Throughout 2025, I spoke a few times about our home energy solution, including our grid usage, our solar array and our Tesla Powerwall batteries. Now that I have a full year of data, I wanted to take a look at exactly how everything is working out, and, in alignment with our objectives, how much money we've saved!
Our setup
Just to give a quick overview of what we're working with, here are the details on our solar, battery and tariff situation:
☀️Solar Panels: We have 14x Perlight solar panels managed by Enphase that make up the 4.2kWp array on our roof, and they produce energy when the sun shines, which isn't as often as I'd like in the UK!
🔋Tesla Powerwalls: We have 3x Tesla Powerwall 2 in our garage that were purchased to help us load-shift our energy usage. Electricity is very expensive in the UK and moving from peak usage which is 05:30 to 23:30 at ~£0.28/kWh, to off-peak usage, which is 23:30 - 05:30 at ~£0.07/kWh, is a significant cost saving.
💡Smart Tariff: My wife and I both drive electric cars and our electricity provider, Octopus Energy, has a Smart Charging tariff. If we plug in one of our cars, and cheap electricity is available, they will activate the charger and allow us to use the off-peak rate, even at peak times.
Now that we have some basic info, let's get into the details!
Grid Import
I have 3 sources of data for our grid import, and all of them align pretty well in terms of their measurements. I have the amount our electricity supplier charged us for, I have my own CT Clamp going via a Shelly EM that feeds in to Home Assistant, and I have the Tesla Gateway which controls all grid import into our home.
Starting with my Home Assistant data, these are the relevant readings.
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