Monitor a rental's electricity in real time — and heat it for less
Whether you let a flat long-term, host short stays or rent out a cottage, you usually find out what it used when the bill arrives. A Shelly energy meter and Elewatt show consumption and cost as it happens, and heat the place in the cheapest hours while it stands empty.
A sub-meter you can read from anywhere
A classic sub-meter shows a number on a display in the flat. A Shelly energy meter in the flat's board sends the same measurement to Shelly Cloud, and Elewatt prices it with the day's spot price and your grid fees. You see today's kWh and euros for each property without going there.
For a 3-phase flat or house, use a Shelly Pro 3EM-3CT63 (about €131); for a single-phase flat or cottage, a Pro EM-50 (about €102). Both mount on the DIN rail, so they need an electrician.
Monitoring vs. billing: where the law draws the line
Shelly meters are not MID-certified. That is fine for watching consumption and for flat-rate or included-in-rent arrangements. Billing tenants per kWh is a different matter:
| Country | Billing tenants per kWh |
|---|---|
| Germany | Only with a verified (geeicht) meter. Billing from an unverified sub-meter breaks § 37 MessEG; fines go up to €50,000. |
| Finland | Needs a MID-approved meter. A flat fee, or electricity included in the rent, needs no meter at all. |
| Sweden | A tenancy-law matter. A charge sold as individually metered (IMD) must follow the measured use. |
| Estonia | Electricity is an ancillary cost; the billing method has to be agreed in the lease and can't be changed without the tenant's consent. |
- Billing tenants per kWh
- Only with a verified (geeicht) meter. Billing from an unverified sub-meter breaks § 37 MessEG; fines go up to €50,000.
- Billing tenants per kWh
- Needs a MID-approved meter. A flat fee, or electricity included in the rent, needs no meter at all.
- Billing tenants per kWh
- A tenancy-law matter. A charge sold as individually metered (IMD) must follow the measured use.
- Billing tenants per kWh
- Electricity is an ancillary cost; the billing method has to be agreed in the lease and can't be changed without the tenant's consent.
A summary, not legal advice. Check your own country's rules and your lease before charging by the kWh.
Short-term rentals: catch the heater left on full
Short-stay hosts know the pattern: radiators at maximum with a window open, the sauna left on, a car charged from a garden socket. Real-time consumption shows it the same day, not a month later. Between stays, heating and hot water can run only in the cheapest hours, and you switch back to comfort before the next guest arrives.
Cottages and holiday homes: keep them warm for less
An empty cottage in winter only needs enough heat to stay dry and above freezing, and that heat can come in the cheapest hours. Put the radiators or floor heating on metered Shelly relays, give them a price filter, and turn them up from your phone the day before you — or your guests — arrive. Heat pumps in holiday homes work the same way if they are Daikin or Samsung units.
Keep the frost guard separate. A circuit whose only job is to stop pipes freezing should not be on a relay that a price filter can switch off.
Electric Radiators on Spot Prices: Heat in the Cheap Hours →Daikin Onecta →
Several properties, one view
Each property can have its own electricity contract, grid operator and price area in Elewatt, so every place is priced correctly. The Business plan covers 5 contracts and 20 devices and can be extended.
Who gains? If the tenant has their own electricity contract, the savings from cheap-hour heating are theirs. Automation pays the landlord directly when electricity is in the landlord's name — common areas, included-in-rent lets, short stays and empty periods.
Setting up a rental
Four steps per property.
- 1
Fit a meter
An electrician installs a Shelly Pro 3EM-3CT63 or Pro EM-50 in the property's board and adds metered relays for the heating and water heater.
- 2
Connect to Elewatt
Link your Shelly Cloud account and add the property's electricity contract and grid operator, so costs are priced correctly.
- 3
Set price filters
Give the heating and water heater a filter — for example the 8 cheapest hours for background heat in an empty cottage.
- 4
Check in from anywhere
Follow consumption and cost per property and switch heating to comfort mode before arrival.
Estimate the savings for a rental cottage
The calculator starts with an electrically heated cottage: radiators, a water heater and floor heating. Adjust it to your property.
Savings Calculator
Estimate how much you could save by running your device during the cheapest hours.
