This morning, after the main morning news, invited cooks were on Global TV. The twist was these women specialized in preparation of food in slow cookers. They mentioned one benefit of this method of food preparation was energy efficiency. I thought that was odd as I always believed the devices, plugged in for hours, might have benefits but certainly not electricity savings. So, I went to the Internet.
There is a major flaw in the logic of nearly half of the sites I found. Of course, when compared to an electric oven, a crock pot uses many fewer watts. I kept seeing the phrase, equivalent to a light bulb, when discussing 100 to 250 watts. (Modern LED light bulbs use only about 8 watts, but that is another story.)
So, if a dish has to be cooked for one hour in an oven, a slow cooker might appear to use less electricity even though it takes eight times longer. However, those sites neglected to calculate that when an oven cooks for one hour, it is only using full power to heat up. Once it has reached temperature that little light goes off. So, efficiency has a lot to do with the oven's insulation. Oh, and stop opening the door to peek inside! On the other hand, a slow cooker is running at the temperature chosen for the full cooking time.
Dozens of other factors come into play. For example, a crock pot may include all the components of a meal; whereas, not everyone makes use of an oven for the complete lunch or dinner. Choosing to buy or use a slow cooker for energy efficiency probably depends a lot on what and how often one cooks. I'm pretty sure most people who use one have come to a decision based on convenience or other lifestyle choices.
My mother had this exact model in avocado green the 1970's.