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Tesla Powerwall – Early Differences In Grid Consumption

It’s been just over 5 months since we had our Tesla Powerwall installed and I thought I’d give an early update on the difference it’s made to our grid consumption so far. It is still early days and I will provide another update once I have a few more readings – probably late next year.

Our electricity billing periods are:

  • Jan 16th
  • April 16th
  • July 16th
  • October 16th

Our Tesla Powerwall was installed on June 1st 2018, which means the July bill should have showed some difference in kWh grid consumption (especially given the lovely summer we had this year!) even though it was a partial month of having the Powerwall, whereas the October bill was a complete month of having the Powerwall in operation.

I think the graph says it all! Even on the July bill, we saved 266* kWh or a 37.5% drop and on the October bill we saved a massive 560* kWh or 70.3% drop!

I just wish we’d had the battery installed 6 weeks earlier to benefit even more from the fantastic summer weather we had this year! 🙂

* based on the average of units consumed 2013 to 2017

For those interested in the figures:

July October
2013 663 814
2014 694 778
2015 783 847
2016 724 792
2017 681 754
2018 443 237
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Nissan Leaf 2.zero 8000 miles update

I’ve now had my car just short of 6 months and have clocked up 8000 miles so I thought I’d give an update.

Money I’ve saved

I’ve spent a grand total of £23.42 on fuel since getting the car 😀 Compared to £50 every 5 days, this is quite a significant saving! Having said that… the car cost a small fortune, so it’ll be a while until I’ve saved enough on fuel to justify the cost of the car.

Long journeys

The two longest journeys I’ve completed are 120 miles driving down to Stratford to see the atletics and 127 miles to and from work + a trip out during the weekend.

The 120 miles to Stratford was the first long range journey I made. The car was fully charged when leaving home and I’d made a note of where to top up on the way home at a rapid Ecotricity if necessary. We went A1, M25, M11, with most of the A1 and M25 and M11 at a constant 63mph using adaptive cruse control. After the M11 the drive was a lot slower as we seemed to take a wrong turning so the majority of the drive from the M11 to Stratford was <30 mph.

On the way home, we had a slightly better route out of Stratford to the M11, but then found the M25 was shut before the A1, so took the M11 home. It was quite late so I decided to get home a little quicker by doing 70mph *cough* all the way up the M11 to our junction at Duxford. This cost us quite a bit on the consumption front but was a good test for the car and gave me great confidence in being able to get 120 miles out of the battery when not exactly driving conservatively. We arrived home with 120 miles on the clock + 20% left in the battery 🙂

The second slightly longer trip of 127 miles was a normal commute to and from work + a trip out to Yew Tree Alpacas. I’d driven home from work doing 70mph the whole way home as I was late. I got back to work three days later with 16% left in the battery. I was yet again impressed with the range given I wasn’t exactly driving conservatively!

Weird things I’ve found out

You can’t leave the driver’s door slightly ajar when moving the car! It jumps out of drive/reverse into park… This can also happen if you look around when reversing and the amount of pressure on the drivers seat detects no driver in the seat as mentioned by someone else in this thread I started on SpeakEV https://www.speakev.com/threads/jumped-out-of-gear-4-times-reversing-off-drive.124960/.

Scary moments!

I really like the adaptive cruise control, but you have to be aware at all times when it might “glitch”…

On the way to Stratford I was behind a lorry which was going a little slow at 55mph. I was aware there was going to be a gap in the traffic on my right after the car on my right had finished going past me, so I indicated right to pull into the lane and began to move (after the car on my right was about 1 cars length in front of me). Unfortunately the lorry in front of me had also moved into another lane and the adaptive cruise control noticed the lack of lorry and sped back up to 63mph just at the same moment I was moving into the right hand lane!! The car shot forward so fast I really don’t know how we missed the car in the right hand lane, but luckily I’d put my foot on the break to avoid the impact in front. That was a really scary moment! I realised immediately afterwards that I should have taken the car out of adaptive cruise control mode but it’s just one of those things that you can forget when moving lanes…

I’ve had quite a few of the… car in front goes into slip road on left, but adaptive cruise control is still tracking the car and when the car on the slip road slows down from 60mph to 10mph so does my car!! :/ <– not impressed face

Things I really like about the car

The 100% torque is really handy (if a little addictive)! Driving along at 60 and being able to put your foot down going to go around a lorry, not having to change down a gear to get the car to move is fantastic 🙂

I really like the drivers dashboard. There’s a massive range of displays to choose from (even if I mainly stick with the drive computer page) and it’s modern looking. I also particularly like the satnav popup on the drivers dashboard when using the Nissan satnav.

The blindspot warning is great – can’t see why all new cars don’t have this feature.

I think it takes less time each day to plug and unplug from the charge point than it did to queue and then fill up at the petrol station!

Things I’m not impressed/happy with…

I got really annoyed with the finance company. I made a large lump sum payment towards my loan and after 5 days of checking every day, the payment hadn’t registered in my online account portal. I emailed to find out if the payment had been received and when it would appear on the account and the response I got back said it could take up to the end of the month to show on my account!!

