Hey Prairie Stash, it's the other way-round. Insulation is much better on the crock pot than today's gas ovens, and most "gas" ranges are set up as gas cook tops with electric ovens due to the difficulty in maintaining even baking with gas. Of course gas cooktops suck for efficiency, but are quite responsive.
Now, if we we're talking an early 50's Maytag 'dutch oven' it'd be a different story. These were heavily insulated and designed to burn gas to bring the entire chamber up to temp. You'd then switch it off and bake a few hours without any additional heating. Late 40's, early 50's energy wasn't as cheap as we think it was and appliances were designed for efficiency up to around 1960 when rates started dropping and features started to dominate marketing instead.
Gas water-heating is a different matter; if you dont' have PV solar, then gas is superior in this application.
I have very limited experience with gas ovens, it was a wild guess. So I dug deeper and found this site:
http://mindofthemother.blogspot.com/2011/03/crock-pot-energy-efficient-dream.htmlFrom there it says, it depends on how you cook.
As for the insulation, I forgot to account for the lower temperature of the crock pot. Lower temp and less insulation in the crock vs. Higher temp and higher temp in the oven (standard oven use when roasting). So, if you cook in the oven at a lower temp (mimicking a crock pot) the gas oven is cheaper; cause a typical oven has more insulation than a crock pot. What makes them lose heat is the higher temperatures, heat loss is a function of the temperature differential and the insulation, you're right the crock pot can lose less energy, at lower temperatures, but that doesn't mean better insulation.
If you wanted to save money, use your gas oven as a crock pot. You can cook, with an oven, the same way as you cook with a crock pot (long and low). That's the lowest energy usage, it utilizes the lower energy of lower temperatures (crock pot style) with the ovens superior insulation.
We use our oven as a dehydrator, super low temp, it consumes far less energy then if you're roasting meat. That's the problem with the comparisons, it doesn't account for cooking style differences. There's no way my fruit leather is consuming the same energy as my fish sticks (per hour), since they cook/dry at different temperatures.
No simple answer, cooking style is key. Not all food tastes the same cooked in the wrong style (roasting vs. simmering).