List only devices that can wait for cheaper hours. Click a row to see its hours on the chart.
Spot price + grid fees + taxes, Estonia · c/kWh (12-month avg)
Daily usage
50.0 kWh/day
Annual usage
18250 kWh/year
Without Elewatt
26.3 c/kWh avg
4793 €
per year
With Elewatt
13.6 c/kWh avg
2477 €
per year
Your savings
Monthly
193 €
Yearly
2316 €
Shelly hardware (94 €) 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.
The Shelly Pro lineup: switchboard hardware without the BMS price
Shelly's Pro devices mount on a DIN rail in the distribution board, connect over Ethernet as well as Wi-Fi, and run the same scripting and schedules as the rest of the Shelly range. An electrician fits them like any other switchboard module, and Elewatt drives them through Shelly Cloud. Shelly sells the Pro line with a 5-year warranty.
| Device | What it does | Use it for | Price |
|---|---|---|---|
| Shelly Pro 3 | 3 relays, 16 A each (48 A total). Switches three separate circuits or one 3-phase load. No power metering. | 3-phase sauna heaters, large water heaters, contactor coils for bigger loads | 90 € |
| Shelly Pro 3EM-3CT63 | 3-phase energy meter, 0–63 A. The CT clamps straight over a breaker. Keeps 60 days of 1-minute data. | Real-time consumption and cost of a sub-board, a 3-phase circuit or a whole flat | 131 € |
| Shelly Pro 4PM | 4 relays, 16 A each (40 A total), with per-channel metering and a small screen. | Radiators by zone, several water heaters, one device per stairwell or room group | 118 € |
| Shelly Pro 2PM | 2 metered relays, 16 A each (25 A total). | Two single-phase loads where you want savings per device | 100 € |
| Shelly Pro 1PM | 1 metered relay, 16 A. | A single water heater or radiator circuit with its own savings figure | 76 € |
| Shelly Pro EM-50 | Single-phase meter with two 50 A clamps, plus a 2 A relay to drive a contactor. | Metering a single-phase flat or cottage; switching a load through a contactor | 102 € |
| Shelly Pro 3EM-400 | 3-phase meter, 0–400 A. | The main incomer of a larger building | 274 € |
- What it does
- 3 relays, 16 A each (48 A total). Switches three separate circuits or one 3-phase load. No power metering.
- Use it for
- 3-phase sauna heaters, large water heaters, contactor coils for bigger loads
- Price
- 90 €
- What it does
- 3-phase energy meter, 0–63 A. The CT clamps straight over a breaker. Keeps 60 days of 1-minute data.
- Use it for
- Real-time consumption and cost of a sub-board, a 3-phase circuit or a whole flat
- Price
- 131 €
- What it does
- 4 relays, 16 A each (40 A total), with per-channel metering and a small screen.
- Use it for
- Radiators by zone, several water heaters, one device per stairwell or room group
- Price
- 118 €
- What it does
- 2 metered relays, 16 A each (25 A total).
- Use it for
- Two single-phase loads where you want savings per device
- Price
- 100 €
- What it does
- 1 metered relay, 16 A.
- Use it for
- A single water heater or radiator circuit with its own savings figure
- Price
- 76 €
- What it does
- Single-phase meter with two 50 A clamps, plus a 2 A relay to drive a contactor.
- Use it for
- Metering a single-phase flat or cottage; switching a load through a contactor
- Price
- 102 €
- What it does
- 3-phase meter, 0–400 A.
- Use it for
- The main incomer of a larger building
- Price
- 274 €
Prices from the shelly.com EU shop including VAT, checked on 29 September 2026. They vary by country and retailer.
Over 16 A? Use a contactor
A Shelly relay is rated 16 A per channel. Heavier loads, and anything with a motor or compressor, should be switched by a contactor that the Shelly controls — standard switchboard work for an electrician, and the way Shelly itself recommends load shedding.
Monitoring, not billing
Shelly meters are accurate to about 1% but they are not MID-certified — Shelly says its devices are not designed for MID. Use them to see and allocate consumption. Where the law requires a certified meter to bill per kWh, keep the certified meter for billing.
Shelly's statement on MID →Shelly's own guides for buildings
Shelly publishes its own material for property managers and installers:
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