# residential electrical service question

I am very confused by how home electricity works. So when someone refers to a “200-amp service”, this is what I gather, please correct me where I’m wrong:

• the power company is providing a 200 amp service. So one way or another your devices cannot exceed 200 amps of draw. How exactly is this implemented? And hypothetically, what would happen if you used a main breaker in the service panel that was greater than 200 amps, and you actually tried to draw more than 200 amps? Some other breaker on the power company’s side trips?

• the service panel is rated as a 200-amp service panel. What exactly does this mean? Is it just referring to the size of the main breaker in the panel?

Also, if the house is a multi-family residence with multiple meters and breaker panels, does this mean that each of the units has its own 200-amp service? So in effect the power company is providing N times 200 amps of “service” to property?

I am sure that you will get more technical answers, but in general - yes, you can draw a total of 200 amps from the mains. I am guessing that there will be a fuse, not accessible to you, that would blow if you tried to draw much more.

As for sharing, they will assume that no one will draw 200 ams, and different people use high demand appliances at different times. Not likely that you would all switch on your electric ovens and clothes dryers at the same time. They will be supplying some multiple, but not 200 times the number of residences.

I’ll assume you are on the North American power grid as that is the one I am familiar with. All voltages noted can range plus/minus about 10%. I’ll leave multi-phase options out of the discussion.
Your household electricity is most likely provided by a center tapped 220Volt power transformer. Center tap means that 110Volts to neutral (ground) are provided but leg to leg gives 220Volts. 200 amps on each leg of your 110Volt supply is available. That means if you only have 110Volt devices in your house you have 400 amps available. There are no common residential devices that can draw that much power at 110 volts. Heavier household loads are 220V such as cooking ranges, electric heat sources, dryers, etc.
If you are in a multi residence setup, whether a single building or residential block, you are most likely sharing a transformer with your neighbors. Drive through older residential areas where the power lines are still above ground and you can see maybe 3 or 4 power lines going to different houses from the same pole top transformer. The number of housing units dictate the size. They are not sized 200Amps per residence though. Wasteful to expect everyone to draw max capacity simultaneously. I’ve never seen a chart, but 400Amp service for 4 houses would not be out of line. The larger the transformer, the more energy in excess of 200 Amps is available. Even a single household transformer can instantly generate 10s of thousands of amps for a few milliseconds before the fuse or transformer blows. Non-electronic breakers are even slower. The voltage provided, however, drops as the current goes up. That’s when brownouts occur. Slight overloads further up the distribution network as everyone turns on their AC when the heat is on. Power company substation transformers are slightly overloaded or the generators are maxed out.
Back to the question.
Your breaker panel and the wiring feeding it are sized as a pair. The power company does not restrict your consumption. Yes you can draw more than 200 Amp power for quite some time before your main trips. They work by heat. The higher the overload the faster they heat up and trip. A 10-15% overload will take hours sometimes to blow. A 200% overload should take a few seconds. There are charts on the web you can look for that explains this. Your breaker panel components are designed to distribute the amperage of the main breaker. Each stab the breakers connect to are also sized for a certain load. Probably not 200 Amps though. That means you cannot bring in 200A through the main and send it back out another 200A breaker to some device or other panel through a breaker. I’ve seen 100A sent to sub panels though. The breaker and panel makers don’t make stuff that will create problems like that.
When your 10000BTU portable A/C kicks in it draws much more power than the breaker it is on. I mean the running current on the box may say 10Amps or so but motors draw roughly 6 times their running current at the instant of start gradually decrease as the motor gets up to speed. That is why lights can flicker when they start. a larger multi-residence transformer has more cushion for that event so your lights may not dim. This is provided it is not already running near capacity. Also the resistance of the wires to your breaker panel can be an energy choke point and drop the voltage available to your panel if consumption exceeds their capacity. They also can heat up. Can you say “electrical fire?”

With a 200A circuit breaker in your main panel.