I got really angry with the response from RCI as it should not take more than 2 working days to process any payment and make it show on my account! How do I know whether I’m not being charged interest on the portion of money I’ve paid off? So I paid off the loan less than 30 days later.  I’d always planned to pay it off early (I’ve never kept a loan till the end of the agreement), but I kept it for less than 2 months in the end.

I’m finding the drivers seat gives me pains in my left leg in two points. It appears to be where the side wall of the seat contacts with my leg and there doesn’t appear to be any way to sit in the seat to avoid this. This problem is still ongoing.

Electric car charing points don’t tend to have a roof like petrol stations do, so if it’s raining and you need to plug in, you’re going to get wet 🙁  (Haha – my colleagues do laugh at this one!)

Would I buy the car again?

I’m torn on this…

Electric cars are definately the future and I won’t be going back to an ICE vehicle. However, whether I’d choose a Nissan again given the problem with the finance company, the lack of help from the dealer with the seat + the bits not working on the car when I got it – I’m not sure I would go Nissan again… That said, perhaps it was the dealer chain I bought the car from? I went to Letchworth recently to use their free charging point and the sales guy who moved the demonstrator out of the charge point spot was really helpful (helped me get my car on charge when I had issues with the charge point) + the service guy who came to look at the problem I had with one of the interior panels sorted a problem out there and then!

I had second thoughts on my car after getting it, thinking I’d trade it in for another car as soon as the 2019 Hyundai or KIA electric vehicle was released but I’ve decided to keep this one 🙂 So I guess that says it all… despite the problems, I’ve become attached to it.

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Home Monitoring Re-Write Number Four and the HTTP Status Code 499 Errors

As previously mentioned in the home monitoring re-write number four post, I have a number of Arduinos around the house that collect data and send the data using an HTTP POST to the home monitoring application. During the upgrade of the home monitoring stack, I decided to introduce Nginx to proxy the requests that go to the home monitoring application for visibility and also to do a little bit of url re-writing.

Before Nginx was introduced I had Arduino’s making POST requests to a set of PHP files which received the request, added a timestamp and a header and re-posted the data to the home monitoring application directly. That process was only slightly changed to instead of POST directly to the home monitoring application, POST to Nginx which would proxy the home monitoring endpoint.

I noticed a few weeks after this introduction of the new stack that the grid import figures seemed rather low (factor of 10!) compared to the units that the import meter was reporting and found that the majority of POST requests from the Arduinos were getting stopped mid flight between Nginx and the home monitoring application with a 499 HTTP status code, e.g.

192.168.XXX.XXX - - [27/Aug/2018:07:04:11 +0000] "POST /meter HTTP/1.1" 499 0 "-" "-" "-"
192.168.XXX.XXX - - [27/Aug/2018:07:05:11 +0000] "POST /meter HTTP/1.1" 499 0 "-" "-" "-"
192.168.XXX.XXX - - [27/Aug/2018:07:06:11 +0000] "POST /meter HTTP/1.1" 499 0 "-" "-" "-"
192.168.XXX.XXX - - [27/Aug/2018:07:08:11 +0000] "POST /meter HTTP/1.1" 499 0 "-" "-" "-"
192.168.XXX.XXX - - [27/Aug/2018:07:10:11 +0000] "POST /meter HTTP/1.1" 499 0 "-" "-" "-"

After a small bit of googling and checking the code used on the Arduinos it was obvious that the previous method of sending data would need to change a little to work with Nginx acting as a proxy. As mentioned in this stackoverflow answer “HTTP 499 in Nginx means that the client closed the connection before the server answered the request” the Arduino isn’t waiting for the response from the server and is closing the connection too early – therefore the data didn’t reach the home monitoring application. In the previous setup the Arduino could fire the data and forget (close the connection) immediately after sending the request as it wasn’t interested in the response.

To fix this, all I needed to do was introduce a small wait after sending the data to reduce the number of 499’s. The code now reads, establish a connection, send data, wait 15ms, close connection – or for those that want to see the full code:

  String postData = getPostData();

  if (pompeiiClient.connect(pompeii, pompeiiPort)) {
    Serial.println("connected to pompeii");
    // Make a HTTP request:
    pompeiiClient.println("POST " + String(pompeiiService) + " HTTP/1.1");
    pompeiiClient.println("Host: " + String(pompeii) + ":" + pompeiiPort);
    pompeiiClient.println("Content-Type: application/json");
    pompeiiClient.println("Content-Length: " + String(postData.length()));
    pompeiiClient.println("Pragma: no-cache");
    pompeiiClient.println("Cache-Control: no-cache");
    pompeiiClient.println("Connection: close");
    pompeiiClient.println();

    pompeiiClient.println(postData);
    pompeiiClient.println();

    delay(httpRequestDelay);
    pompeiiClient.stop();
    pompeiiClient.flush();
    Serial.println("Called pompeii");
  }