What is the cheapest way to automate my water heater with spot prices?

Open-source Shelly scripts are free and work well if you are technically comfortable — but the best-known ones (shelly-porssisahko, Spot-hinta.fi) only cover Nordic and Baltic price zones out of the box. For most households, a dedicated app like Elewatt is faster to set up and adds savings tracking and filter rules without any coding.

Do I need to switch my electricity supplier to use spot prices?

Not necessarily. Elewatt isn't an electricity supplier — it works with whichever supplier you have. What you do need for real savings is a contract billed at the spot price hour by hour (or per quarter-hour), often called a spot, dynamic or exchange-price contract. Many suppliers offer one, so changing the contract is often enough; if yours doesn't, you'd need to switch. Then connect your device and start scheduling.

What is the difference between Tibber and Elewatt?

Tibber is a full electricity supplier — you must switch your electricity contract to them to use their smart scheduling features. It operates in Sweden, Norway, Germany and the Netherlands. Elewatt works with your existing contract and supplier.

Which countries does Elewatt support?

Elewatt supports the day-ahead price zones of most European countries, including multi-zone markets such as Sweden, Norway, Denmark and Italy. Day-ahead prices are fetched automatically every afternoon as soon as they are published, and device schedules are updated for the next 24 hours.

Is Home Assistant worth setting up just for water heater scheduling?

If you already use Home Assistant for other things, a spot-price integration (Nord Pool or ENTSO-E) combined with Shelly is excellent and highly configurable. If you only want to schedule a single water heater, the setup cost — dedicated hardware, time to configure, ongoing maintenance — is significant compared to a no-code app that takes minutes to get running.

How much can I realistically save per year with automated scheduling?

It depends on your contract, the size of your water heater, your usage and how much prices in your market swing from hour to hour. The savings come from shifting 2–4 hours of runtime per day from expensive peak hours to the cheapest hours — typically late at night or around midday when solar output is high. Elewatt tracks actual savings month by month so you see the real number for your home.

Ecosystem Guide

Smart Home Spot Price Apps: A Guide to the Ecosystem

A look at the tools helping households shift electricity use to cheaper, greener hours — open-source scripts, platforms, and apps, each built for different needs and regions.

Reedik Lindau

Published 8 March 2026 · Updated 6 October 2026

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The Automation Gap

Spot-linked, dynamic electricity prices are now an option for households across Europe. On a typical day the price can swing several-fold between the cheapest and the most expensive hour — so a water heater that runs at 7 AM instead of 3 AM can cost two to three times as much. Most people know this. Most people still don't automate around it.

The tools to solve this exist. A growing ecosystem of apps, scripts, and platforms lets households shift water heater, heat pump, and EV charging loads to the cheapest hours automatically. The options look very different from each other — scripts for developers, platforms for DIY enthusiasts, and apps for households who just want it to work.

Typical daily price spread

2–5×

cheapest vs. most expensive hour on a typical day

Daily runtime needed

2–4 hrs

minimum for a standard 200 L water heater

Annual savings potential

15 min

day-ahead price resolution in the EU since October 2025

Elewatt price filter dashboard — scheduling devices to run during cheapest electricity hours

Three Ways to Solve It

The solutions fall into three broad categories, each with a different target user, setup complexity, and feature set.

Open-source scripts

Scripts that run directly on the Shelly device itself, fetching day-ahead prices and switching the relay without any external server or account. No subscription, no app, no data leaves your network.

✓ Free, private, works indefinitely

✗ Requires developer knowledge to install and configure

Home automation platforms

Home Assistant with a spot-price integration (ENTSO-E) gives advanced users complete control — price-based automations for every device in the house. Very powerful once running, but needs a dedicated Raspberry Pi or server.

✓ Highly flexible, large community

✗ High setup barrier, hardware required

Dedicated apps

Cloud-based apps that handle the scheduling logic, UI, and device communication for you. Create an account, connect a device, set your rules. No scripts, no hardware.

✓ No-code, savings tracking, managed updates

✗ Subscription cost, device ecosystem may be limited

Tools Available in 2026

Here is an overview of the main tools helping households make smarter use of spot price electricity as of 2026. Each takes a different approach — the right fit depends on your region, devices, and technical comfort.

