were.

Just my opinion, but I think the UL listing is very accurate (and ANSI approved), so I am just going to have to disagree. The manufacturing companies pay a lot of money to have an independent, trusted source (Universal Labs) test these products to prove safety and what their labels indicate, and I side with them. Yes, breakdowns happen in appliances as they become older and less efficient, and I think that is what you are indicating. I can appreciate your commisioning of the products in your home, it is so much more than most people do! But in my opinion that isn't going to change the difference without significant breakdown on the slow cooker and an extreme efficiency on the part of the oven. In that case, I think it would be wise to calculate the Payback time on a new slow cooker!

**frugalfranny** · 01-06-2010, 01:36 PM

Nothing to add ......but some interesting reading.

Thanks for asking the question Libby.......

**2ndGenGranola** · 01-06-2010, 02:08 PM

Originally Posted by NcsstyBrdsIngnty

Yes, breakdowns happen in appliances as they become older and less efficient, and I think that is what you are indicating.

No that is not at all what I am indicating. One appliance was new, fresh out of the box. The others were about 1 year old, 3 years old, 10 years old and 20 years old. The 20 y/o was performing in a similar manner to the new one (and all those in between).

**NcsstyBrdsIngnty** · 01-06-2010, 03:12 PM

Originally Posted by 2ndGenGranola

No that is not at all what I am indicating. One appliance was new, fresh out of the box. The others were about 1 year old, 3 years old, 10 years old and 20 years old. The 20 y/o was performing in a similar manner to the new one (and all those in between).

I read a little bit more about your Kill-A-Watt. A couple things I am wondering about are:

1) is the 2% difference the Kill-A-Watt claims on max load it can calculate (like 2% of 1750watts, or 35watt difference allowable no matter what item it is plugged into) or is it 2% difference on each single item (.2kW, or a .004kW difference)? I saw this question in the comments of the review of the Kill-A-Watt. Very valid question.

2) Not that I know a great deal about this, but what is the likelihood you have, and aren't calculating, a power factor difference? As in, the slow cooker is only using .2kWh as the UL listing indicates, but has a .8pf so is really pulling .25kwh from the outlet, which you are seeing on the kill-a-watt?

3) do you calibrate this kill-a-meter? Or do you just use it in comparison to other appliances to see who is the biggest zombie/budget killer?

Very interesting stuff here. . .Thanks for sharing with me 2ndGen!

**lisaflex** · 01-06-2010, 06:15 PM

interesting info on this thread

i just like the ease of mine! and it has GOT to be cheaper than slow roasting in a dutch oven at 300 degrees for 5 hrs!

nothing better on a cold winter day then to come home at 2pm to a wonderful smelling house! wether it be pork or beef, etc...just smells good! and, best of all, dinner is just about done and good to go!

**Nada.Leona** · 01-07-2010, 05:54 AM

I swear, if it weren't for the crockpots (I have two, and intend to get another when I find the right price) poor DH and I would be living off PB&J. He can't (re: won't) cook and I work an opposite schedule to him. Between our crockpots and our countertop grill, we would gladly pay the higher wattage price rather than eat takeout or be up til midnight cooking (as it is, supper is usually had at 9pm or later).

**ladykemma2** · 01-07-2010, 07:31 AM

well, for me, the savings come from having dinner when i get home from work and not ending up in a restaurant on the way home, a pre-emptive strike for frugality!

**NcsstyBrdsIngnty** · 01-07-2010, 04:06 PM

Originally Posted by NcsstyBrdsIngnty

2) Not that I know a great deal about this, but what is the likelihood you have, and aren't calculating, a power factor difference? As in, the slow cooker is only using .2kWh as the UL listing indicates, but has a .8pf so is really pulling .25kwh from the outlet, which you are seeing on the kill-a-watt?

I just wanted to follow up with this as I have new information.

I spoke with an engineer here at work during lunch about power factors. He said to be careful because power factors are typically associated with motors, so a slow cooker wouldn't be a great example of this! My apologies for posting somewhat misleading information.

He also pointed out that "Ul Tested" is very different than a UL listing and this also could also be a source of frustration.

Just a thought anyway!