u/Stumptown_Mike

I've been using a Shelly Plug US Gen4 on my Level 1 EV charger at home and wanted to share how I'm pulling the session data via the Shelly Cloud API to calculate actual cost per mile.

The basic flow: the Shelly captures kWh delivered and timestamps for each charging session. My app pulls that data, applies my utility's time-of-use rate schedule, and calculates exact cost per session — not an estimate based on national averages, but what I actually paid my utility for that specific session at that specific time of day.

The screenshot shows my recent sessions from the dashboard. You can see the per-session cost and kWh varying based on when I charged and which TOU tier applied (sometimes it's in-between because it blends sessions crossing TOU).

A few things I found interesting building this:

• The Shelly data is clean and consistent — session start/end times and energy readings come through reliably
• TOU calculations make a meaningful difference. The same kWh costs noticeably more if you charge during peak vs overnight
• Level 1 on a standard 120V outlet works well for this — well within the Shelly's rated capacity charging overnight at 12A (my vehicle is limited to 8A due to being on a shared circuit)

Curious if anyone else is doing something similar with the Shelly API for energy cost tracking on their EV.

EV Charging Sessions Across TOU

I charge my Bolt EV overnight on a standard 120V outlet and I'm wondering if the Shelly Plug US Gen4 can handle the load. Level 1 EV charging draws around 12A continuously for several hours — well within the rated capacity on paper, but curious if anyone has real-world experience with this specific use case.

The reason I'm asking: I built a small web app that pulls session data from the Shelly API to calculate my actual cost per mile using my utility's TOU rate schedule. Before I recommend it to other EV owners I want to make sure the hardware holds up long-term.

Anyone running a Shelly Plug on an EV charger?

My father-in-law is paying California gas prices and asked what my Bolt costs per mile. I had no good answer — not for him, not even for myself. The data is somewhere across my utility account and odometer readings but there's no easy way to pull it together.

I ended up plugging a Shelly smart plug (~$25) into my 120V outlet to measure exactly what goes into the car each Level 1 session, then built a little web app to calculate cost per session and cost per mile using my actual TOU rate. My number came out to $0.056/mile, which is the answer I should have had ready months ago.

Curious if others have solved this differently. The Shelly only works on 120V outlets so Level 2 folks would have to log sessions manually, but the math works either way.