Solution	Type	Device control	Shows electricity kWh fees	Savings tracking	Supplier	Devices
Shelly scriptsshelly-porssisahko / Spot-hinta.fi	Script	✓	—	—	Any supplier	Shelly only
Home AssistantENTSO-E / Nord Pool + Shelly	Platform	✓	—	—	Any supplier	10,000+ devices
clever-PVDE	App	✓	—	—	Any supplier	Open (SG-Ready)
TibberSE / NO / DE / NL	App	✓	✓	✓	Must switch	~15 brands
VoltonEE	App	✓	✓	✓	Any supplier	Volton only
GridioEV charging · 27 EU countries	App	✓	✓	✓	Any supplier	BMW, Tesla, VW…
Elewatt25 countries *	App	✓	✓	✓	Any supplier	8 integrations *

Shelly scriptsshelly-porssisahko / Spot-hinta.fi

Type: Script
Device control: ✓
Shows electricity kWh fees: —
Savings tracking: —
Supplier: Any supplier
Devices: Shelly only

Home AssistantENTSO-E / Nord Pool + Shelly

Type: Platform
Device control: ✓
Shows electricity kWh fees: —
Savings tracking: —
Supplier: Any supplier
Devices: 10,000+ devices

clever-PVDE

Type: App
Device control: ✓
Shows electricity kWh fees: —
Savings tracking: —
Supplier: Any supplier
Devices: Open (SG-Ready)

TibberSE / NO / DE / NL

Type: App
Device control: ✓
Shows electricity kWh fees: ✓
Savings tracking: ✓
Supplier: Must switch
Devices: ~15 brands

VoltonEE

Type: App
Device control: ✓
Shows electricity kWh fees: ✓
Savings tracking: ✓
Supplier: Any supplier
Devices: Volton only

GridioEV charging · 27 EU countries

Type: App
Device control: ✓
Shows electricity kWh fees: ✓
Savings tracking: ✓
Supplier: Any supplier
Devices: BMW, Tesla, VW…

Elewatt25 countries *

Type: App
Device control: ✓
Shows electricity kWh fees: ✓
Savings tracking: ✓
Supplier: Any supplier
Devices: 8 integrations *

* Countries: most EU day-ahead markets, plus Norway and Switzerland.

* Devices: Shelly, Shelly Price API, Daikin Onecta, Home Assistant, eWeLink (Sonoff), Nibe myUplink, Tuya / Smart Life (via Home Assistant), Samsung SmartThings (air conditioners and plugs), evcc.

Why Day-Ahead Spot Prices Make Automation Work

Across Europe, electricity is traded on day-ahead markets such as Nord Pool, EPEX SPOT and OMIE, and the results are published openly on ENTSO-E's transparency platform. Prices for the whole next day are known every early afternoon, giving automation tools more than ten hours of known prices before the cheapest overnight window even starts.

Combine published day-ahead prices with a smart meter and the appliances many homes already have — electric water heaters, heat pumps, EV chargers — and shifting consumption to the cheapest hours becomes a practical saving rather than a theoretical one.

The key difference

Elewatt is not an electricity supplier — you keep the one you have. To actually save, though, your contract must bill you at the spot price hour by hour (or per quarter-hour): a spot, dynamic or exchange-price contract. Many suppliers offer one. On a fixed price, shifting consumption won't lower your bill.

Shelly device schedule controlled by Elewatt spot price automation

Open-Source and Dedicated Apps: Different Tools for Different Users

The open-source Shelly scripts — particularly shelly-porssisahko and the Spot-hinta.fi scripts — are genuinely excellent: they update device schedules daily and cost nothing. The catch: they only cover Nordic and Baltic price zones out of the box. For a developer willing to adapt a script, they are still hard to beat.

The difference is everything that surrounds the scheduling: a dashboard for settings, savings history over time, filter rules like 'run at least 3 hours between 6 AM and 10 PM', and alerts when prices spike. Dedicated apps add this experience layer for households who want automation to just work — without reading documentation.

Open-source scripts are great if you...

• Are comfortable flashing firmware and editing config files
• Don't need a UI or savings history
• Want zero monthly cost and full local control

A dedicated app is better if you...

• Want to set it up in minutes without reading documentation
• Want to see how much you've saved month by month
• Want filter rules, notifications, and multiple devices in one place

What to Look for When Choosing

Whichever solution you consider, ask these five questions before committing:

Does it support your country's day-ahead price zone?

Does it work with your current electricity supplier, or do you need to switch?

Can you set minimum runtime rules — e.g. 'run at least 4 hours per day, but not between 6 and 8 AM'?

Does it track and show how much you've actually saved over time?

What is the real setup time? Hours of configuration or minutes?

Elewatt covers day-ahead spot markets across Europe

No supplier switch needed. Works with your existing Shelly devices. Set filter rules, track savings, get notifications. Free to start.

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