PC in a campervan?

Hi there,

In a month or two I'll be having to move into a campervan and would one day like my pc and a small monitor to be in there.

Can anyone tell me which things I need to know in terms of the power/electrics?

For instance, if I use some software to find out what the computer pulls from the power source and then working out how much power I would need in the camper?

Any help or directions is highly appreciated

Thanks