@Stormkeep yes it stacks up. I dont have the % by hand, but it really pays out.
For the thermostat a simple trick I use: I make always a hot and cold weather home outfit. Warm Socks and Sweaters for winter, light clothing for Summer, maybe a bikini or something and let them wear at home.
I dont now, I have a "garden" on that lot,so I built a pool and a kiddy pool to cool my Sims down. I guess ice cream does work too... But I'm not yet sure about pool and ice cream, haven't played the last week and I can't remember :D