Add nth hour attribute to sensor

[jjguti]

Adds an attribute of the price "rank" of the current hour in the day. It makes it easy to write automations that get triggered on the i.e. "5 cheapest hours on the day", "the 3 most expensive hours of the day" and so on.

[stigvi]

This is a good idea. But still, how useful is it? If I want to charge my car on the N number of cheapest hours, I usually want to do that between 16:00 when I am home from work and to 07:00 next day. But my car won't be charged at all if the cheapest hours is before 16:00. And you make an artificial split at midnight even if prices are available the next day, too. So this sensor could indicate a lot of cheap hours before midnight, but there are even cheaper hours after midnight when the car is finished charging.

But I still think your idea is good, but I would want a configurable time frame so that I could find the cheapest hours between a time this day and a time next day.

[jjguti]

Sure, I understand what you mean. My use case is slightly dfferent, I want to warm the house on the cheapest hours of the day and for that this sensor is very useful (since the house unlike the car is always there).

Sure we could go over midnight but that introduces some problems too, I think. For example what happens if the hours for the next day change the distribution of cheap hours? We could end up with many more or less cheap hours than we want.

My $0.02

[stigvi]

I liked your idea so much that I have already implemented it on my own system. I am not using this Nordpool integration much so it is implemented in pyscript. I append the tomorrow list to the end of the today list and then select the 24 prices from 14:00 to 14:00 next day. This is sorted and I set the value on a nth_cheapest_hour_1414 sensor.

And I do the same for a nth_cheapest_hour_1605 sensor, but select the prices from 16:00 to 05:00 before sorting.

Prices are read from Nordpool usually between 13:00 and 14:00 so I think my time period from 14:00 to 14:00 is less affected by price changes than a midnight to midnight sensor.