Is it safe to switch electric radiators on and off repeatedly?

Yes. Resistive heaters have no moving parts and are designed for hundreds of thousands of switching cycles. There is no mechanical wear, no startup surge worth worrying about, and no degradation from frequent on/off cycling. This is the same principle behind every thermostat that has ever existed.

Will my room get uncomfortably cold during the off hours?

It depends on the room's insulation and thermal mass. Most modern, reasonably insulated rooms retain heat for 1–3 hours after the heater turns off. Elewatt schedules heating during the cheapest hours — often late night and early morning — so the room stays warm through the day. You can also adjust how many hours per day the heater runs.

How much can I realistically save on heating?

Typically 20–40% of your heating electricity cost, depending on your contract type and usage. For a 1.5 kW radiator running 8 hours per day through a 180-day winter, that can be €30–€80 per season. The calculator on this page gives you a personalised estimate.

Which electric heaters are compatible with Elewatt?

Any plug-in electric heater up to 2.5 kW (12 A) works directly with a Shelly Plug S Gen3 — no wiring required. For hardwired heaters or panels up to 5.5 kW, a Shelly Plus 1PM (requires an electrician) is recommended. Oil-filled radiators, panel heaters, fan heaters, and infrared panels all work the same way.

Can I still control my heater manually?

Yes. The Shelly Smart Control app lets you turn the device on or off instantly, or set a manual override for a fixed duration. The physical button on the Shelly Plug also works. Elewatt pushes a fresh schedule each day, so the next day automation resumes automatically.

What if the electricity price is cheap all day?

Elewatt picks the cheapest N hours you specify (e.g. 8 h). If prices are uniformly low, it simply chooses the overall cheapest window. You always pay the lowest possible rate for the amount of heating time you need.

Education HubElectric Radiators Guide

Smart Heating · Cut Energy Costs

Electric Radiators & Smart Heating: Cut your winter electricity bill

In Baltic and Nordic countries, heating accounts for 40–60% of a household's winter electricity bill. Electric radiators are 100% efficient — meaning the biggest lever for savings isn't the device itself, but when it runs. Automating your radiators to heat during the cheapest hours can cut your heating bill by 30–40% without any change in comfort.

Get started free Connect Shelly

Radiator + Shelly Plug — Source: Google Gemini

Why smart heating makes sense

Electric radiators are the simplest heating system to automate: they're resistive loads that turn on and off instantly, with no warm-up cycles needed. A typical home needs 6–10 hours of heating per winter day — and with thermal mass in walls and furniture, heating for 4 hours during cheap overnight prices keeps the room warm for several hours more.

Share of winter electricity bill

40–60%

from heating in Baltic homes

Efficiency of electric radiators

100%

all electricity becomes heat

Potential savings

30–40%

on heating costs with smart scheduling

Choosing the right device

The right Shelly device depends on the radiator's rated power. Check the nameplate on your radiator.

Load	Current	Device	Notes
Single radiator ≤2.5 kW	≤12 A	Shelly Plug S Gen3	Plug & play
Radiator 2.5–5.5 kW	≤25 A	Shelly Plus 1PM	Requires wiring
Large / 3-phase systems	>25 A	Shelly Pro 3	⚠️ Professional install recommended

Mains wiring — safety note

Shelly Plus 1PM and Shelly Pro 3 involve mains (230 V / 400 V) wiring and should be installed by a licensed electrician. Experienced DIY enthusiasts can manage it with the detailed official documentation, but when in doubt, hire a professional. Always isolate the circuit before working on it.

How Elewatt automates your heating

1Install a Shelly device (Plug S Gen3 for ≤2.5 kW, Plus 1PM for larger) on your radiator circuit.
2In Elewatt, create a duration filter: e.g. "6 hours between 22:00–08:00".
3Link the filter to your Shelly device. Each evening, Elewatt picks the cheapest 6-hour window from tomorrow's prices and pushes the schedule.
4Your radiator heats the room during the cheapest night hours, and the thermal mass keeps it warm through the morning peak.

Create a filter About Shelly Plug S Gen3

Estimated savings by room size (winter)

Based on 180 winter days, average Nord Pool EE prices 2025–2026 (incl. Grid 3, taxes, 24% VAT): 14.5 c/kWh unoptimised vs 9.5 c/kWh with Elewatt.

Room	Power	Runtime	Annual kWh	Without Elewatt	With Elewatt	Savings
Small (12 m²)	1.0 kW	6 h/day	1 095 kWh	~€159	~€104	~€55/yr
Medium (20 m²)	1.5 kW	8 h/day	2 190 kWh	~€318	~€208	~€110/yr
Large (30 m²)	2.5 kW	8 h/day	3 650 kWh	~€529	~€347	~€182/yr

Calculate your savings

Adjust the sliders to match your radiator's power and daily runtime.

Savings Calculator

Estimate how much you could save by running your device during the cheapest hours.

Device power1.5 kW

0.1 kW22 kW

Hours per day8 h/day

1 h24 h

Days per year365 days

30 days365 days

Nord Pool EE + Elektrilevi grid + VAT · c/kWh (yearly avg)

0:00 · 14.1c

1:00 · 14.0c

2:00 · 13.1c

3:00 · 12.7c

4:00 · 12.6c

5:00 · 13.3c

6:00 · 16.2c

7:00 · 19.5c

8:00 · 21.8c

9:00 · 20.0c

10:00 · 17.8c

11:00 · 16.2c

12:00 · 15.6c

13:00 · 15.5c

14:00 · 15.5c

15:00 · 15.9c

16:00 · 16.7c

17:00 · 18.4c

18:00 · 20.9c

19:00 · 23.0c

20:00 · 23.7c

21:00 · 21.9c

22:00 · 18.7c

23:00 · 16.3c

Cheapest 8hMost expensive 8h

Daily usage

12.0 kWh/day

Annual usage

4380 kWh/year

With Elewatt

13.8 c/kWh avg

€607

per year

Without Elewatt

21.2 c/kWh avg

€928

per year

Your savings

Monthly

€27

Yearly

€322

Shelly Plug S Gen3 (€25) pays back in
0.9 months

Based on Nord Pool EE spot prices 01.03.2025–01.03.2026 + Elektrilevi VÕ grid fee + excise tax + 24% VAT. "Without Elewatt" assumes running during the most expensive hours. Actual savings vary by country, grid, and season.

Ready to cut your heating bill?

Create a free Elewatt account, connect your Shelly device and let automation handle the rest — warm rooms, lower bills.

Create free account About Shelly Plug S Gen3

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