# Epex Client

The *Epex Client* package provides access to the latest European Power Exchange (EPEX) market data **across all areas**.
It is intended primarily for hobbyist solutions.

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<table>
  <tr>
    <td style="vertical-align: top;">
      <img src="./docs/table.png" alt="Market Prices" width="350"/>
    </td>
    <td style="vertical-align: top;">
      <img src="./docs/bars.png" alt="Market Prices" width="450"/>
    </td>
  </tr>
</table>

## Overview

The **European Power Exchange (EPEX SPOT)** is a [market platform](https://www.epexspot.com/) for 
the trading of electricity in Europe. 
It provides a marketplace for electricity producers, consumers, and traders to buy and sell electricity, 
aiming to create a transparent and efficient market for power trading. 

The *Epex Client* package gives you access to the EPEX Spot Day-Ahead Market, where the electricity price and volume
for each hour of the next day is established.
You can work with these Day-Ahead prices by adjusting your electricity consumption patterns based on the price 
fluctuations. Here's how:

- **Shift High Consumption Activities**: reduce energy costs by scheduling energy-intensive activities (like running washing machines, dishwashers, or electric heating) during hours when electricity prices are lower.
- **Use Home Automation**: home automation systems or smart appliances can automatically adjust the timing of electricity usage based on the predicted lower-cost periods provided by the Epex-client.
- **Energy Storage**: energy storage systems (like batteries) can store electricity during low-price hours and use it during peak-price hours.

## Installation

```sh
npm i @tvanlaerhoven/epex-client
```

or

```sh
yarn add @tvanlaerhoven/epex-client
```

## Usage

First create an Epex client, with optional configuration.
The `debug` property allows for extra logging during usage of the client.

```typescript
import * as Epex from '@tvanlaerhoven/epex-client';

const client = new Epex.Client({ debug: true });
```

### Accessing day-ahead market data

The day-ahead market data contains the established electricity prices and quantities for a selected region, 
based on supply and demand. As an example. the data for `MarketArea.Belgium` can be requested as follows:

```typescript
try {
    // Get today's hourly market data
    const data = await client.getDayAheadMarketData(Epex.MarketArea.Belgium, Epex.today());
    console.log(`Today's electricity price from 9h-10h is €${data.entries[9].price}`);
} catch(error) {
    console.error(error.message);
}
```

The requested delivery date is passed as a string `"YYY-MM-DD"`, or using the convenient methods `Epex.today()` and
`Epex.tomorrow()`. 
Note that prices for the next day are typically available **in the early afternoon** on the day before delivery.

### SDAC (Single Day-Ahead Coupling), Great Britain and Switzerland

Most European countries are part of the **SDAC (Single Day-Ahead Coupling)** pan-European market coupling initiative,
which allows cross-border electricity trading and price convergence.
Since Brexit, **Great Britain** has its own market, and also **Switzerland** as a non-EU country is not part of the
SDAC initiative. For both regions it is necessary to pass the auction name when requesting Day-Ahead prices:

```typescript
const gbData = await client.getDayAheadMarketData(
    Epex.MarketArea.GreatBritain, 
    Epex.tomorrow(), 
    Epex.today(), 
    DayAheadAuction.GB_DAA1
);

const chData = await client.getDayAheadMarketData(
    Epex.MarketArea.Switzerland, 
    Epex.tomorrow(), 
    Epex.today(), 
    DayAheadAuction.CH
);
```

## Displaying market data in a browser

The Epex website does not allow browser requests from any other location than its own host 
([CORS](https://en.wikipedia.org/wiki/Cross-origin_resource_sharing)). To solve this, run a local
proxy server that drops any CORS headers from the http request.

```typescript
import * as Epex from '@tvanlaerhoven/epex-client';

const client = new Epex.Client({ proxyServer: 'http://localhost:8088', debug: true });
```

The [example](https://github.com/tvanlaerhoven/epex-client/tree/main/example) demonstrates this. Try it by running:

```sh
npm run example
```

The output is a page where you can choose to either visualize today's market prices in table or as a bar graph.