A bit more sure. Although generally power scales mostly with the number of chips (or number of dimms). The graph mentions SDR, DDR, and DDR2 for a factor of 6 decrease in watts per GB.
Presumably DDR3 and more important DDR3L have continues to improve the watts/GB.
Generally the CPU/GPU and LCD are the leading consumers of power on laptops. LCDs get somewhat warm, but have a large surface to dissipate heat from. CPUs on the other hand often need active cooling, where dimms (generally) do not.
Seems unlikely compared to a 28 Watt CPU and a 500 nit 13.3" display that the 16 -> 32GB upgrade would be particularly noticeable. Especially when apple claims that the low end and high end models have the same battery life, despite the low end model having a 10% larger battery and lower power CPU, GPU, less ports, and no touch panel.
Increased power consumption with higher RAM may be true.