If you remove the main breaker, you can draw as much power as you want. You could potentially dangerously overheat the service lines coming into your house and cause a fire. In any case, you’d still have to pay for the amount of power you use. But 200A really is a lot of power for one house to use, unless you’re running a server farm or growing weed or something.

That just means it comes with a 200A main breaker and enough space for a reasonable number of branch-circuit breakers. Really, you can use any panel as long as the main breaker is the right size. It’s perfectly common for the branch-circuit breakers to add up to a much higher number than the main breaker, since it’s not expected that they will be drawing their maximum capacity all at the same time.

That’s impossible to know without more information. Different jurisdictions do things slightly differently when it comes to multi-family setups.

Ok so this is one of my main points of confusion.

If you have a very old house with say a 40A service and you want do a service upgrade, this typically involves the power company and getting a permit, etc. Which means a service upgrade is more than just popping in a new main breaker in your panel. So, is it that the power company needs to run a new line to your house from the street that can handle a higher amperage draw, because the one that is there now is very old/undersized and can’t handle 200 amps? And also because you may be sharing a transformer (per PoppaSan) with your neighbors and they have to make sure there’s still enough to supply all the houses?

Also thanks to everyone else who replied.

200 amps is the TOTAL amount of electricity your MAIN electrical panel can handle at one time. The maximum. Other people’s panels may be rated at 150 amps, 100 amps, or 400 amps.

It is rare that a typical house would use that much electricity all at once (200 amps). Note that an individual breaker for outlets may say 20 amps [maximum again], but you may just have a vacuum cleaner plugged in and may only be using 12 amps - and only while the vacuum is on.

Or you may have a kitchen range breaker rated at 50 amps [maximum]. But may only have one stove top burner on and are only using 10 amps.

For getting close to 200 amps, I like to use Thanksgiving as an example. Electric heating may be on in all rooms of the house. The oven and several burners are going as mom cooks up a feast. Grandma is helping in the kitchen using the can opener and microwave or hand mixer. Maybe the clothes dryer is going.

The kids are in their rooms playing electronic games on TV’s.

Dad is in the living room watching TV.

Grandpa and some friends are in the garage tinkering with electric tools.

So that may be a once a year thing that you use so much electricity all at once. And good that your electric system can handle the load.

If you were ever to exceed 200 amps, your main 200 amp breaker would trip. (Note some main electric panels do not have a main breaker, rather may have up to 6 individual smaller breakers which would not exceed 200 amps.)

Also you can have other electric panels in an out building, upstairs, etc. (called a subpanel). Those may only be rated 100 amps and would have a main 100 amp breaker.

You have it right. The power company won’t allow you to increase the capacity of your service if their transformer can’t handle it. The upgrade requires a whole new panel rated for the 200 amps, and the 200 amp main breaker, and new lines run from the street to handle the additional current.

For a service upgrade, you need a new panel and service drop/wires - installed up to current electrical code*. And will need to contact the electric company to see that they can provide additional electricity. They may need to install a higher amperage transformer for your service. And may need to install lager main service wires.

*Note that an older main electrical service may not be up to code. An overhead wire may be too low, over a roof, the panel may be located where it is now not allowed to install, etc. And with a new up to code system, you will probably need two ground rods placed 6 ft. apart - depends on your local electrical inspector/codes. Metal pipes may need to be bonded to the new grounding system.

For modern electrical codes for electrical services, your electric company should have a document called “Electrical Service Requirements”. That says everything you can/can’t do when installing a new electrical service.

And you need an electrical permit - must be inspected and passed before the electric company will connect the new service.

Oh - besides the main breaker, what about the panel is rated for 200 amps? As far as I can tell, the panel is nothing more than the metal housing/conduits, and then the main breaker plus all the individual breakers.

Mostly it is the two big bars of copper alloy inside the panel that have to be rated at 200 amps. The lines from the street come into the panel and attach to those conductors inside the box through the main breaker, and the individual breakers then attach to them. Consider them to be extensions of the wires coming in from the street. If you need higher rated wires from the street, you also needed higher rated conductors inside the box.

