For low GPU load with a leisurely-paced game type (with no opponents), I quite like "The Settlers" franchise but that got crappier the longer it went on. The 2nd iteration was probably the best although III, which I have now in case of emergencies, is pretty good.I have had my Dalek air-conditioner running every day (I have a health issue with heat) and not felt like running anything with high GPU load - just to stop my toes from getting hot. I tripped over a daft looking thing in a Steam sale - turns out to be a really fun sub-£10 peep building game but with Space Whales (not had one of them yet). So what I am up to is playing with hexagons on little planets in "Before We Leave".
Before We Leave on Steam
Before We Leave is a city building game set in a cozy corner of the universe. Nurture your Peeps and their surroundings while rebuilding and rediscovering civilisation. Settle new lands and planets while avoiding hungry Space Whales.store.steampowered.com