Solar PV and Tesla Powerwall 2 stats for December 2020

This is my December 2020 solar pv and Tesla 
Powerwall 2 performance here in the UK   along with our Tesla Model 3 and Kona 
electric costs and usage. So stay tuned.   Hi John here and welcome. In this video I'm 
going to take you through our solar pv and   Tesla Powerwall 2 performance for the month of 
December 2020. Plus stats and usage information   for our Tesla Model 3 and the Hyundai Kona 
electric and myenergi eddi and zappi. I will be   publishing in the next few days a full 2020 review 
of our solar power wall and battery electric cars   all of that performance. Therefore, I'm 
going to keep this video fairly brief.   In the description down below is a list 
of all our components for our system   so please have a look down there if 
you're not familiar with our setup.   Let's get straight into it. So in December we 
produced a total of 100… excuse me laughing…   a total of 186kWh from our 2 separate pv arrays. 
We had an average daily solar generation of just   6kWh for the month. December wasn't a great month 
for solar very very grey.

And you'll certainly   see that when we look at the day-to-day chart 
so stay tuned because that's a bit of a doozy. If we look at the solar pv totals for 
both arrays our 4kW array produced 116kWh   and our newer 2.34 kW array produced 70kWh. 
Comparing that to December last year with   the identical setup you can see we managed 
much more solar generation. Another 61kWh   over the course of the month.

2020 not great for 
us. So let me know in the comment section down   below how you got on with your solar generation 
if you have solar. I love to hear what your totals   were and your system size and other viewers like 
to read your comments and see how everyone got on.   Thank you in advance to those of you who do 
comment and it is really appreciated because it   creates data sharing and a sense of community as 

So thank you. Let's look at the Powerwall 2   and solar contribution to our overall self-power. 
Our Powerwall is in Cost Saving mode we are with   Octopus Energy on their Agile tariff. And Cost 
Saving mode the battery provides the power to   the house for the peak period between 4pm and 
7pm every day that's its underlying principle.   During December we were 34% self-powered from the 
Powerwall and the contributions were 26% and 8%   as you can see from the stack chart. The 
8% came from solar generation and the 26%   came from the Powerwall. So the Powerwall 
was doing all the work basically. More   than 3 times the work in fact and it's hardly 
surprising the Powerwall picked up the slack   due to such a low solar production for the month. Let's have a look at the peak 
and off-peak for our self-power.   The Powerwall did a really good job supplying our 
home's power needs during the peak period between   4pm and 7pm. Within the Tesla Powerwall app 
I've extended the peak period time slot out   to 8pm as electricity unit pricing can sometimes 
be a little high at that time of night.

In effect   the peak self-power figure here is for 
four hours from 4pm through to 8pm.   The percentages on this chart represents 
the performance of the Powerwall's ability   to supply the house rather than pulling from the 
grid to meet the house's needs. The months along   the bottom are only populated with data when 
we are in Cost Saving mode with the Powerwall.   The red columns represent the 4hr peak time 
and looking at December 2020 column for 99%   of the time in that 4hr peak period we were on 
battery power with no pull from the grid. Well   just 1% was grid energy during that peak time. I 
don't actually have the exact figures yet as my   electricity bill hasn't arrived in time for making 
this video. However, extracting the data from the   Octopuswatchdog app it shows 2.88kWh of usage for 
a cost of 0.74 pence for that one percent of grid   pull during the peak rates over the course 
of the month.

So small change then really.   The green column represents the 
remaining 20 hours of the day   during that time we were on battery and solar for 
just 5% of the time. Grey, dull, short daylight   winter days are the worst for solar generation. 
Still at least the shortest day has been and   gone and now we are starting to edge towards more 
daylight each day. Around 2 minutes extra per day. Let's have a look at the pv year on year chart.   Here's the month of December solar 
generation going back to 2011.   The totals for years 2011 to 2018 will be for the 
original 4kW system.

The 2019 and 2020 figures   are for both arrays. If you recall the original 
4kW array produced 116kWh in December 2020   making it the second worst December. December 
2015 pipping it to the worst month by just 5kWh.   The new array managed 70kWh giving us 
the 186kWh total that you see there. Powerwall in and out, very brief look at that.   The Powerwall had an 89% round trip efficiency 
for the month for what we managed to store versus   what the power was able to supply. We 
stored 347kWh and it supplied back 310kWh. Let's skip along merrily to the day by day. 
This chart gives you what happened on a sort   of day by day usage. The legend is, blue 
is house usage, yellow is solar generation,   orange is export to the grid 
and red is import from the grid. Where is the yellow I hear you ask? Have you 
forgotten to add that data John? No, it is there.   There were just 5 days during the month where we 
saw solar production above 15kWh in a single day.   For the first time ever we had one day with 
zero generation.

