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 well. 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. On 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. So 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.