Comparing NorthAmerican kWh and European kWh

harriethijssen · 30 December 2018 01:46

Hi All,
My goal is to figure out what the big energy eaters are in my house. I grew up in The Netherlands and moved to Canada when I was 25. I have now lived in Canada more than I lived in The Netherlands so that kinda shows my age I guess.

When I was talking to my brother “back home” (NL) we started talking about energy bills. We compared bills, and his kWh usage was approximately one fifth of my kWh usage. In case that this was a fluke, I also compared with my brother-in-law: similar results. I then also compared my usage locally, and my bill is a bit larger since my home is larger, but not by a factor 4 to 6 (see below)
That led me to believe that a European kWh is different than a North America kWh
I therefor decided to do some investigation, and based on findings want to inquire with my local electric utility.

A: brother (3759 kWh/year, 313kWh/month):
My brother lives in a regular home (row house with neighbours attached on either side). It’s just him and his wife. Home is heated by natural gas, hot water heated by gas (“geiser”/on demand) as well. Stove is natural gas

B: brother-in-law (5211 kWh/year, 434 kWh/month)
My brother lives in a regular home (row house with neighbours attached on either side). It’s just him and his wife. Home is heated by natural gas, hot water heated by gas (“geiser”/on demand) as well. Stove is electric/induction

C: me:(21669 kWh/year, 1806 kWh/month)
I live in a detached (larger home), my wife, myself and a grand daughter. Home is exclusively heated by wood furnace (electric fan blows heated air through ducts), hot water is heated electric (hot water tank/boiler). Stove is electric.

C (1806kWh/month)	A (313kWh/month)      B (434 kWh/month)
=================       ================      =================
hot water (elec)	hot water (gas)       hot water (gas)
electric stove		stove (gas)           induction stove
heat (wood furnace)     heat (gas)	      heat (gas)

Factor			21669/3759 = 5.8      21669/5211 = 4.2

I can understand a factor 2 -3 (120V vs. 240V), but factor 4 up to almost 6 I cannot understand.

My plan is now to apply a number of CurrentTransformers with varying Amp ratings to find out where these kWh are going. I will be using ESP32 with (18 AnalogDigital inputs, 12 bit, 0-3.3V)

which CT’s should I get: current or voltage (xxA/1V or xxA/50mA)?
I did some trial/error to determine calibration (using a handheld Amp meter) and ended up with 13.7 (SCT-013 15A/1V). Does that seem like a normal value? I used 10kOhm to split the 3.3V.

Background

I’m not sure whether you’re aware of a “typical” residential electric install in North America (if so skip this section).
Transformer usually has a few (1-8?) customers (depending on expected demand), single phase service drop to the house to a 200A or 400A panel, 120/240V (A and B wire plus Neutral. A-neutral: 120V, B-neutral: 120V, A-B: 240V). NL distribution mainly underground, Transformer typically feeds many services (20+ ?).

In my house I have a “main” panel and 3 “pony” (sub-) panels. The main panel (400A) can accommodate 40 “full” size breakers (120V), each breaker ranging from 15-40A. A “full” size breaker can be replaced by 2 breakers (one housing), same Amp ranges as full size to potentially have double (80) circuits. For 240V loads (clothes dryer, electric stove, etc.) a breaker is “bridged” and providing both A- and B-wire, sometimes neutral for 120V circuit. I have a 40A sub panel in the basement, another 100A subpanel in attached garage and a small 40A panel next to the main panel that has 16 “old” (screw in type) fuses.
Additionally, next to the main panel is “double-pole/double-throw” panel for external generator hookup (well water).
The house was built approx 40 years ago by an electrical contractor (commercial I think) so many hookups are not totally “up to code”…

Edit - formatted post for readability. BT - moderator

Robert.Wall · 30 December 2018 02:32

I’m afraid not - they are both the same.
So you must look at lifestyle, and differences in the size and construction of the houses, and climate, to explain the differences.

You have more flexibility with a true current transformer - you can choose the value of burden resistor so that, at the cost of an increase in the errors, you can increase the sensitivity (but only up to a point - e.g. our emonTx has one “high sensitivity” input scaled to ~18 A full scale, but using a 100 A : 50 mA c.t.

But a 1 V output should offer slightly better accuracy, as it will be factory-calibrated, so won’t have the uncertainty in the burden resistor value to be taken into account.

Don’t have a c.t. that has a rated current that is too small. 15 A (on a 120 V supply) represents a load of less than 2 kW. If you will only measure light-current circuits, that’s OK. My bet is you’ll have a water heating load that’s significantly bigger than that. You also need to take inrush into account. If your biggest breaker is 40 A, you should be looking at c.t’s rated somewhere near this. You can safely say that a half-decent 50 A c.t. will work comfortably down to around 1 A and with reasonable accuracy, and we find that even our ‘economical’ SCT-013-000, although only spec’d down to 10 A, with a 10-bit ADC performs reasonably down to around 1 A, when accuracy starts to suffer.

