In general, renewable energy sources are much more diffuse than concentrated fossil fuels.You need a larger surface area to capture this energy using wind turbines, solar cells, ...

This means we will need to transition from centralized to decentralized energy production.

they bear extra costs related to the need to change your transmission framework. Moreover, technology is still "fluid", so you may end up with obsolete installations very quickly.

Renewable energy sources are more volatile and has less efficient. also it requires more capital cost. the technology to convert it into useful format requires scale down of cost with larger production.

In terms of drawbacks you have :

1- intermittencies of RES and their low predictability create new system costs.

2- Transfer of costs toward the other generation technologies to this first element : increase in energy reserves and costs / or risk of local network risks.

3- increase of (social or private) costs for managing network congestions (due to intermittencies) and network development and planning activities.

https://energy.gov/sites/prod/files/2013/11/f4/55296.pdf

http://www.energy.ca.gov/renewables/tracking_progress/documents/renewable.pdf