I don't know if people know this, but using it all day (say 8h) costs between 0.7 and about 14 kg of CO2 in the US, depending on which region's grid power they use (or, if they run off of generators, the gCO2e/kWh might be very different from these bounds). With 225 working days per year (assuming no night or weekend use), in the worst region that's 50% of the CO2 the average european person uses in a year, just for this assist function; in the best region (a few counties currently running on 100% hydropower) it makes no difference of course because the energy is running down the hill whether you use it or not. Maybe it could otherwise have been exported or stored but there's only so much interconnect and storage
Edit: and this 15$ subscription (again assuming 225×8h use per year divided by 12 months) uses the equivalent of about 150€/month worth of electricity at the rate I'd pay at home. That sounds close to the cost price (ignoring capex on the servers and model training) Google would be able to negotiate with electricity providers. Would be interested in how this works out for them if someone knows