Good morning, folks! Thanks for all your hard work on the game. I love it. This post is in no way, shape, or form intended to be critical. I just wanted to share my semi-educated opinions, as a former commercial/industrial electrician and ham radio operator.
I realize too that fun comes before realism, so yanno. But there are some fundamental differences between low-voltage high-amperage DC electrical systems (as you would find in automative applications) and high-voltage low-amperage AC electrical systems (such as you would find in household wiring).
I also apologize if this has been discussed before. As a self-employed type, my day job is busy af (ironic considering that I have the time to write all this at the moment lol), like 60 hour weeks typically. So I don’t really have time to keep up with the github and discord discussion as well as I ought. 
Before I share my thoughts on this though, let’s make sure we’re all on the same page. Please skip ahead if this is old news to you.
These explanations are not meant to be read as me talking down to anyone. I just want to make sure that everyone reading this can be on the same page once we get to the meat of this discussion.
As we recall from EE-101, the power being supplied or consumed in an electrical system (wattage) can be expressed as the voltage on the line (volts) multiplied by the current flowing through the line (amps).
This can be difficult to visualize, being that electricity is invisible, but we can use the metaphor of a water pipe to help. The metaphor starts to collapse if you examine it too closely, but I think it’s sufficient for this discussion.
Imagine that power (watts) are the amount of water coming out of the end of a pipe. Imagine that voltage is the diameter of that pipe, and that current is the pressure of the water in that pipe (how fast the water is moving through it). Thus, we can supply the same amount of water (watts) using a larger pipe at a lower pressure, or using a smaller pipe at a higher pressure.
But if we apply too much pressure, the pipe bursts. Likewise, regardless of how high or low the voltage on a wire is, if we try to pass too much current (amps) through it, it will melt.
The ampacity of a wire (the amount of current it can carry before it melts) is unrelated to the voltage on the wire. Thus, we can carry more total power on a smaller (cheaper) wire using higher voltages. This is why your household power is 120v in the US and Canada, and the power up there on the power lines on the other side of your residental transformer can be up in the thousands of volts.
We also need to discuss the difference between AC and DC power.
DC power puts a constant voltage on the line, and the electrons are always flowing in one direction. The water goes in one end of the pipe and eventually comes out the other.
AC power alternates polarities, crossing over the zero threshold 120 times per second (in the US, Canada, and Japan anyway). The water in the pipe is sucked and then pushed back and forth like you might do with a butter churn. The motion of the water going in and out of the pipe at the other end can be used to do work.
AC power is easier to transmit over long distances, because it’s very easy to step the voltage up and down using two coils of wire wrapped together (a transformer). This is why we typically see it used in household applications. Additionally, since the polarity is alternating, it’s “turned off” 120 times per second (each time it crosses zero volts). If there is a short circuit, this will break the electrical arc sooner, before more of the wire has a chance to melt, and therefore is less likely to set your house on fire.
DC power is more compatible with batteries, which is why it is used in automotive applications. There is no way to store AC power in a battery. You apply a DC voltage to a battery to charge it, which changes the chemical composition inside the battery. Then you hook a DC load to it, and the battery discharges, returning the chemical composition to what you started with.
Some types of loads don’t care if they are on AC or DC power. Examples of this would include incandescent light bulbs (such as in your car; most household bulbs these days are flourescent or LED, which will care what they are supplied with) and heating elements. These loads, however, are still designed to be powered with a specific voltage. You plug a car headlight into an AC receptacle, it will blow the bulb. You plug a household oven heating element into a battery, and it probably just won’t do anything to speak of (other than maybe damage the battery trying to draw too much current, depending on the battery).
Other types of loads however require either AC or DC to function properly. There are fundamental differences between AC and DC electric motors, for example. Electronic devices also require DC power (even those that plug into the wall convert to DC power internally).
(In the coming paragraphs, recall that with wire gauges larger numbers indicate smaller wire.)
So, let’s look at an automotive type electrical system. Low voltage (12v typically), high current (20 or 30 amp fuses are common just for running one thing such as the fuel injection or headlights, and everything is on its own circuit). Such a system tends to use short runs of comparatively thick wire. #10 and #8 are common, and the high-power main battery and starter cables are as thick as your thumb.
(Notes: Some vehicles have a 24VDC electrical system. Mostly military vehicles and older road tractors, although it’s not nearly as common as it used to be. Most automotive fuses are actually rated to 36 volts, and can be used in either application, but all the bulbs, electric motors, etc that run off 24v will be different. DC-DC converters can be used to get 12v out of such a system to power your 12v CB radio and such. Marine applications are typically 48VDC and use entirely different fuses and breakers (which are all stupidly expensive), and again the light bulbs and electric motors and stuff will all be different, but the same sort of DC-DC converter can be used to run your 12v marine radio or whatever. DC-AC inverters which we’ll discuss later can be had in 12v, 24v, or 48v varieties, but the 12v ones are all you’ll find at the local big box etc. The 24v and 48v units are typically only found in off-grid solar power systems or maybe in one of those power wall thingers.)
