Four years of invoices and inverter data from a 6.4 kWp zero-export rooftop PV system with a BYD battery: what each part cost, what it saved, and which one was a bad buy.
Rooftop PV, four winters later
The night my Model 3 died in its sleep: “High Voltage Fuse A Blown” (P0A9501)
Tesla Model 3 dead overnight with a false “High Voltage Fuse A Blown” alert – reconstructed to the second with Home Assistant, TeslaMate and BLE.
The clear-sky line
Three years of Fronius GEN24 data distilled into a clear-sky ideal-produce curve as a Home Assistant sensor – the fit, the validation, the surprises.
€14.5k into DIY solar in 2022, or the same into VUAA?
€14.5k into DIY solar in 2022, or the same into VUAA? ETF would be up ~€12.5k on paper, ~€7k after inflation. But the panels generated 27.7 MWh so far – that’s ~€3.5k of grid power I never bought. real gap: ~€4k and shrinking every year electricity gets pricier. no regrets
Our Tesla M3 efficiency vs. outside temperature stats for t…
Our Tesla M3 efficiency vs. outside temperature stats for the last 10K km driven, collected using TeslaMate. No surprises here, driving at 20 °C outside is most efficient
EV electricity since late Feb
Have not paid for EV electricity since late Feb, going purely on solar. More than 800km driven so far, feels illegal.
60 km EV commute’s spent energy recovered by free solar
Today's 60 km EV commute's spent energy is fully recovered by free solar charging once back home. And it's still only February. Impressive.
5000 km driven with our new Tesla
Slightly over 5000 km driven with our new Tesla in the three months since we got it. The app estimates 625 BGN (320 EUR) in savings compared to an ICE vehicle. Actual savings are even higher, as 16% of the charged power is free PV produced at home.
TeslaMate indoor and underground garage position tracking
I've been running TeslaMate for about a month and am quite impressed by the detailed metrics it collects, especially the precise indoor and underground garage position tracking. I assume it's based on vehicle speed and wheel direction.
Too cold outside, Tesla won’t start
Too cold outside, Tesla won’t start. Any tips?
7.4MWh solar power production at home in 2025
7.4MWh solar power production at home in 2025, not bad
Tesla’s charging port logo’s green LED
Our Tesla’s charging port logo’s green LED in the RGB died, so the logo is now purplish instead of white when idle and reddish instead of green when charging. Scheduled a free service replacement, but overall not cool.
Can’t get enough of that free EV charging
Can't get enough of that "free" EV charging 😉
Fronius smart meter died at 4am today
Fronius smart meter died at 4am today, leaving the solar system inoperable. No obvious signs of damage. Luckily I had a spare and replaced it, but wondering what happened..
PV storage using Dala’s battery emulator
Adding this to my “want, but never will have” list, to be used as PV storage using Dala’s battery emulator https://vivnevs.com/products/62kwh-nissan-leaf-battery-pack-180ah-catl-lithium-battery-for-leaf-battery-upgrade
Home-assistant automation to pause solar battery charging
Created a Home-assistant automation to pause the solar battery charging at ~80% and only charge it to 100% at the last possible moment. This is to minimize time spent at full charge, which apparently is bad for the battery. It considers the estimated remaining PV production.
Rooting Tesla cars and tampering with mileage
So I understand rooting Tesla cars is now a thing, and tampering with mileage is possible and done on the second hand market 🙁 . Enabling free supercharging possible too. Explanation and details here, in Bulgarian: https://youtu.be/2Hxg5jsR2Ns?si=bS9ywSc_Xw3Jqu6C
BYD 7.68kWh LiFePO4 solar battery
Data collected over nearly two years shows our BYD 7.68kWh LiFePO4 solar battery operates at an average of 94% efficiency (charged vs discharged). Capacity degradation is at 2%
DEV.BG tech talk: Intelligent Synergy: Heat Pump, PV & Home Assistant
My DEV.BG tech talk on making the heat pump, the PV system and Home Assistant work together – slides and video, in Bulgarian.
6.4kWp @Fronius PV system produced 7.05 MWh
In 2023, our 6.4kWp @Fronius PV system produced 7.05 MWh, fulfilling 60% of our electrical needs and saving us ~920 EUR. Our 7.68kWh BYD battery stored 1.83 MWh for later use and the OhmPilot diverter captured an extra 1.84 MWh, boosting our self-consumption by about 26%. #solar
World’s slowest EV
My son just showed up at my office with this “thing”, supposedly world’s slowest EV. Thankfully, he didn’t buy it and just borrowed it for the day
Our own solar panels provided for 91% of our energy needs
Relying less on the grid this month, as our own solar panels provided for 91% of our energy needs.
Tomorrow’s PV production estimate for our system
Tomorrow’s PV production estimate for our system is near 44kWh. We’ve sized it to support future EV charging. Currently, we can’t self-consume that much, and grid feed-in is complicated by local bureaucratic obstacles. Hate to see it go to waste.
Old Nissan Leaf batteries to a Fronius GEN24 inverter
Thought I was done with solar system spending, but then someone develops a way to connect old Nissan Leaf batteries to a Fronius GEN24 inverter. Now remains to make a compelling case for this new budget dent to my better half. https://github.com/dalathegreat/BYD-Battery-Emulator-For-Gen24 Repeating in my head: "want != need"
1 MWh solar production milestone for 2023
Passed the 1 MWh solar production milestone for 2023 today. Not bad. My setup is described in this blog post: https://harizanov.com/2023/01/rooftop-pv-installation/
LiFePo4 (LFP) chemistry
Interesting paper on "Degradation of Commercial Lithium-Ion Cells as a Function of Chemistry and Cycling Conditions" here: https://iopscience.iop.org/article/10.1149/1945-7111/abae37/pdf; Three degradation factors are explored: 1) Temperature, 2) DoD and 3) Discharge rate. (1/2) I specifically care about LiFePo4 (LFP) chemistry, because our solar system's BYD battery is such. Strange to see that a 100% DoD doesn't…
BYD HVS 7.7kWh BMU update
Our solar system’s battery app (BYD HVS 7.7kWh) says its BMU needs an update. No release notes or details on what’s being fixed. Feeling brave and proceeding with the update anyway, WCGW
Rooftop PV installation
New blog post: Rooftop PV installation https://harizanov.com/2023/01/rooftop-pv-installation/ #solar #DIY
Rooftop PV installation
Why rooftop solar is a hard sell in Bulgaria and how I did it anyway – the full story of my PV installation, from permits to first kWh.
55kWh Tesla Model 3 battery with Fronius GEN24 solar
Dala's EV Repair managed to configure and use a 55kWh Tesla Model 3 battery with @froniussolar GEN24 #solar inverter. That opens new options for EV battery repurposing after their useful life. https://www.youtube.com/watch?v=-s7lODLDOiQ&ab_channel=Dala%27sEVRepair
Solar production at winter solstice exceeds my expectations
#Solar production at winter solstice exceeds my expectations, a whopping 19.5kWh given it was hazy 10-11am. This is out of a 6.4kWp PV installation in Sofia, Bulgaria.
Solar production dropped to zero
This guy showed up, and solar production dropped to zero last couple days. My panels aren’t easily accessible (rooftop) so that I could remove the snow. Enjoying the winter anyway, forecast is that snow will melt in a day or two.