Back in July I posted about changing the application that sits on my server to collect data from around the house and send it to Splunk. That app has been sending data for over 8 months now and during the winter we noticed that the Powerwall was consuming data from the grid nearly every night, yet not charging the battery above the reserved 5% mark.
I contacted Tesla to find out what was happening as these events were quite frequent in the winder months. Their response was that they were “low state of energy” or also known as “emergency grid charging events”. In the below graphs each of the orange spikes below the zero line and with a corresponding spike in the blue line at the same time period represents one of these low state of energy events.
Tesla offered some options on how to reduce the number of these low state of energy events but for the time being we’ve decided to leave the settings as is because the summer months are on the way and the number of low state of energy events has already started to reduce.
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:
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
I’ve had my solar panels since October 2011 (details about my system can be found on this post) and I’m always telling people how good they are. When I tell people about my solar panels, I get one question – “how much do they generate” and the second is a statement that always makes me want to bang my head against a brick wall – “… but solar panels don’t work in the winter!” Don’t they??
When I first started telling people they should buy solar panels, all I could them was how much electricity they would generate and potentially cut from their bill, but since then I’ve added monitoring to the system which uploads the data to the internet. After the person I’m talking to has used the infamous statement about not producing electricity in the winter, I then proceed to show them the stats from my solar panels.
In the UK, winter solstice is a day between 20th and 23rd December and for more than a week each side of winter solstice, there are less than 8 hours of sunshine in a day. It’s quite literally the worst generation time of the year for solar panels in the UK – especially combined with the weather that you can get at that time of year… But when the sun does shine in the winter, you can get very good solar output days!
This December gone, I checked my system from work during lunch (as I do most days! sad, yes I know…) and noticed the solar panels had heated the hot water. To heat the hot water, there has to be enough energy generated by the solar panels to not only cover the house’ standby usage (350 ish W/h), any additional power being used by family members and also the 1kW/h immersion.
What’s more impressive is that the date was 16th December!
(the red block indicates the immersion is switched on)
In fact we even had brief solar water heating on the 19th and 20th but they aren’t as visually impressive…
But what all three of those charts show is that solar panels do work in the winter. They can even generate enough electricity to cause a surplus and power devices around the home!
It is true that the panels do not generate as much electricity during the winter, due to the angle of the sun in the sky and the length of the day, but we still generate in the order of 100kW/h of electricity each December.
And on a perfect day, it’s possible to generate 9kW/h.