CheapPower module

[dr-m]

This fetches electricity prices and chooses the cheapest future time slot. Currently, the only data source is the Nordpool prices for Finland, as provided by ENTSO-E and https://sahkotin.fi. To use:

• copy cheap_power.tapp to the file system
• Invoke the Tasmota command CheapPower1, CheapPower2, … to
• download prices for the next 24 to 48 hours
• automatically choose the cheapest future time slot
• to schedule Power1 ON, Power2 ON, … at the chosen slot
• to install a Web UI in the main menu
• For a full installation, you will want something like the following:

Backlog0 Timezone 99; TimeStd 0,0,10,1,4,120; TimeDst 0,0,3,1,3,180

Backlog0 SwitchMode1 15; SwitchTopic1 0
Backlog0 WebButton1 boiler; WebButton2 heat
PulseTime1 3700

Rule1 ON Clock#Timer DO CheapPower1 ENDON
Timer {"Enable":1,"Mode":0,"Time":"18:00","Window":0,"Days":"1111111","Repeat":1,"Output":1,"Action":3}
Rule1 1
Timers 1

The download schedule can be adjusted in the timer configuration menu. The prices for the next day will typically be updated in the afternoon or evening of the previous day.

In case the prices cannot be downloaded, the download will be retried in 1, 2, 4, 8, 16, 32, 64, 64, 64, … minutes until it succeeds.

The user interface in the main menu consists of 4 buttons: ⏮ moves to the previous time slot (or wraps from the first to the last) ⏯ pauses (switches off) or chooses the optimal slot 🔄 requests the prices to be downloaded and the optimal slot to be chosen ⏭ moves to the next time slot (or wraps from the last to the first)

The status output above the buttons may also indicate that the output is paused until further command or price update:
⭘
It may also indicate the start time and the price of the slot:
⭙ 2024-11-22 21:00 12.8 ¢

I am using this for controlling a 3×2kW warm water boiler. For my usage, 1 hour every 24 or 48 hours is sufficient.

Description:

Related issue (if applicable): fixes #

Checklist:

• The pull request is done against the latest development branch
• Only relevant files were touched
• Only one feature/fix was added per PR and the code change compiles without warnings
• The code change is tested and works with Tasmota core ESP8266 V.2.7.8
• The code change is tested and works with Tasmota core ESP32 V.3.1.0.241117
• I accept the CLA.

NOTE: The code change must pass CI tests. Your PR cannot be merged unless tests pass

[s-hadinger]

Thanks. Is it valid only for Finland? If so, I believe it should show in the name of the file like "cheap_power_Finland"

[dr-m]

Thanks. Is it valid only for Finland? If so, I believe it should show in the name of the file like "cheap_power_Finland"

The current version is useful only for Finland, but it could be fairly easily extended to cover at least the entire Nord pool area. The data is produced by ENTSO-E, which based on https://transparency.entsoe.eu/load-domain/r2/totalLoadR2/show seems to cover most of Europe, including Türkiye and Ukraine. Some of these countries might not implement dynamic pricing for end consumers yet, but I believe that it will come.

Ideally, someone would run a public service that is based on some code like https://github.com/oysteinjakobsen/fetch-day-ahead-price or https://github.com/JaccoR/hass-entso-e so that end users can save themselves the trouble of registering and configuring an API key with ENTSO-E. Besides, this API could be too resource intensive to implement in Tasmota.

The hypothetical service would deliver the known prices starting from the currently active slot in a uniform format. The command would take a parameter to the command to specify the price area (such as an area of Norway):

CheapPower2 NO4

This could be translated into a simple URL like http://e-prices.example.com/no4 or http://no4.e-prices.example.com if such a service existed, or it could use country specific services (see below). I’d prefer HTTP instead of HTTPS, because SSL and TLS are constantly evolving, which could require frequent firmware updates.

The second parameter could also be a full URL, for example pointing to server in the LAN, which could run an ENTSO-E interface and cache to serve multiple devices. This would in no means be limited to ENTSO-E or Europe.

Another thinkable enhancement would be a third parameter to specify the desired number of slots to choose per day, like this:

CheapPower1 DE 5

Some heating could need to run for multiple hours per day. There are some plans to narrow the price slots from 60 to 15 minutes in the future. In that case, even my deployment would require 2 to 4 such slots per day.

A quick search turned up some further open JSON data sources:

• Sweden: https://mgrey.se/espot/api
• Norway: https://www.hvakosterstrommen.no/strompris-api
• Denmark: https://www.elprisenligenu.dk/elpris-api

These could be implemented fairly easily, after asking the operators if this kind of automated access is okay with them. The format of the URL and the data would likely vary between any area-specific JSON data sources. I realize that to reduce the memory footprint, it could make sense to split this interface into separate modules that would be loaded on demand.

For Estonia, I only found https://elektrihind.ee/borsihind/ which does not seem to include any public JSON based interface. The German Fraunhofer-Institut für Solare Energiesysteme is running https://energy-charts.info/charts/price_spot_market/chart.htm with a nice country selection, but apparently without any raw data interface that is suitable for this kind of use. There is a CSV export function that seems to spit out data for the current week.

I think that this needs to start somewhere. If it helps, I can make the country parameter mandatory in the first version, and reject anything else than FI. Possibly I could refactor the parsing and implement dynamically loaded parser for two data sources, one of them being the FI data source.