Hi @dublove, in short, the exact timing of energy usage is not considered in that way.
If Bulb customers use 100GWh in a month and Bulb pays some renewable generators to ensure that they’re putting 100GWh into the grid during that month, the exact time that they put the energy into the grid does not really matter (and they have very little control anyway).
So one day we may have no wind, no sun and little hydro generation (not quite sure why but maybe) so perhaps Bulb customers use more energy for their cups of tea than there is available.
The next day there’s far more renewable energy so all Bulb customers have their green tea (pun not intended), and also a few hundred thousand other people in the country unknowingly also get a cup of green tea.
As renewable generation starts to make up more and more of our supply percentage, clever things like battery or/and pumped hydro storage are going to have to be employed to more accurately balance the renewable supply to electricity use, but right now, almost all of the balancing power in the UK comes from fossil fuels.