I love my slow cookers and have been using them a lot during the hot weather.
I have a biggish Crockpot with a non-stick coating. This can be used on the hob if you want to brown things over a direct heat before starting the proper cooking process. It isn't dishwasher proof and you can't use metal utensils in it. It gets used for loads of things - roast joints, casseroles, curries, soups etc and is large enough to cook a 1.5kg joint of meat plus veggies for 2 or 3 people. It also has a timer function for up to 8 hours plus a Keep Warm period of (I think) up to 4 hours.
My smaller one is Lakeland's own brand with a ceramic, dish washer safe, inner. I got it mostly for making porridge overnight in winter - chuck in the ingredients, switch it on Low at bedtime and, hey Presto, breakfast's ready when I wake. It's also very useful for poaching smallish quantities of fruit - plums, gooseberries etc or any veg that can't be accommodated in the big Crockpot.
The kitchen stays much cooler than when using the oven and, although they are in use for longer, they use much less power than the oven so electricity use is reduced.