This may not be the post you're looking for.
I might write a post about the opportunities offered by electricity in a fantasy world; I might essay to explain how and where there are differences between traditional electricity and magical-generated electricity; I might pinpoint the development of electricity over the last five hundred years, or talk about ways to modify Volta's Pistol with magic to make it a death weapon extraordinaire. I might ... but I haven't the motivation.
As these posts deepen into the realms of higher technology, it becomes more valuable to discuss what the lack of a particular technology has upon the D&D world, rather than what's added. As we dwell in a world where electricity is as pervasive as air and water, we should give some time and contemplation to a world where none exists. After all, none did, and very recently.
The first comprehension is always the modern presence, and therefore the medieval absence, of light. After all, as the gentle reader looks around, you're surrounded by 'artificial' light, quite probably all of it electrically based (for all I know you're burning a candle right now). You're reading a computer that throws light, and whether you're sitting in the glow of little vampire lights on your tower, your mouse or your phone, or in a room flooded with flourescents, you can't help but think that if there were no electricity, it would be a lot darker right now. If you're outside, then you have to consider that its going to be much darker soon.
The absence of all that light is going to mean a lot more than you can't see what you're doing ... its also going to mean you're doing a lot less. Most definitely, either entertaining or educating yourself, the two mainstays of human activity when not actually working to keep yourself alive - which of course, you're going to do almost exclusively in daylight. In the 19th century, there was widespread working at night prior to electricity, mostly due to the increased availability of burnable fuel - coal-tar gas, petroleum gas, and even whale oil, the production of which leapt once steam manufacturing increased the rates at which ships could be built in order to hunt for whales to find the oil that would keep the lamps lit while making more things.
But this is all Industrial Revolution stuff, and we don't play D&D during the Industrial Revolution. We don't even play it during the enlightenment, when newpapers became widely available, which became the primary way in which people educated themselves in the late 17th century. Newpapers, one will take note, don't throw light, and therefore were expensive to read outside of daylight hours. That's a difficult thing to consider ... that if you wanted to do something at night, you had to worry about more than your ability to do so - you had to worry about how much it would cost you. Burning a candle, which you must replace when it gutters out, is more tactile than a bill you receive online; you didn't burn them unless it was important. We love to tell stories about Abraham Lincoln reading books in his cabin by candlelight, as though he were poor ... when in fact, his family was doing awful well to be able to keep a kid of theirs in burnable fuel.
We so casually conceive of a party sitting around a fire in the evening, after a long day's march, eating haunch of roast beast, whittling stakes or whetting a sword, that we tend to forget that once the sun's gone down, there really wouldn't be much else a party could do. The popularity of story telling wasn't a motif of the period because stories are really cool and gosh darn, the people just loved them, it was because your primary source of entertainment during those hours when you weren't doing the things that needed light could only be done with your ears.
How quaint and soulful it is to imagine people sitting around a fire, listening to the elders tell tales of the past, the family gathered together in the glowing light, so much cheaper than candles. And how easy is it to forget that most of those stories were out and out lies, and that they included things like that the Jews murdered Christ, or that people who didn't suck up to the Church daily were going to hell, or that children who did not obey their parents would grow sick and die because God wanted it that way. Far more of the tales were socially-motivated lies and propaganda, intended to encourage people to obey and act in accordance with social norms, than cute stories about fluffy bunnies and princesses in love. The reader will get a far better idea of what sort of 'stories' were told by sitting in a bar in Bowling Green, Kentucky, than meeting with the Beatrix Potter fan club in Rye, New York. The world was a nasty, dismissive, oppressive place, and you can be damn sure the elders made their younger clanspeople well aware of it.
Education - of the sort where you learn something that's true and you can compare notes about it - was everlastingly rare. It was available only to those people who did not have to spend every hour of daylight supporting themselves ... because they had others supporting them. The reason why so much science and social thought developed among the English clergy for hundreds of years was because, beyond having to produce a sermon once a week, there was plenty of time for those people during daylight hours ... when it cost nothing to read, write, experiment, produce artistic works, etc. And if you didn't happen to have the will yourself to do this sort of thing, but you did have a lot of time during the day, you amused yourself by patronizing some other creative soul with your wealth; this meaning, naturally, that you could go around and bug him once or twice a week, getting the feel for creativity without the need for discipline or talent.
