power

README

power

Utilities for querying power prices

This is a proof of concept (and probably way to abstracted for that, I got a little carried away, so it might change in time) on how to fetch by-the-hour power prices from your electrical company in Denmark.

Use it as inspiration, or simply run (go run cmd/main.go) or build and run (go build -o power cmd/main.go && ./power) to get some JSON out that you can feed to Influx or whatever.

Example utility

The example program in cmd will fetch upcoming by-the-hour prices and correlate them with official tariffs for your power meter (which varies a lot in DK, and depends on who delivers your power to your house), and spit out some JSON with your by-the-hour power price, broken into taxes and tariffs, etc.

This assumes, of course, that your power plan has by the hour pricing. I have no idea what happens if you don't, but I'd think you'd just get a list of identical data :)

Example REST server

There's also an example of a bare bones REST server in the server directory. Check the code there to see how it works, endpointsn (there's one) and such.

Prerequisites

Go to https://eloverblik.dk, and log in with NemID. Obtain an API Token from their web interface, and copy that to the config file (check power.conf.example). While you're there, note your measurement point ID, an 18-digit number identifying your power meter, in the same config file.

If you have more than one meter and/or are a power producer (like, if you have solar cells or a windmill, or whatever), results are somewhat unpredictable. Tariffs are tied to a specific metering point, and depending on wether that's a consumption or production point, tariffs vary. So if that's the case, find out which meter is your main consumption meter and use that. And even then, results might be unpredictable. I've seen configurations with multiple consumption meters each having different tariffs attached... Also, if you have reduced power tax for whatever reason (e.g. electric heating), I don't know what'll happen (but prices will probably be somewhat off).

Running

The app accepts a -c option, which will tell it which config file to read. Default is power.conf. It also accepts a -h option, which is the number of hours in the future to get prices for. The default is to get for the next 12 hours.

Output options

• -p Pretty print/indent JSON output.
• -s Print simple data, only time period and total price per kWh.

Caveat

On weekends, the source prices are only reported in EUR. They're then retroactively updated with the DKK price the following Monday, but it means that DKK prices, that are accurate/official, are not available during weekends. The code will try and compensate by extrapolating the last known exchange rate (from the preceeding Friday at 23:00) during weekends, and while the results are probably reasonably close, there's no guarantee they'll be exactly correct.

Blame Nord Pool for this.

Possible further features

• Consumption summary in kWH and DKK

Documentation

Index

• Variables
• func Prices(from, to time.Time, c interfaces.Configurator, ignoreMissingTariffs bool) ([]entities.FullPrice, error)
• type FullPrices
  • func Summarize(spot interfaces.SpotPricer, t interfaces.Indexer) FullPrices
  • func (fp FullPrices) InRange(from, to time.Time) bool
  • func (fp FullPrices) Price(t time.Time) float64
  • func (fp FullPrices) Range(from, to time.Time) FullPrices

Variables

var ErrEloverblik = errors.New("error getting data from eloverblik.dk")

Functions

func Prices

func Prices(from, to time.Time, c interfaces.Configurator, ignoreMissingTariffs bool) ([]entities.FullPrice, error)

Prices fetches price data from `from` and as far ahead as they're available, for the given `mid` using the `token` for auth. If 'IgnoreMissingTariffs' is true, just return spot prices without tariffs, if they can't be fetched.

Types

type FullPrices

type FullPrices struct {
	Contents []entities.FullPrice
	From     time.Time
	To       time.Time
}

var FullPricesCached FullPrices

func Summarize

func Summarize(spot interfaces.SpotPricer, t interfaces.Indexer) FullPrices

Summarize will combine the information in spot and t into a list of FullPrices

func (FullPrices) InRange

func (fp FullPrices) InRange(from, to time.Time) bool

InRange returns true if fb contains data in the full range from - to

func (FullPrices) Price

func (fp FullPrices) Price(t time.Time) float64

Price implements the Pricer interface

func (FullPrices) Range

func (fp FullPrices) Range(from, to time.Time) FullPrices

Range returns the subset of fp that are between from and to. If out of range, returns empty