If we have to use fossil fuels to manufacture renewable plants, doesn't it mean that renewables are useless ?  

One of the more frustrating arguments you can ever have with a doomer about renewable energy is the weird "solar panels (or wind turbines" aren't built entirely using renewable energy today and therefore they never can be" line that they like to trot out. Resilience has a post from Cassandra's Legacy looking at this bizarre belief (Still taking a mildly pessimistic viewpoint but its an improvement on the collapsist stuff you still see at places like peakoil.com) - If we have to use fossil fuels to manufacture renewable plants, doesn't it mean that renewables are useless?.

In this post, Marco Raugei makes a fundamental point about an often raised question: if we have to use fossil fuels to manufacture renewable plants, doesn't it mean that renewables are useless? Raugei's answer is a resounding "no". In fact, the EROEI of fossil fuels acts as a multiplier for the final EROEI of the whole process. It turns out that if we invest the energy of fossil fuels to build renewable plants we get an overall EROEI around 20 for a process that leads to photovoltaic plants and an even better one for wind plants. So, if we want to invest in our future, that's the way to go, until we gradually arrive to completely replace fossil fuels!