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

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.

Ubiquiti mFI mPower Project – Part 1

This year I upgraded the home monitoring suite in my house from a Wattson to a Splunk dashboard running on a tablet in the kitchen. The primary reason for doing this was that after getting the Tesla Powerwall, Wattson no longer was able to correctly state how much power was being imported/exported from the home until the battery was completely charged. The downside of getting rid of Wattson was that we relied on the Optiplugs to run the immersion and a radiator when there was excess power being sent to the grid. So I needed another solution to running the immersion on the rare days when the Powerwall will be completely charged and we’re exporting to the grid.

After a fair amount of time searching for a wireless plug with an API, I found the following plug https://wifiplug.co.uk/ that ticked all the boxes, but being the little bit paranoid I am, I didn’t really want a plug that could theorietically be controlled by anyone from the internet. Also, if that company went bust, how would I control the plug without their API gateway?

I then spent another handful of hours searching and came across the following blog https://blog.linitx.com/ubiquiti-mfi-mpower/ which happened to use a wifi plug that doesn’t rely on an internet connection and is from the same company that I use for my WiFi access points! The only problem is that unlike the wifiplug, this one doesn’t have an official API and there isn’t a UK plug version… But what the heck, at least it’d be an interesting project!

So I bought the European single socket version from wifi-stock.co.uk/. The next day I got a call from wifi-stock to check “I hand’t made a mistake and that I did realise it wasn’t a UK power socket” – that was nice and a good idea! 🙂

I also needed a UK to European adaptor and a European to UK adaptor to be able to use it in a UK socket and power a UK device. This makes the plug stick out quite far from the socket, but it is secure and doesn’t drop over time.

A couple of days later my plug arrived and I set about logging into the device as mentioned on the blog using ssh. That was suprisingly easy as it uses the default username and password that’s used on some of the other Ubiquiti devices – username:ubnt, password:ubnt. I spent a couple of hours poking around on the file system, making the lights blink on and off and tested out that it was possible to turn the plug on and off by echoing 1/0 to the relay

echo 1 > /proc/power/relay1
echo 0 > /proc/power/relay1

I also found the code for the web GUI on the plug /usr/www/mfi/power.cgi (the code behind this: http:///mfi/power.cgi). And that got me thinking…

I was originally going to control the plug from my server via the home monitoring application using ssh, but that means the Java app will have to invoke the ssh command and I’d prefer to have an API on the plug that I could call. I could write another cgi file like the power.cgi file, remove the session aspect and control the plug as Ubiquiti have done, but why bother! Ubiquiti has done all the leg work – I can just use their web app! 🙂

So I began playing with the power GUI and found that it was making POST and GET requests from the GUI to http:///sensors/1/ to fetch the current status and turn the plug on and off. Well that’s easy to control! After a bit of experimentation, these are the four curl commands I need.


You will get an AIROS_SESSIONID back which needs to be put in as a cookie header in the following curl requests.

Get plug data

curl -v \
    http://<device ip>/sensors/1/ \
    -H "Cookie: AIROS_SESSIONID=015152b0143a0267f8f0ae30fcb42f6f"

Switch the plug off

curl -v \
    -X PUT \
    http://<device ip>/sensors/1/ \
    -H "Cookie: AIROS_SESSIONID=015152b0143a0267f8f0ae30fcb42f6f" \
    -H "Content-Type: application/x-www-form-urlencoded" \
    -d "output=0"

Switch the plug on

curl -v \
    -X PUT \
    http://<device ip>/sensors/1/ \
    -H "Cookie: AIROS_SESSIONID=015152b0143a0267f8f0ae30fcb42f6f" \
    -H "Content-Type: application/x-www-form-urlencoded" \
    -d "output=1"

Output and enabled on

The above is only controlling the output field but on the GUI you will notice there are two fields, output and enabled. Switching enabled on gives stats about the plugs energy usage but it’s not required to control the device.

To switch the plug on with output and enabled on, simply run

curl -v \
    -X PUT \
    http://<device ip>/sensors/1/ \
    -H "Cookie: AIROS_SESSIONID=015152b0143a0267f8f0ae30fcb42f6f" \
    -H "Content-Type: application/x-www-form-urlencoded" \
    -d "output=1&enabled=1"

If you then request the plug data, you would get something similar to the following response:

curl -v \
    http://<device ip>/sensors/1/ \
    -H "Cookie: AIROS_SESSIONID=015152b0143a0267f8f0ae30fcb42f6f"


In the next part I’ll go through how I controled the plug from Java using the APIs above.