> How much electricity can plausibly be saved this way?

About third of what was used before.

> And how does that compare to the energy required to reprogram and possibly renew all these signs?

That's cost of doing business and a one-time thing.

> About third of what was used before.

How much is that as a fraction of the total electricity consumption?

Savings start with all non-essential things first.

According to the source linked in the top comment, we are looking at a total consumption of 113.000 MWh per year for those displays. One third of that is at least around 30.000 MWh of saved energy.

So 0.005% at 560 TWh total consumption.

Well, in that case we shouldn't improve anything as long as children are starving to death in this world. That should be our only and biggest "bug" to fix. Feel free to recommend another one, but we'll pause all other improvements meanwhile. ¯\_(ツ)_/¯

How about not jeopardizing the economy by ever more constraints and instead investing in better energy technology?

Maine banned all billboard style advertising decades ago. Our economy functions just fine thank you.

The action is super visible though. Sometimes that's the most important thing. /s

About 113 GWh, apparently. Total power usage is 400-500 TWh. So a drop in a bucket, but many of these measures will add up to a couple of percent.

No idea how much energy it takes to reprogram/renew the signs. If they just turn them off, very little, I suppose.

A lot.

A coder peddling the entire time required to adjust the timing would be lucky to power a single billboard for a night.

Digital billboards use thousands of watts, overall, that's several times the energy consumption of a typical household, the power bill is thousands of euros a year.

So I guess that's worth it, even if some additional hardware is required.

You also need to consider all the future signs as well in the equation.

> And how does that compare to the energy required to reprogram and possibly renew all these signs?

That's just energy they would have otherwise spent on making us buy more stuff.