The quad cores use a lot more power because Intel uses processor binning to "create" laptop CPUs. Basically, laptop and desktop CPUs are the same thing when they come off the production line. Intel tests each one, and the ones which are able to function properly at lower power and voltage get binned as laptop CPUs. The rest become desktop CPUs.
The chance of both cores in a dual core CPU operating properly at lower power and voltage is fairly good. The chances of all four cores on a quad core CPU operating properly is not so good. So there's a shortage of laptop quad cores. To make enough quantity of laptop quad core CPUs, Intel has to ease up on the requirements. Which means they run at a higher voltage and burn a lot more power.
The TDP is the recommended cooling, so corresponds to the maximum power the CPU could consume (some don't even reach this max). Power consumption at idle or low power is much lower than the TDP. But because the quad cores operate at higher voltage (in addition to having 2 extra cores), they will use more power than a laptop dual core.
It's possible to get lucky and get a quad core which will undervolt like a champ and get great battery life. But it's exceedingly rare. I wouldn't count on it. If you really, really want a low power, low temperature laptop, I would stick with the dual cores. The quad core laptops with great battery life just stick a huge battery inside (70-100 Wh, vs about 20-40 Wh for the typical dual core laptop).
Power consumption is non-linear though. Increasing clock speed by 10% results in much more than a 10% increase in power consumption. So it's really the extremely high clock speeds you want to avoid. If you're ok with somewhat high temps and moderate battery life, you can get it from a quad core by (1) turning off hyperthreading in the BIOS, (2) turning off Turbo Boost (set max process state to 99%), and (3) limiting the max speed (set max processor state to something lower than 99%).
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