Let’s look at the household wiring on the other hand. High voltage (120 volts RMS in the US and Canada), low amperage (15 or 20 amp breakers are typical, and many many devices will be plugged into the same circuit). Comparitively small wire (#12 most of the time, although you will occasionally see #8 or #6 powering something like a 50 amp electric oven). Recall the water pipe metaphor from before. Since the voltage is higher, we don’t have to pull as many amps through the wire. So we can use a smaller wire. This is good, because long runs of large wire are expensive.
(Notes: Our household power in the US is actually 240v, but we only use half of it at a time with a common neutral most of the time. Two 120vac lines that are opposite in phase. This only comes into play with stuff like ovens and clothes dryers, though.)
So let’s look at some situations in Cataclysm, and how this might inform what might ought to work and what ought not.
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You hook a car (12vdc) to a building’s household wiring. You take some 12v light bulbs salvaged from cars and use them to light the interior of the building: Realistic. As long as the wires aren’t too awfully long (resulting in a voltage drop and dim lights). Even though the household wiring is small, the lights are a pretty low-amperage load (especially LED lights).
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You hook a car (12vdc) to a building’s household wiring. You plug a refrigerator into a receptacle inside to preserve your food: Unrealistic. The compressor that pumps the ammonia or freon (or whatever they use now) through the system operates on an electric motor. This motor will have been designed to run on 120vac, not 12vdc. A very skilled individual with the proper tools might be able to remove the 120vac motor and replace it with a 12vdc motor salvaged from a car’s windshield wipers, maybe? If the motor was beefy enough to run the compressor. And if it didn’t try to draw too much current and melt the small household wiring (this is probably what would happen if you tried to use a starter motor instead of a windshield wiper motor).
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You hook a car (12vdc) to a building’s household wiring. You plug an 240v electric range into the household wiring to cook with: Absolutely No Way In Heck. Even though the oven’s heating elements don’t care about AC or DC, they are still designed to work at 240 volts. In theory, we could cut a single 240v element into 20 shorter sections and reconnect them in parallel. But recall our equation from before, power = V * A. This oven was already probably running on a 50 amp breaker at 240 volts, so it could be consuming twelve-thousand watts! To supply that much power at 12 volts would require one thousand amps. Even a small oven on a 30a breaker would require 600 amps and element modification to run at 12v. Even the main lugs of a typical household breaker box are only designed for a 200 amp service. There is just no way for this to work. All of the RV ranges I’ve seen use propane.
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You build/repair/find a 120vac portable generator somewhere and plug it into a building’s household wiring: Very Realistic. Most of the stuff in the house would probably run fine if the generator can supply enough power. However, turning on an electric range or a heat pump or something might trip the breaker on the generator, if it isn’t made to supply that much power.
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You build/salvage/repair a 12VDC-to-120VAC inverter somewhere, hook it to your car, and then attach that to a building’s household wiring: Very Realistic. This is the same sort of use-case as the generator above, but remember that these inverters usually can’t supply nearly as much power as a generator unless you operate many of them in parallel (which requires some special control wiring to keep them all in-phase). Running electric ranges, air conditioners, etc is pretty much out of the question. Many of the consumer-grade inverters can’t even run particularly large power tools or toaster ovens. But lighting, computers, radios, small AC motors (fridge/freezer compressors), etc, that kind of stuff would be fine.
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You supply 120vac to a house somehow using one of the methods above. You then salvage a bunch of car headlights and use them to light the interior of the building: Realistic. If you string ten 12v incandescent light bulbs together in series, you can run them on 120v. But like your Christmas dreckerations, if one bulb gets crunched by a zomboi, all the others in that series will go out too. Although given that the building would probably already have lighting, I’m not sure why someone would want to do this.
Uh, I am probably forgetting something I wanted to mention. If so, I guess I’ll reply to myself, lol.
Again, thank you all for all your hard work on this fine game. None of the above is meant to be critical at all, just to share my thoughts. I haven’t contributed enough to the game or community to earn the right to complain, and even if I had I don’t see anything to really complain about with this building electrical stuff. I am sure that much of the above would be too tedious to implement anyway. Although I do worry a smidge that being able to hook cars to houses and use all the household appliances without modification would be (1) unrealistic but more importantly (2) might make the game too easy starting out. But yeah, I’m not going to complain, whatever y’all decide!
Thanks!!!