So, why now?
Well, with renewables climbing up everyone but the government's and the fossil and nuclear industries' agendas, the question of whether we can keep the lights on if the wind doesn't blow and the sun isn't shining is a constant challenge to advocates of low-carbon energy.
The task of demonstrating that renewables are up to the job isn't easy - it means being able to look at supply-demand balances over long periods of time accounting for changing weather, and through each of our four seasons.
Our model underpinning the report enables us to do just that - on an hour-by-hour basis over 11 years of data. A big step forward.
And what does it tell us?
First, that we can seriously decarbonise the UK's electricity supply, while adding millions of electric vehicles and electrifying 25% of heating with heat pumps, with the right kind of political ambition. Our scenario envisages 85% of power (that's electricity) being delivered from renewables in 2030.
Second, that none of this is possible without radical reductions in the amount of energy we use to heat our homes and workplaces - or without sustained reductions in what we already use electricity for today.
Energy demand reduction - you might not be surprised to hear us say - is still the key to unlocking a low carbon future.
To find out more, you can read Greenpeace's blog here.
Or if you really want to get stuck in...the report itself is here.