Hacker News Reader

I always forget the size difference between US and UK homes (I assume toomuchtodo is speaking from a US perspective). Here, in my three-bedroom UK house I'm on a 60A service fuse and considering updating to 100A in the future (amusingly, as part of a solar PV / electric vehicle charger install).

I've never heard of a UK house having a larger than 100A service (although I imagine they exist here and there - it's certainly not common).

I'd never heard of a 400 A service until just this discussion (it's common to have 100 A - 200 A), but it's important to keep in mind the voltage differences and that effect on total power:

UK: 100 A x 230 V = 23,00 W

US: 200 A x 120 V = 24,00 W

Edit: I am wrong in my understanding of US power distribution. It's 200 A per leg, which the US has two of. But it seems like the UK may or may not have 380 3 Phase, so the numbers are weird there too. Wrong all around!

Services to the US are at 240V though they just utilize a center tap transformer to allow two different 120v legs. So that 200 amp service is 200 amps at 240V so approximately 48kW. Largely US homes have bigger feeds in because the US has significantly larger homes on average and the prevalence of AC and other higher power usage devices in US homes.

> but it's important to keep in mind the voltage differences and that effect on total power:

> UK: 100 A x 230 V = 23,00 W

> US: 200 A x 120 V = 24,00 W

That's incorrect. The service drop in the US is 220V. It gets stepped down at the main load center to 120V for most of the regular circuits. So it's more like 48000W service in US houses.

Only small correction to that is that load center doesn't step down voltage. The center tapped transformer at the street steps down the voltage to 240V, but then that center tap on the transformer becomes your neutral so you end up with two legs that are 120V from ground/neutral and 240V from leg to leg in your load center.

Thanks for that correction. In retrospect it makes sense, because each circuit breaker isn't functioning as a little transformer.

> The service drop in the US is 220V.

240V. Since we're throwing around numbers, let's be accurate. This is a pet peeve of mine. We've been standardized at 240V since 1967, and it was higher than 220V years before that.

Thanks for the correction about the actual voltage today.

However, it seems like 220V was the standard before that [1], which is why it's still common parlance, referring to the "higher" voltage. Certainly I've heard many people in the trades still refer to it with the older term, even if the circuit is actually 240V.

1. https://en.wikipedia.org/wiki/Mains_electricity#History

The voltage started at 220 way before the 60s, and then increased incrementally over the years, until standardizing at 240V. I don't know when the first bump past 220 happened exactly, and it may not have been simultaneous in all areas. I gather the reason for the standardization was to stop the creep and pick a voltage to stick with for everyone.

The service drop in EU/UK is 380V. The point stands.

That is incorrect. The EU/UK are on 230V at 50Hz at residential service entry. The point does not stand.

This varies.

Houses and apartments in Denmark have 3 phase service. My apartment's main breaker is labelled 40A @ 380V.

I believe the oven and hob make use of it, but I haven't looked myself.

So that 380V would be for 3 phase to a home which is not always the case. There are plenty of homes in Europe that only have single phase to the house which is at 230V.

400V between phases, 230V phase to neutral. Most homes have single phase though.

So how would you run an instant water heater or electric induction stove then? Every apartment and house I've ever lived in had 380V three-phase right to the kitchen, to the bathroom, and to basement rooms (e.g. for prosumer workshop tools).

We don't run an instant water heater. It's all gas or electric boilers.

For the stove I wired one phase to all the burners and the oven. It had one, two or three phase options. They're on a separate circuit with a 16 amp fuse. It's 2200W I believe. The breaker has never tripped.

400V is just not very common for residential in the Eastern Europe, maybe in your country you have instant electric heaters and other powerful appliances. My dad has recently upgraded his house to 400V 3 phase though, although he didn't need it but it's nice to have.

> So how would you run an instant water heater or electric induction stove then? Every apartment and house I've ever lived in had 380V three-phase right to the kitchen,

I run an induction stove on 220V single phase every day here in the US.

Isn't it two phase? AFAIK in the US you have 240V two phase with 180° between them.

