Tesla Powerwall II

Tesla Powerwall II

First the good news – We finally had our Powerwall installed by Totnes Energy at the end of May 2018 following a number of delivery and shipping delays from Tesla.

We have a 5.9 kW solar array which was recently installed by Totnes Energy. I also run a 30 kW Nissan leaf. Therefore the idea of the purchase of a Tesla Powerwall II was to capture and use all the energy I can from the roof for use overnight to power the house and charge the car where possible.

We have just run the system for the first full month in June 2018 and I thought I would record some statistics below for readers to consider if they too are thinking of investing around £6000 in a Tesla Powerwall.

I did not install this system purely on costs terms. I wanted to power the house and car where possible with Free Clean Energy that I had generated myself and not some Dirty Energy generated from coal or oil power stations thus reducing pollution and my carbon footprint.

Below you see the installed battery which has a usable capacity of around 13.75 kWh. It is quite slim and sits on the back garage wall.

All these images are gathered from one day – 28th May 2018.

The screen capture below is from the Tesla App on my mobile phone.

It shows that at 0937 am the battery was 84% full and discharging. That is because I had just plugged in my Nissan Leaf to charge.

The below image is a screen shot from the Nissan Leaf app on my mobile phone.

At 0922 the leaf was plugged in. Its battery level was 34% of its 30 kWh capacity at this time.

It was on a fast charge setting from my Zappi Car Charger and charging at 6.5 kW per hour.

The below image is a screen shot from my mobile phone of the Solaredge Monitoring app. At 0937 it shows the solar panels were generating 4.18 kW

The solar panels had just started generating properly at 4.18 kW even that early in the morning on what would turn out to be a good sunny day.

 

During the day as well as the car on fast charge the house also consumed energy for the washing machine, dishwasher and oven all of which were switched on at various times in the day.

At one time the house was drawing over 9kWh as the fast charger was on and the oven and the dishwasher , but between the solar and the discharge from the Tesla nothing was imported from the grid!!!

The day remained sunny and by 1522 the Leaf had fully charged from Free Clean Solar Energy = another 100 plus free miles with zero pollution on our roads.

According to the display on the Zappi Car Charger the leaf had taken just over 20 kW at fast charge rate of 6.5kWh

A short while later in the afternoon the Tesla was nearly full…..

 

Late afternoon the same day the Tesla Powerwall was at 100% – the Nissan Leaf  was fully charged – The dishwasher and washing machine done – the domestic water heated by the solar Iboost with the nett result of 98% self consumption and only 0.48 kW exported and 0.72 Imported.

This very small import figure being the only minor blot on an otherwise perfect solar powered day.

 

Now the Bad News

That import figure has shown that despite having the battery the system as it is set up it is still drawing small amounts of energy from the grid when it should not be.

There are other issues occurring such as the Iboost cutting in at night for a nano second and sometimes longer when there is no solar production. I have produced a very short video which captures these anomalies.

The Tesla app shows the battery discharging to the house whilst the smart meter lurches between exporting and then importing electricity to the house and on top of that the Iboost keeps trying to cut in.

This problem is currently being researched by Tesla & Totnes Energy

 

The other major draw back for me is that Western Power & Distribution have restricted the export from my supply to 2kW down from its previous 5kW.

This is a major blow to returns from the Feed In Tariff. On a good day as the one shown above I have used up all the energy I have generated.

Below is what happens when the Tesla fills up early and I do not have to charge the car. The green colour on the chart shows the export of electricity. If you look at the sqiggly black arrows all that white area between the two blue peaks shows where the generation was throttled back to 2 kW for export. I cannot understand why WPD would want to stop this generation going back into the grid for others to use – It is a waste of energy!

Conclusion

Despite all of this bad news I can report the battery is saving money and allowing me to use more energy – 95% Self Consumption.

For the month of June 2018 my solar panels generated  634.79 kWh of electricity

I consumed just 495.58 kWh of that electricity

I exported 164.43 kWh

But due to the anomaly with the Tesla Powerwall I did import 25.22 kWh

Having just read both my Gas and Electric meters to update BULB my energy supplier I can confirm my total usage for the month as 22 kWh gas and 25 kWh electric.

My current BULB Tariff is below

Total energy spend

.64p gas

£3.45 electric plus 2 x 7.36 standing charges making a total bill to BULB of £18.82

Less Feed In Tariff for the export of 164 kWh @ 0.07 = £11.48 income

True Cost of Energy for the month of June 2018 is therefore just £7.34

For that I have run the whole house and the Nissan Leaf app shows I have driven 548.7 miles during the month on “Free Clean Energy“

Update to the Tesla Powerwall Problem With Solar IBoost

After much conversation between installer, Iboost and Tesla it would seem that it is a known issue that the Tesla will not work well with the Iboost on some installations. It would appear that the issue sits with the way the Iboost monitors the export and incorrectly decides to cut in.

I spoke with the Sales Director of Iboost on the 12th July 2018, Teresa Auciello. She confirmed it was an issue with the Iboost. They were having difficulty with the Tesla technical team in getting to grips with the issue which would involve new software being written for the Iboost and then tested fully before role out. I have to say her frank statement of the issue was very refreshing.

The only solution for me in the short term was the offer by my installer to replace the Iboost with an eddi from Myenergi. This is supposed to work well with the Tesla and as I have a zappi by the same company hopefully this should resolve the issue for me. I am therefore awaiting delivery of said eddi. I will update the result when known.

Update 09/08/2018

Well the eddi from myenergi has been installed. It took many hours to configure and get it working properly but here is the proof below. The eddi is so much quieter than the Iboost and looks a much better quality piece of equipment. There has also been a slight reduction in the constant draw from the grid so clearly the Iboost was in part a contributing factor.

And here is a screenshot from my BULB account, you can see what an impact the Tesla Battery has had on consumption.

Tesla Powerwall II Update December 2018

Now that the summer has passed it is a good time to assess the impact of the Tesla Powerwall II on the winter months when generation is very much lower.

I shall display two charts for comparison from my Solaredge monitoring software, One for October 2017 then the chart for October 2018. For the 2017 chart we did not have the Tesla fitted so it is a good comparison.

The key data is the Consumption of 655.33 kWh with 332.17 kWh generated by solar and export of 130.35 kWh against an import of 453.51 hours.

Contrast the above now with October 2018.

Key Aspects

Similar consumption 655 – 590

Better solar production in 2018 467 versus 332 last year

However there was a significant reduction in import from 453.51 compared to 143.57 this year. This is due to using the energy in the battery first and not exporting unused solar energy back to the grid (20 this year compared to 130 last year).

That is around 100 kWh I have not had to buy in from the grid compared to last year PLUS I am still getting paid the feed in tariff despite using it myself! The government cannot monitor what is fed back to the grid so the feed in tariff assumes 50% of what I generate goes back to the grid and pays a small amount for this electricity generation despite the fact I am not exporting it back to the grid but storing it in the Tesla battery for use later.

It is only very small numbers in the winter months I know but these little extra savings all mount up.

Add to this the savings I am making by switching to the green energy supplier BULB as can be seen from the chart below together with running the electric vehicle and the investment looks to be a sensible long term one.

 

Tesla Powerwall II