The important thing is that the rules for using publicly financed goods/services are the same for everybody. If you pay for your electricity of course you are free to choose what you do with it.
This is not the same as with roads though, since they are a finite resource (whereas, arguably, electricity can be seen as infinite in this case). You can't ask people to pay for roads which they then can't use because they can't afford the tolls for it. It's already bad enough that so much tax money flows into building roads, which can only be utilized by people wealthy enough to own and maintain a car in the first place. (I'm reading the book "Happy City" at the moment, so this topic struck a chord with me)
If you make $550 per day, $40 is 7% of your daily income; if you make $82 per day, it's 49%. That's not the same for everyone. Of course, there are people who make well more than $550 per day and people who make significantly less than $82 per day.
By that logic, almost every single rule in this world is 'unfair' towards the poor, because of course things cost disproportionately more for the poor.
This is not the same as with roads though, since they are a finite resource (whereas, arguably, electricity can be seen as infinite in this case). You can't ask people to pay for roads which they then can't use because they can't afford the tolls for it. It's already bad enough that so much tax money flows into building roads, which can only be utilized by people wealthy enough to own and maintain a car in the first place. (I'm reading the book "Happy City" at the moment, so this topic struck a chord with me)