The US uses a single, split phase

https://en.wikipedia.org/wiki/Split-phase_electric_power

No, he's right.

It's not about having 400 amps per se but about sizing the wire you put in the ground. Maybe you'll have a 200a main breaker and you'll only ever use 200 amps, etc. - but the hard part was digging and future you or other future yous will be happy that the wire was upsized when it was put in.

Same with conduit. Same with number of conduits.

I can't tell you how many times I have been very pleased with myself that I threw in that extra 3/4 conduit line when we dug that one trench that one time ...

Voltage to residential main electrical service panels in the United States is 240V. Major appliances run on 240V circuits.

So when you install a 400A panel in the US, it's 400A*240V which is 96,000W.

And service in EU is 380V, so the relationship between the numbers remains similar.

That is incorrect. The EU/UK are on 230V at 50Hz at residential service entry.

I'm not sure where in EU you live, but every instant water heater, stove, and many semi-professional workshop devices require 380V. At least in Germany, 380V is standard for such devices and available in every household.

I think you might almost understand how it feels when someone makes gross generalizations across the entire US :).

One thing I keep learning about the EU is ... do not generalize using Germany as the baseline. There are many areas where Germany is the odd one out, not the standard.

3 phase vs single phase depends on which country you're in in the EU.

Isn't this because the UK standard is 230 volts? The US is only 120, so you need almost twice the amps for the same power.

Services to the US are at 240V they just utilize a center tap transformer to allow two different 120v legs. So that 200 amp service is 200 amps at 240V so approximately 48kW.

A friend of mine has 400A of service in the UK in the countryside as it's an old farmhouse and is pretty large even by USA standards.

UK homes run on 230 volts, so each amp is worth double what US amps are worth (running on 115 volts in the US) edit: 115 volts per leg, and US has 2 legs, so it comes out in the wash, surprisingly. UK homes have tiny little service amps!

No. US homes run on 240V, not 120, and not 115 * 2. We provide a center-tap neutral so you can split the single phase 240V if you desire. And we do exactly that for many smaller circuits, including the majority of wall sockets.

> if it's within your means, go to 400A to future proof (EVs, HVAC and hot water heat pumps, induction stove, and other large loads all add up, along with colocated generation of some sort

I have all of these on 200A with amps to spare. But I have a small house. I suppose if I had multiple EVs, dryers, or heat pumps, or 3000sqft it would be a different story.

Again, see above - it's not about 400 amps per se ... it's about putting in bigger wire because we can't predict the future.

It's spending a small additional amount now (on wire) to avoid an enormous expense (trench digging) in the future.

Oh, and you know that 3" conduit required for the 400amp ? Make it 4".

Oh, and you know that trench you just dug ? Throw in double 1.5" and double 3/4 conduits right in there with it.

Oh and you know that first two feet of dirt you filled in ? Now throw two more 3/4 conduits on top of that because you never know when a common carrier on that same pole will have fiber up on it ...

Future you will be very happy you did.

> Future you will be very happy you did.

The future could also look like large batteries on-site that charge slowly, and then provide power at high amperage when needed, like slowly compressing a spring, then suddenly releasing it.

This is already what Electrify America and Freewire (https://freewiretech.com/) are doing with EV Fast chargers when the electric utility can't provide a higher power connection in a reasonable time-frame. As battery prices drop, that could be a viable way to power heavy home appliances.

This is double-great advice. It's completely obvious once mentioned but not something that may have occurred of the top of ones head. Thank-you for posting.

It's strange because 400a service will probably NOT ever be needed, but the cost difference from 100-200 and 100-400 is basically nothing.

You can also get a separate meter installed instead or alongside, this can be useful it the property could be dual purpose (think: duplex, house + machine shop, etc). This can increase costs because of double baseline but it can also reduce costs because of double "low tier" - depends on the market.

Good advice. I just did the 400 amp upgrade. Our 3200 sq ft house was still on 150 amp service from the 1980s, and going to 200 amps just didn’t seem to add much capacity relative to the cost. Was about $12K to go to 400 amps with two 200 amp panels.