I see, thanks1

In my corner of the planet, the power company is responsible for delivering the power to the meter base. After that it is my problem. They will gladly charge me to extend their delivery system if I am past their last pole. They will provide the high voltage wires, fuse, and transformer gratis. I pay for any needed poles and the labor to string it but I don’t own it. At that point anyone else can tap into my wires. If this all exists already or if they installed it, I am responsible for paying and getting installed everything after their transformer.
My house has its own transformer on a pole by the road. Previous owners paid someone (a licensed electrician) to bury the lines in the yard, put in a new meter base, run the wires from there around the side of the house to the new 200A panel in the closet. Power Co, put in the transformer and fuse to upgrade from a 60A service to a 200A service. Power co provides and installs the meter. Before they do that, they do a quick inspection to the new power panel. The installation also needs a state licensed electrician to sign off on the panelboard installation before the meter is installed. I have heard for this area a 200A service is the minimum they will install to a new residential installation or upgrade. I do not know about retrofits. If I wanted to do a panelboard replacement, I can no longer just “pull the meter” like we used to. They have to come out and pull the fuse feeding my transformer.

In addition to the copper bus being able to handle more amps, the 200 amp box is far larger. That old 40 amp main panel is a small panel with probably 6 breaker spaces. Or if it is even older, it might have spaces for 4 or 6 fuses. It’s the kind of panel you would find in a garage today.

The 200 amp panel will typically have 24 to 42 spaces for breakers. They will also be rated for some half size breakers (two breakers in one space). So the panel specs will tell how many spaces, and how many allowable circuits. Some common ones are:

24 space, 42 circuit (18 spaces can be doubled, 6 cannot)

20 spaces, 40 circuits (all of them can be doubled up).

Dennis

Makes sense. So how exactly can you tell what a panel is rated for by visual inspection? If there’s a big label that says, e.g., “125A max” does that necessarily mean the bus and whatever other components are good up to 125A? Barring, of course, the possibility that some unscrupulous person affixed a bogus label on the panel.

Yes, it “should” be pasted on the cover or elsewhere. But if the cover is lost, or the label cannot be read, well…

I also don’t think a 100 amp main breaker will fit in the space for a 60 amp (the more common size for small panels). But you would need to confirm that, I never looked at them from that standpoint.

Dennis

On an older home up grading the main can cause other inspection problems.
The ranch house where I was born had a 60 amp fuse main. The problem my brother was running into was if he changes out the main on his own then the whole electrical system in the house would have to pass inspection. The house had some knob and tube wirring. And it would loose its grandfather. The inspector worked with my brother. He condemned the main. That meant my brother had to change out the main only.

Correct.

Just wanted to emphasize that, if you have 200 A service, it means there’s a 200 A main circuit breaker in the panel. This means that each leg is limited to 200 A.

1. Let’s assume all your loads are 120 VAC. If you have a 200 A panel, then phase A is limited to 200 A and phase B is limited to 200 A. Max power is 1202002 = 48 kW.

2. Let’s assume all your loads are 240 VAC. If you have a 200 A panel, then phase A is limited to 200 A and phase B is limited to 200 A. Max power is 240*200 = 48 kW.

Of course, you have both going on…

“remove” means bypass the fuses and circuit breakers, but yeah if you do that, you can draw more 300 Amps,400 Amps… etc them then you can cause the panel or service cables to get hot and perhaps set fire to something, or melt the wire doing damage due to the melting metal and perhaps electrifying things that shouldn’t be live.

A UK home typically has a 60 to 100 Amp supply fuse, not that every home in the street can draw that much simultaneously. Of course all of it is at 220/240 VAC.

This is giving problems now for people with electric cars who want a fast charge. Even a 16 Amp charger with a 40 Amp shower on a 60 Amp supply would be problematic as you can easily overload the supply by turning the oven or an electric heater on. Very few private houses in the UK have a 3 phase supply and to get over that will take a huge investment.

40 amp shower?

I guess that would wake you up in the morning…