Smart EV Charging: Save money by charging at the right time
Electric vehicles consume 15–30 kWh per 100 km. At peak electricity prices, that can cost twice as much as charging during off-peak hours. Day-ahead spot prices can swing several-fold within a single day, which makes smart scheduling one of the highest-impact changes you can make.
Why does charging time matter?
Day-ahead spot prices change every hour — every 15 minutes in many markets. The most expensive hour of the day often costs several times the cheapest, and the gap is widest in winter. An EV consuming 7.4 kW for 2 hours a day costs roughly:
At peak hours
…
per charge session
At off-peak hours
…
per charge session
Annual difference
…
for a typical EV
Most EV chargers don't know what electricity costs right now. They just charge whenever you plug in. Elewatt changes that by pushing a daily on/off schedule to your smart relay so charging always happens during the cheapest window.
Choosing the right device
The right smart relay depends on your charger's power. Use the table below to find the correct device for your setup.
| Use case | Max current | Device | Notes |
|---|---|---|---|
| Overnight trickle (≤2.5 kW) | 12 A | Shelly Plug S Gen3 | Plug & play, no installation |
| Standard charger (≤7.4 kW) | 32 A single-phase | Shelly Plus 1PM | Requires wiring |
| 3-phase 11 kW charger | 3×16 A | TopAC EVE01-11R | Native Shelly device with REST API |
| Heavy 3-phase (up to ~33 kW) | 3×32 A / 3×48 A | Shelly Pro 3 | Professional install required |
- Max current
- 12 A
- Device
- Shelly Plug S Gen3
- Notes
- Plug & play, no installation
- Max current
- 32 A single-phase
- Device
- Shelly Plus 1PM
- Notes
- Requires wiring
- Max current
- 3×16 A
- Device
- TopAC EVE01-11R
- Notes
- Native Shelly device with REST API
- Max current
- 3×32 A / 3×48 A
- Device
- Shelly Pro 3
- Notes
- Professional install required
TopAC EVE01-11R — 3-phase 11 kW EV charger
The TopAC EVE01-11R is a Shelly ecosystem partner product available via shelly.com. It's a 3-phase 11 kW wall box with native REST API, MQTT, and Shelly Cloud support — meaning it's controlled in Elewatt exactly like any other Shelly device, using the same filter and schedule system.
This makes it the cleanest solution for 3-phase setups: no additional relay needed, and scheduling works out of the box.
How Elewatt automates your EV charging
- 1Connect your Shelly device in Elewatt (via Shelly Cloud).
- 2Create a duration filter: e.g. "4 hours between 23:00–07:00".
- 3Link the filter to your EV charger. Elewatt finds the cheapest 4-hour window and pushes the schedule to the device every evening.
- 4Plug in your car before bed. It charges automatically during the cheapest hours, every day.
Calculate your savings
Adjust the sliders to match your EV's onboard charger power and typical daily charging time.
Savings Calculator
Estimate how much you could save by running your device during the cheapest hours.
Spot price + grid fees + taxes, Estonia · c/kWh (12-month avg)
Daily usage
14.8 kWh/day
Annual usage
5402 kWh/year
Without Elewatt
28.2 c/kWh avg
1525 €
per year
With Elewatt
12.5 c/kWh avg
677 €
per year
Your savings
Monthly
71 €
Yearly
847 €
Shelly Plus 1PM (35 €) pays back in
0.5 months
Estonia: spot prices over the last 12 months + grid fees (Elektrilevi) + taxes and VAT. "Without Elewatt" assumes running during the most expensive hours. Actual savings vary by grid package and season.
Ready to charge smarter?
Create a free Elewatt account, connect your Shelly device and set up your first charging schedule in minutes.