https://i.imgur.com/Yudewrq.png
If your pink is Atlantic and your purple is Eastern, I can live with that.
Yes, purple is Eastern.
If we really wanted to reduce energy consumption in this country, we would run standard time during the summer and DST during the winter. We got it backwards. In the winter when people are trying to heat their homes, maximizing the waking hours of daylight helps reduce energy consumption (the sun is a natural heating source). OTOH, in the summer when people are trying to cool their homes, the sun being out doesn’t help that effort and minimizing the waking hours of daylight would help reduce energy consumption.
Nnnn... so, first of all, it needs to be kept in mind that only 40% of energy used by buildings in the US is used by residential buildings. To get the full picture you can't just focus on what people are doing in their homes, you need to also focus on what businesses are doing.
As things stand, the daily temperature in the summer tends to peak around 5 PM (with DST), with it being fairly close to peak for a few hours before and a couple hours after. This peak occurs right around when a lot of people are leaving work.
In a scenario where standard time were used in the summer, this peak would be at 4 PM instead - and this would have the effect of creating a larger overlap between the hottest hours of the day and the hours of the day when offices (among some other commercial, industrial, or civic/institutional buildings - depending on their operating hours) are occupied.
Might this be counterbalanced by a smaller overlap between the hottest hours of the day and when residences are occupied? Maybe, but there would not be savings realized during this time period in residences where someone is home in the afternoon.
Something else to consider here is the impact that a clock shift has on the overlap between occupancy and when an onsite solar PV array is generating electricity. Currently, areas with a lot of solar production are already starting to see some of their peaks for utility electric demand shift later into the evening, with it starting to be driven by when solar production drops off rather than by when air conditioning usage peaks.
A shift to standard time in the summertime would exacerbate this by increasing the number of hours in the evening/night when people are awake and using electricity but solar PV systems are producing little to none of it.
This would then, in an a PV-dominated area, increase costs by increasing the required energy storage capacity. And this would generate a gross increase in energy consumption simply by virtue of the fact that energy storage is imperfect; over the course of charging and discharging batteries you lose some energy to heat, and you also then have to consume energy to keep the batteries cool.
I don't think it can reasonably be asserted with any level of confidence whether the impact on overall nationwide energy consumption of switching to standard time in the summer would be positive, negative, or a wash. There are too many different variables involved.
Even if we were to empirically try it, there are going to be confounding variables that cannot be fully controlled for.