I want to pay my neighbor back! How can I measure electricity usage?

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mahyar

Active member
Joined
Feb 20, 2021
Messages
27
My lovely neighbor is giving me access to his outdoor outlet for trickle charging my Leaf. Is there a simple way to measure how much electricity I consume each month? I know I can pay attention to before and after percentage in leaf but I'm looking for a more automated way (and also obviously there will be a loss while charging). Something like a smart plug which can withstand trickle charging current. A plus would be something the neighbor also can see.
 
https://www.amazon.com/P3-P4400-Electricity-Usage-Monitor/dp/B00009MDBU?th=1

There are competing brands if you care to shop
 
Although I'm a huge fan of Kill-A-Watt (have had one for ages and it's a great gadget), I would don't recommend it for continuous large loads like charging at 12 amps @ 120 volts. See https://mynissanleaf.com/viewtopic.php?p=173537 and earlier posts there (e.g. https://mynissanleaf.com/viewtopic.php?p=173354#p173354).

I'd be ok w/hooking a large load for a few minutes to see how much something is drawing but no longer than that. For something that's just a few hundreds watts, it's not an issue but 1440 watts? Nope.
 
SageBrush said:
https://www.amazon.com/P3-P4400-Electricity-Usage-Monitor/dp/B00009MDBU?th=1

There are competing brands if you care to shop

I can search. Can all of them withstand the 12A current?
 
cwerdna said:
Although I'm a huge fan of Kill-A-Watt (have had one for ages and it's a great gadget), I would don't recommend it for continuous large loads like charging at 12 amps @ 120 volts. See https://mynissanleaf.com/viewtopic.php?p=173537 and earlier posts there (e.g. https://mynissanleaf.com/viewtopic.php?p=173354#p173354).

I'd be ok w/hooking a large load for a few minutes to see how much something is drawing but no longer than that. For something that's just a few hundreds watts, it's not an issue but 1440 watts? Nope.

The conclusion is smart plugs would melt?
 
They might. I don't know which ones can withstand such a load.

You might be better off just estimating if you know how long the car will be pulling power for. For virtually the entire time it's charging, it will be pulling 1.44 kW from the wall, so each hour, 1.44 kWh came out of the wall.

I don't know if the bounces I mentioned at https://www.mynissanleaf.com/viewtopic.php?p=521892#p521892 happen at 120 volts. I can only see graphs on my work's L2 208 volt EVSEs (e.g. https://www.mynissanleaf.com/viewtopic.php?p=490435#p490435).
 
I recommend just using 1.44 kW times the number of hours charging so 10 hours would be 14.4 kWh, as an example. There is very little tapering when charging at 120 volts so the error would be minimal. The only time I charge at 120 volts is when I use my car as a heavy load to exercise my Honda generator. I have tested a "kill-a-watt" unit to confirm the output of the generator, but would not recommend using it on a continuous basis because it does get warm.
 
The Kill-A-Watt meter is rated for a max amperage of 15A and the stock EVSE draws 12A. So, it should be fine for use with the stock EVSE.
 
If your neighbor has a smart (electric) meter, their utility might let them view the power usage of their house hour by hour. PG&E (mine) does. It shows me how many kWh were used each hour.

So, one can make an educated guess as to within which hours charging started and when it ended. Each whole hour where it's pulling full power should show ~1.44 kWh more usage than what it does normally at that time. And, the partial hours at the beginning and end will be elevated by not the full 1.44 kWh.
 
alozzy said:
The Kill-A-Watt meter is rated for a max amperage of 15A and the stock EVSE draws 12A. So, it should be fine for use with the stock EVSE.
See my reply. Folks have had theirs melt and also their build quality is variable w/multiple revisions happening along the way.
 
cwerdna said:
If your neighbor has a smart (electric) meter, their utility might let them view the power usage of their house hour by hour. PG&E (mine) does. It shows me how many kWh were used each hour.

So, one can make an educated guess as to within which hours charging started and when it ended. Each whole hour where it's pulling full power should show ~1.44 kWh more usage than what it does normally at that time. And, the partial hours at the beginning and end will be elevated by not the full 1.44 kWh.

I'm actually willing to pay 1.44kWh or 50% more as it is cheap here in TX (10cent/kWh after all fees). It 1.44kwh will be like 20$ per month for me and 5% more is 30$.
 
cwerdna said:
alozzy said:
The Kill-A-Watt meter is rated for a max amperage of 15A and the stock EVSE draws 12A. So, it should be fine for use with the stock EVSE.
See my reply. Folks have had theirs melt and also their build quality is variable w/multiple revisions happening along the way.

You are right. There are seems to be many reviews in amazon regarding that:
https://www.amazon.com/gp/customer-reviews/R2QN1GELH6K4DI
 
cwerdna said:
Although I'm a huge fan of Kill-A-Watt (have had one for ages and it's a great gadget), I would don't recommend it for continuous large loads like charging at 12 amps @ 120 volts. See https://mynissanleaf.com/viewtopic.php?p=173537 and earlier posts there (e.g. https://mynissanleaf.com/viewtopic.php?p=173354#p173354).

I'd be ok w/hooking a large load for a few minutes to see how much something is drawing but no longer than that. For something that's just a few hundreds watts, it's not an issue but 1440 watts? Nope.
Totally agree with this and I also have a couple Kill-a-watts
I purchased and installed one of these for someone several years back and it also worked for 240v. It's more meant for permanent or hardwired use, but could probably be wired into a plug. As the power doesn't actually go through it, you wouldn't have to worry about it getting warm like a Kill-a-watt. Looks like the one I got is no longer available at Amazon but this one looks similar, mine worked very well.

https://www.amazon.com/HiLetgo-Multimeter-PZEM-061-Voltmeter-Transformer/dp/B079JNY5VD/ref=dp_prsubs_1?pd_rd_i=B079JNY5VD&psc=1
 
alozzy said:
Sorry for the bad advice, I didn't realize that Kill-A-Watt false advertise their amperage rating.
I wouldn't day so much false advertising but if something is rated for 15a its probably more be meant for 15a for a short period of time, not continuous use like an EVSE. Similar to a 15a circuit might be OK for 15a shorter periods of time but not continuous use. In the case of a Kill-a-watt I "personally" wouldn't exceed maybe 10a continuous, but I'm probably on the conservative side, it "should" be able to handle 13a continuous but I've tried that and things get warmer than I'm comfortable with.
I do know a 15a kill-a-watt does NOT like more than 15a, even for a short period of time. I once tried it on a 16a load and the display freaked out, blinking off and on. I unplugged it shortly after I noticed the issue but unfortunately, it fried the kill-a-watt, after that, it never read correctly :(
 
Back to paying for electricity ...
Metering is a PITA. I would off to pay the local rate for a kWh every 3 miles on the odometer and call it a day. Keep a log of your odometer and update/pay once a month.

If OP is an aggressive, lousy driver than up the payment to a kWh every 2.5 miles.
 
alozzy said:
Sorry for the bad advice, I didn't realize that Kill-A-Watt false advertise their amperage rating.

I've used a Kill-A-Watt on at 12 amps for weeks.

But I first monitored the temperature of the unit for a few hours.
 
I reasoned that 12A was only 80% of the claimed 15A max load, so the Kill-A-Watt should handle that continuously. Sounds like there's been mixed experience with that.
 
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