I don’t know how you got to 13.7 A, but if you’re using 1.8 MWh/month, that represents a constant, continuous load of around 2.5 kW, which is 20 A at 120 V - spread across a few circuits of course. That leads me to suspect that your estimate will be significantly low for at least a few of your circuits.

We have many users, and two of my moderator colleagues, who are in N.America. So even I have a reasonable idea of what you have.

Bill.Thomson · 30 December 2018 05:27

I’m in the US, so I’m not sure just how closely your appliances parallel those used in the US.

Your air handler motor may be something of a surprise. I know I sure was when I found out how much
power one of mine uses. I have two of them. One, a newer unit uses 160 Watts. the other, an older unit,
uses 360 Watts.

A typical wather heater immersion element is usually 4500 or 5500 Watts.
Depending on where your water heater is located, how much use it sees, etc, you’ll likely find it’s near the
top of the list for energy comsumers. But it still shouldn’t be outrageous. Here’s a graph of energy consumption of one of my 40 Gallon units for the last 30 days: (I have two of them, too)

The electric stove I have has four heating elements. Two small and two large.
The small elements use ~3300 Watts, the large elements, ~5500 Watts.

As Robert mentioned, you’ll likely find lifestyle to be a big factor.
I have a 2400 SF home (all electric) and my energy use is ~900 kWh per month.
But, like your brother and brother-in-law, I have no children at home.

harriethijssen · 30 December 2018 20:06

Well, that bites. I added some pics and links, but when posting I got: “new users can only have 3 pics and 2 links”… I manually edited out some pics.

Approximately 60% (pure guess) of my circuits are on a 15A breaker, that’s why I already purchased a few SCT-013 15A/1V ct’s. I figured that those would give me most accuracy on those circuits protected by a 15A breaker.

Not sure where you read “…13.7 A…”. I did use a calibration factor of 13.7 in the API to get it to return a similar Amp number as on my handheld multimeter (which also uses a ct).
The calibration factor of 13.7 I use is from the Arduino example:
emon1.current(1, 111.1); // Current: input pin, calibration. Emonlib example on Github
I measured the fan on my wood furnace with multimeter, roughly 6.4A.

In order to get the example to return a similar number, I had to use a calibration factor of 13.7 (through trial and error approach)

I have a New Mac solid fuel (wood) furnace as in the link.

Spec sheet says 5.4A, 120V (650W)

I run the fan continuously in the winter, not in the summer. It does have a thermostat so it comes on only when the furnace is “hot” enough, which you can override to run continuously (which I did). I’m worried that frequently starting the fan may kill the motor quicker. It also has a blower that runs approximately 12h/day:

Fuse panel

Pony panel in garage

Pony in basement. I think this is a recycled “3-Wire” panel (not sure about the exact name). Every 3rd slot is empty since I only have 2 hot wires coming to the house.

Main panel,fuse-pony and “double-throw” panel for generator hookup so the well keeps working in case of power-outage (not hooked up yet).

I’m going to replace the water heater. It currently is a rented one (from electric utility) but is old. They normally will replace with a newer one, but not in my case since it is not plumbed in to code…
I’m currently considering buying an on demand tankless water heater (27kW). It has 3 x 9kW heaters on 3 x 40A breakers. The location is approx 10’ from the main panel so I need to get 30’ of 8/2 (AWG size 8, 2 wires) wire. I’m hoping to get some savings on that unit.

harriethijssen · 30 December 2018 23:49

@Bill.Thomson: Thanks for the edits!

Few questions:

is there a way to add tables to posts? (I guess not, else you would have changed my post). I did not see a place to change the font to courier (monospacing). Not that I’m complaining: I think the platform (the software) this forum is built on is great!
pictures are important to explain things. I guess I don’t understand the rationale behind the rule where “newbies” like me cannot add more than 3 pictures (and 2 links).

Thanks,
Harrie

Robert.Wall · 31 December 2018 00:52

The system thinks there’s a good chance you’re a spammer. I don’t, so you can now.

Yes, two to be precise: I paste straight from LibreOffice Calc:

Current	No.1 22Ω burden
0.010	0.013
0.020	0.025
0.051	0.063
0.101	0.126

Or you can do it by hand by inserting vertical bars - you need the line with hyphens (‘-’) following the header for it to recognise that the whole thing is a table:

|Current|No.1 22Ω burden|
|---|---|
|0.010|0.013|

etc.

which should yield the following output:

Current	No.1 22Ω burden
0.010	0.013