Hey Adrian, Bullfrog power works out to be approximately $1 a day more than standard emission intensive suppliers. On an yearly average I use around 650 kWh (the amount that I used last month) which is very low, so my bill isn't very high.
Here's a website that will give you an idea of what your bill would be. I'm pretty sure it's not affiliated with bullfrog power but it's what I used for reference before signing up.
link Click on "put a little green power in your meter"
Bullfrog powers website
link