Does the offshore wind energy costs include externalities of fabricating, assembling, shipping, installing, maintaining and decommissioning the turbines? Does it also include bird losses and whale harms?
Does the gas turbine include externalities of fabricating, assembling, shipping installing, maintaining, and decommissioning oil drilling rigs? And of shipping, storing, and burning the gas? And the climate change caused by gas leaks? And the harms to humans, the fishing industry, and bird losses and whale harms by oil spills (I know you really care about those)?
I really want to know how in the hell whales are getting stuck in wind turbine blades. I want to see a video of this happening.
There's also the externality of paying for the natural gas, which is passed on to the consumer in the form of higher energy bills.
It probably also makes sense to include the $800M we are burning per day right now on patriot missiles (assuming the stockpile hasn't been depleted yet).
The argument is that vibrations of the wind power plants at sea disturb the whales.
Paying for the gas itself would not be an externality. Externalities are for example the worldwide damages caused by extreme weather which is caused by climate change, health problems caused by air pollution or the usage of clean water for cooling
Normally, I'd agree, but in this age of massive corruption, you need to be careful figuring out who the stakeholders are. The purpose of these new fossil plants is not to produce electricity. Their purpose is to line the pockets of the ultra-wealthy people building them, and of the politicians accepting bribes to get them built.
Fueling the power plant is an externality for the people building the power plant. You could argue that it increases their costs, but these things are monopolies, with prices set by bought-off politicians. The plant + fuel costs much more than renewables (so ratepayers get screwed), but I'll wager the plant without fuel is still a bit less than solar or wind construction.