That was on the 23rd December.   Previously our lowest recorded generation was 
on December 26th & 27th of 2019 at 400watts   on each day. I never thought I would see zero 
solar generation in a day but there you go. So   how did everyone else get on towards the end of 
December? Was your December 23rd as bad as ours?   Comment down below with your worst 
day of solar generation this year.   Let's have a look at December 2020 overall totals. 
This chart shows the overall totals for the 4 data   sources we've just looked at in the day by day. 
I guess the house usage is the key one here at   1.265kWh of usage over the course of the month. 
And most of that would have been coming from the   grid due to the poor solar production for the 
month. Let's skip forward because I'm about to   cover the grid usage in a little more detail so 
I won't dwell on it on this particular chart. This chart shows our average daily house usage 
and our average daily grid uses over the month.   Our average daily house usage was 
up against November's at 40.kWh   from 31.6kWh and that's the blue line.

average each day we pulled 36.5kWh from the grid.   Again up on November's figures of 22.8kWh and 
that's the red line. This is what we sent to the   grid. We sent 24.6kWh of excess solar generated 
back to the grid in December. This was towards   the beginning of the month on the 5th and 6th of 
December and we were actually out all day and I   forgot to plug in one of the cars before we left 
home and both days were surprisingly sunny, hey   ho! So this tracks what we pulled from the grid 
each month. A total of 1,131kWh from the grid and   I guess there were 2 reasons for this increase in 
grid usage this month.

1) is less solar production   and 2) there were a few days of negative, or 
plunge, pricing which we took advantage of   to charge up one of the cars, and the Powerwall, 
run the dishwasher, washing machines and so on.   There was also some very low electricity rates 
on some very windy days so we benefited there   too. So whilst the grid usage does actually 
look high, the electricity bill will not   reflect that as there are some credits in 
there as well and some very very low rates. If we look across to December 2019 you can see 
that we use less in 2020 than we did in 2019.   1,131kWh versus 1,299kWh.

a small token takeaway there.   I'm now hoping that we're heading towards lower 
grid usage as the months progress. Looking at   the historical charts that seems likely. However, 
you can never tell with the great British weather.   Another Beast from the East like we had in 2018 
we'll certainly knock all that on the head. Let's have a look at the eddi. This chart is for 
the eddi which heats our hot water by diverting   excess solar energy once the Tesla Powerwall 
battery is full. Lack of sunshine clearly had   an impact here with just 6kWh of electricity 
diverted from excess solar. Let's move on to   the zappi. This is the zappi for December 2020, 
it covers the Tesla Model 3 and the Hyundai Kona.   The Tesla Model 3 is covered 178 miles during the 
month bringing its total mileage to 8,170 miles.   We did 1 Supercharging session at Wyboston 
Lakes, which the first time we've been there   it's fairly near to us as well. So that was 
nice. We were 'Billy no mates' there by the way   and it was free because we have referral miles. 
So thank you to those people that have used our   referral code when purchasing their Tesla 
and gained a 1,000 free supercharging miles   each.

We were also, while we were charging, in 
Santa mode which you can see there on the screen.   The remainder, or should i say the reindeer, of 
the charges was all done at home on the zappi.   We added 155.79kWh of which just amazingly 1% 
was from excess solar energy. That 1% works   out at 4.86kWh. They other 99% was from the 
grid and again all at cheap off-peak rates   as I mentioned earlier. We also had some plunge 
pricing and negative pricing during December which   we took advantage of to top up the Tesla. In terms 
of working out the costs here I've used an average   of 6p per kilowatt to calculate the costs as I've 
again not had the Octopus Agile December bill   through yet. The 178 miles covered in the Tesla 
during the month cost us £0.05 pounds per mile.   The Kona covered 220 miles in the month and now 
has a total mileage of 10,702 miles.

We did one   public charging in the Kona at Rushden Lakes Pod 
Point, which was on free vend and added 13kWh.   We were there all day the remaining 100.64kWh 
was added at home by the zappi. The 220   miles covered in the Kona during the month cost us 
£0.03 pounds per mile. So finally please comment,   like and share. Any of those actions really 
help to get the video shown to more people   which in turn obviously helps my channel grow.   Thank you for watching and I will see you 
on the next video. Alright take care. Bye..

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