Do you have a BIG power bill or does Cubase lighten the load?
Biggest bill is for heating, next was lighting but I’ve gone all energy saving on that now 
. Not that my studio would be classed as BIG. Studio gear doesn’t really gobble that much power, not next to heating!!!
I live in a cold northern climate; furthermore in one of the two worst snow-belts in the world (the other being in Japan). My studio has no heating or air-conditioning. It is underground and stays reasonably cool in summer. During the winter, it is entirely heated by gear as long as the rigs are fired up and running. It’s a great incentive to work, so as to stay warm.
My desktop draws 140 to 200 watts depending on what it’s doing. The iPad charges up to 100% in 6 hours on a 10 watt charger and gives 10 hours of runtime; that’s 6 watts an hour vs 140. Cubasis on the iPad is… a little underwhelming for a finished work but ideal for sketching out rough drafts, perfect for general Internet goofing off and much easier on the wallet and the planet’s carbon load.
It all depends on definition of “big”. What is big studio and what is big power bill? And it’s also depends on which kind of equipment you’re using: valve gear consumes a lot of electricity, analog transistor gear less and digital gear/computers even less. There is no “typical” “big” studio around there. They are all unique.
And as others noted: it’s also about climate your studio is located at. Hot/humid: needs a lot of A/C. Cold climate: sh*tload of heating (like in my case). These could easily be magnitude greater than what your equipment consume.
I have not measured the current draw of my little home studio, but during mostly analog days (8-tr R2R recorder, console, MIDI sequencer PC, about dozen of ext FX boxes) I had to have a power-up sequence to avoid blowing a fuse (10A/220V = 2200W) but after moving into the mostly digital setup this have been unneccessary and one master power switch is enough.
But … the answer to your original question (if it was like “does a DAW save power compared to full-blown analog studio?”), the answer is: H*LL YES! A single computer (150 … 500W) can do the work of multiple analog tape recorders, a large-scale mixing console, 100s of valve-driven FX boxes, etc, etc.
I am on timed usage for my power, so I don’t mind a bit of a bash after midnight (or 10pm when off peak kicks in)
I know many studios have cheaper rates during the evening and blocking out sessions during the day would be expensive, so I am wondering how many “big” or “real” studios have time-of-use as standard.
Just remember to rubberize your kit, MIDI Boy!