The ignorant stayed ignorant for century after century not because the various powers kept the knowledge from them, but because there weren't enough daylight hours to indulge in things that didn't stop you from being killed by starvation or the weather.
Not that candles produced in the 1300s very bright, either. If you think you're getting a feel for the medieval atmosphere by turning off the lights for your game and lighting a few candles, think again. Candles for most people weren't made from the same stuff as your candles, and beeswax was wildly expensive. Candles were largely made from tallow - pig tallow, if you were lucky and doing fairly well. Otherwise, you got by on vegetable tallow, which burned quickly and did not exactly light up a room. Additionally, it took a lot of work, and so it was reserved for particularly important times of the day - ten minutes a day, perhaps, for eating. Certainly not for reading.
So consider that the Bible doesn't offer much solace during the long hours of night ... so logically, if the devil was going to get you, it would be when you couldn't scan a few tracts in his face. Of course, the common people didn't read, and didn't own Bibles, which weren't written in the vernacular anyway ... what would be the point? If Gutenberg had run around making bibles for the poor in the 1450s, even in German, French, Italian and English, there was no light to read from them. We like to think that once the Bible was finally translated, everyone ran out and got a copy ... but of course, that really only happened when reading around the table became an option two hundred years later.
Let's go back to your ears, now, and consider the influence of electricity on those. What are you hearing right now? Energy, going on all around you. And it is always there. If we get rid of the blower in your office, or the furnace, there would still be the soft whine of your computer. There's always some noise in your life, because something is always humming or whining, somewhere nearby. You may not be able to hear it now ... but if we mask out the louder things you don't pay attention to, there would still be the quieter things you would learn to hear also.
In fact, unless you've taken deliberate steps to leave every kind of device behind, you've probably not been without them your whole life. Even in the country, you can hear the lamps you're carrying around your campsite; the distant cars on the highway. When I used to spend some of my teenage nights with a telescope in a farmer's field outside a cabin development near Sylvan Lake in the early 80s ... I could yet hear the cars on the secondary highway three miles away, even though it was midnight. It's very hard now to find somewhere truly remote - and truly quiet - and we can't begin to imagine it.
James Fenimore Cooper's inevitable twig snapping would have been like a gunshot to ears that were not assailed day and night by decibal levels in the triple digits. Even a double digit sound would be rare off the guild streets of a town, or where people weren't gathered. There would have been little need for a town crier to cry quite so loud, since there would be less to cry over than you standing up to shout politics at your university's Speaker's Corner.
So ask yourself - are night watches really necessary? Parties are so used to setting them up, assuming that creeping up on a sleeping person is as easy in the 15th century as it is today ... despite the fact that six hundred years ago, it really was freaking quiet. The lack of electricity, which runs everything with a little bit of noise, would attune a party to recognizing every imaginable sound within a hundred yards just as if it were a light shining in their faces. A thief would have to be a lot better at moving silently then than he or she is now. There's no ambient noise to cover it up.
Which is why, I think, I've never liked the thieves' hear noise ability. Honest, this ought to be someone who automatically does it ... or at least, there would have to be considerable mitigating circumstances that denied the success. 10%? You might as well argue that I only have a 10% chance of seeing a light when its turned on.
This has been going on for awhile, and I have to cut it off. I'll just put in the reader's mind a few thoughts about how much of a day's fare was eaten raw because building a fire and cooking isn't as practical as running a stove, even in the house. Or how much more comfortable a party member would be building a fire, having built them every day of their lives since infancy (which I admit, I hadn't considered). Or that the ends of your fingers were probably burnt a hundred times from handling metal pots buried in coals. Sex would be almost a completely tactile experience - you could go decades without ever seeing your wife or husband naked, not because they denied it ... but because except for dangerous forays into the isolated woods, nakedness only happened in the dark. There are other reasons the 18th century invented porn, as light because more available to all.
Just general food for thought. I'm sure others could come up with more. Remove electricity from the field of human comfort and habit, and its truly hard to envision what the world really would have been like. You almost certainly cannot, not in the environment where you live.