I'm a sceptic here.
The reason I plug something in is because I want it to consume electricity. The reason I put a light on is to see. The reason I put the heating on is because I'm cold. At which point am I required to suffer for the sake of energy efficiency? Just how many people leave their TV's in "eco" mode all the time compared to how many want to view the damn bright TV they bought based on the picture quality they saw in the store?
Now, of course there is some waste - people leaving lights and heating on and leaving the room, but no amount of computer intelligence can tell you why they did that. Maybe their room is fricking freezing and the budget for heating is separate to the budget for repairs despite their protests? Maybe they are going to be back and forth a lot. Maybe they have wedged to door open so they can see to change the bulb that blew in the other room.
Even on a larger scale - if you turn off motorway lights at night, yes, most of the time you save. Because it was always such an inherently wasteful exercise to have them all night. But beyond that, if you don't turn the lights on, you might as well not have them in the first place and have cars use their power to supply light. You'd save more by knocking the lights all down, disconnecting them from the grid (and thus removing lots of cable loss) and melting them down for cash. They were on, not because we couldn't put a strip in the road and only turn on when they detect that a car is approaching, but because the cost of switching them on/off all the time and installing and maintaining the systems to do so (and the associated strains on the power network) cost more than just leaving them on.
As soon as you scale city-wide, the problem worsens. More controls, most of them idle or never switching (because the area they monitor is just that busy), more data to process, more cables and installation to handle them all, more tough decisions to make, and more people affected by a "global" decision that has nothing to do with their demands/uses/personal habits. Good for Cisco. Bad for everyone else.
Personally, I find even "traffic management" the bane of my life. I actually plan routes to avoid traffic lights and clever management systems (and whoever thinks traffic lights on a roundabout are a good idea should be shot). If the average switching time of a traffic light sequence is 30 seconds, say, I have to multiply half that (the average time I'll wait by arriving at a random time) by the number of lights I go through. Soon it adds up to the point where I actually get to work quicker by driving down backstreets and residential roads, over speed humps, through width restrictions, past speed cameras, and through twice the number of roundabouts to get to a motorway that goes miles out of my way to loop back towards my destination later. I actually use less fuel, less emissions and arrive at my destination quicker on on the same time (on average, of course), but I am working AGAINST every traffic management measure that exists and not improving the situation for anyone else.
The "intelligent" traffic management at South Mimms this morning kept feeding more and more cars onto a grid-locked roundabout despite having signals at every entry and at four points on the roundabout itself (and police cars on scene for over an hour). There is no reasonable explanation for that, no matter how removed from the jam you are when you analyse the data. An intelligent system would have blocked all the entrances in seconds, kept the roundabout on green and then fed in cars from entrances one at a time only when it was clear. Larger queue on the motorway for the exit to the roundabout, but a chance of actually NOT ending up in a deadlock situation. And nobody breaking down due to overheating just on their way off the roundabout blocking EVERYONE else, and no horrendous amounts of traffic fumes to crawl one inch forward every five minutes.
I don't see an intelligent city. I see a large contract for a sensor manufacturer and infrastructure companies. An intelligent city would build a larger damn motorway, extra motorways, underground motorways, better public transport, provide incentive to work from home, etc. Similarly an intelligent energy monitor would flash up "support nuclear fuel, scrap all the wind turbines".
It's an exercise in looking busy and spending money on a problem that could be fixed in a year or two by enforcing an unpopular decision.