Modern electric mowers are actually very quiet, they're not your parents electric mower that's for sure lol
Mine is so quiet not only do I not need to worry about ear protection, you can't even hear it from inside my own house so def none of the neighbors will be able to hear it either lol
What lawn mower do you have that is that quiet??? I have a Ryobi electric push mower that I bought last year and while it's way quieter than a gas mower I would feel incredibly rude using it early in the morning.
And noise is different depending on time of day. Ambient noise is a lot lower in off-hours, so your mower would sound louder than it does during the day.
Ours merely hums, wouldn't think the noise would make it through a window unless you were within 10', and even then, that might not wake a sleeping neighbor.
I sincerely hope you never test this theory. I many people in this thread are severely underestimating how little noise is needed to be disruptive in the early morning.
My local noise ordinance sets the maximum permissible noise in residential areas during off-hours (10pm - 9am on weekends) at 45 dB. That can be exceeded by 5 dB for 15 minutes, 10 dB for 5 minutes, and 15 dB for 1.5 minutes. Lawnmowers are an exempt source of noise during day hours only. I guarantee if you were my neighbor your mower would be in violation of noise ordinance at night.
Plus, assume some people are sleeping with their windows open. Especially in mowing weather. Windows open overnight may be the only way they keep their house bearable during hot days.
I was riding up the street on my bicycle the other day and actually stopped and backtracked to ask my neighbor what kind of mower he was using because I was so impressed at how quiet it was. Turns out it was a Ryobi (one of their brushless 40V models, which might matter).
It does say "brushless" but they've got a fair few different varieties. I don't know, I mean like I said it is significantly quieter than a gas mower. It's a good mower. But I don't think it's anywhere near quiet enough to consider using it during off hours.