I tried the laptop route once. Hated the graphics chip, went back to custom building desktops at super low prices. Much better PPP (price per performance). Some hardware for the PC can reduce power consumption considerably. Enable the c-states for your CPU, avoid buying "cutting-edge" GPUs, buy green HDs (SSD if you can afford it), and take advantage of power savings in Windows. Some power saving features can be annoying at times (disable hard disks), but it does drop the consumption considerably. Putting your machine to sleep is also better than doing a hard boot if your sleep times are within a day or so. Toms Hardware has some specs of what certain hardware runs at. Intel chips are generally better then AMD in terms of wattage. You can cook food on most AMD CPUs. Most desktop CPUs tend to operate in the 80 - 130 watt under load, 30 - 50 watt idle. GPUs are by far the elephant in the room. Some cards can draw up to 350 watts. That leaves 50 watts left in my PSU!
I would be power conscientious for environmental reasons before my wallet, but often the two go hand in hand. Notebooks are good on power, but the lack of hardware diversity and ease of replacing parts is what turns me off. Had the laptop industry evolved like the desktop industry, I would have stopped buying PCs over a decade ago. Alas, such as it is, cheap hardware and cheap quality at expensive prices is a major turn off. For mobility and even doing Linux builds, I rely on my netbook. Like 5 watts on standby and with Linux console, there's virtually no power draw even under use. I sometimes do long train rides (4-5 hours) and can almost coast the whole way without recharge. It's not for everyone, but I love these little guys.
I wouldn't bother to much on solar power. Most portable packages are gimmicks built with low quality. Better to spend \\$100 on another lithium battery to extend your use then spend \\$100+ on a portable solar unit with materials bought and constructed from the lowest bidder. A more versatile setup is to invest in portable battery chargers. They generally come with a high capacitance lithium battery that you precharge. You then plug your devices into it and it acts just like a normal power source until the battery runs dry. About the same in price as a laptop battery, but with more utility.