Got my Amana portable air conditioner in mid-July, just barely ahead of the anticipated heatwave (Dog Days has always been mid-July through late September here). Then no heatwave! First time in 20 years. When the outside temperature is hotter than the inside (say 90 degrees inside & 95 outside) then cracking windows does no good, and a window fan just turns into a heater, so those days is why I dropped near $400 on an air conditioner. Still a bit POed that I never got to test it, but oh well, it's here for next year.
I rent, so not much I can do about insulation. Landlord made a huge mess for me to clean up two years ago, by ripping out my windows, and sticking in giant double-pane insulated ones. Not keen on a repeat performance (ceiling to floor scrubbing), so I'll not be putting any ideas in his head. Utilities is included in the rent, so not my problem anyway. I been here maybe twenty years now, and never used the installed wall heater. I like cold nights sleeping under covers, and within a few hours after dawn the place starts to heat up....without the window fan going year round it would feel like a foundry in here.
In my case, during the hottest part of summer where my AC stays on constantly during the day, it saves me a bit of money to turn it off and crack a few upstairs windows if I wont be back until after dark. In the winter I just leave the heat on since nightfall doesn't help correct the temp.
As for ramp-up power usage, I'm not sure about heating systems, but I'm pretty sure AC systems are operating at 100% power usage any time they're on.
If you're really looking to cut some costs during the winter, invest a little time in making sure your place is well insulated. I'm pretty sure you can rent a thermal camera to track down hot/cool spots. If you're feeling really hardcore, you might also consider just turning your heating system way down and using a space heater in the rooms you use most.