# \[Inspiration\] Daily energy prices chart (using Power by the Hour)

**URL:** https://community.homey.app/t/inspiration-daily-energy-prices-chart-using-power-by-the-hour/80821
**Category:** Flows
**Tags:** energy, homeyscript, flow, homey-pro
**Created:** [May 20, 2023, 2:42pm UTC](https://community.homey.app/t/inspiration-daily-energy-prices-chart-using-power-by-the-hour/80821 "2023-05-20T14:42:26Z")
**Posts on this page:** 1
**Showing post:** 1

<div class="post-metadata">

### Author: ![Stikstof](https://sea1.discourse-cdn.com/flex025/user_avatar/community.homey.app/stikstof/32/76870_2.png) [@Stikstof](https://community.homey.app/u/Stikstof)
#### Post date: [May 20, 2023, 2:42pm UTC](https://community.homey.app/t/inspiration-daily-energy-prices-chart-using-power-by-the-hour/80821/1 "2023-05-20T14:42:26Z")

</div>

Hi all. I’ve been working on a set of flows to create a chart of the energy prices of the next day (using the [Power by the Hour App](https://homey.app/en-us/app/com.gruijter.powerhour/Power-by-the-Hour)). When the new prices come in, the chart is generated and sent to myself in a notification. As I think it might be useful for others, I’d like to share my work with you.

# Chart

The chart itself looks like this (and is configurable), for which I use a free online tool called [Image Charts](https://www.image-charts.com/). With this tool, I can send the chart configuration encoded in the URL and it will return an image file of the chart. To fetch the image for use within a Homey flow, I use the [Image Grabber](https://homey.app/en-us/app/image.grabber/Image-Grabber/) app.

 ![Example chart](https://us1.discourse-cdn.com/flex025/uploads/athom/original/3X/b/2/b20654d78b711425a30a1f81ddaabcdb4e509fb5.png)

# How it works

1. _Power by the Hour App_ signals about new prices and returns “Prijzen” tag.
2. The _HomeyScript_ converts the prices object into an encoded URL for the chart and returns “ChartUrl” tag.
3. Fetch the image using the _Image Grabber App_
4. Send myself a notification with the fetched image.

# Flows

(note: the flow preview is showing a grey question mark instead of the actual tag used. Here the “ChartUrl” tag should be selected, which is set by the HomeyScript card)

# HomeyScript

```auto
// Check if args are set
if (!args[0]) return false;

// Set base url
const chartWidth = 540;
const chartHeight = 320;
const baseUrl = `https://image-charts.com/chart.js/2.8.0?bkg=white&height=${chartHeight}&width=${chartWidth}&c=`;

// Convert input data to prices, labels and values
const prices = JSON.parse(args[0].replaceAll("'", "\""));
const labels = Object.keys(prices).map((label) => {
  return label.padStart(2, "0");
});
const values = Object.values(prices);

// Map color of each bar based on value.
// You can play with the colors and values, if you like.
const backgrounds = values.map((value) => {
  if (value <= 0.15) {
    return 'rgb(189, 44, 188)'; // Purple (free energy)
  }

  if (value <= 0.25) {
    return 'rgb(0, 170, 101)'; // Green (relatively cheap)
  }

  if (value <= 0.3) {
     return 'rgb(53, 86, 81)'; // Dark green (normal price)
  }

  return 'rgb(237, 95, 23)'; // Orange (high price)
});

// Add a data label to the cheapest and most expensive hour
const cheapestIndex = values.indexOf(Math.min(...values));
const expensiveIndex = values.indexOf(Math.max(...values));

const datalabels = values.map((value, index) => {
  if (index === cheapestIndex || index === expensiveIndex) {
    return [`€${value.toFixed(2)}`];
  }
  return [];
});

// Build configuration for the chart
const settings = { 
	type: "bar",
	data: {
		labels,
		datasets: [
			{
				label: "Prijzen",
				backgroundColor: backgrounds,
				data: values
			}
		]
	},
	options: {
		responsive: true,
		legend: {
			position: "none"
		},
		layout: {
			padding: {
        top: 35,
        bottom: 0,
        left: 5,
        right: 5
      }
		},
		rectangleRadius: 6,
    plugins: {
      datalabels: {
        anchor: 'end',
        align: 'start',
        offset: -40,
        padding: 5,
        backgroundColor: backgrounds,
        color: 'white',
        borderWidth: 2,
        borderColor: 'white',
        borderRadius: 100,
        font: {
         size: 14
        }
	    }
    },
    datalabels
  }
}

// Build the final url and save as tag
const settingsUrl = encodeURIComponent(JSON.stringify(settings))
const fullUrl = baseUrl + settingsUrl;
await tag('ChartUrl', fullUrl);

log(fullUrl);
return true;

```

# Result

On iOS, long-press the notification to see the entire image. (You can also click on the notification, but then you’ll be redirected to the Homey app showing the image, which takes a second longer 😉 )

 ![Screenshot iPhone notification](https://us1.discourse-cdn.com/flex025/uploads/athom/original/3X/8/8/8875a0000e459c6e73f7c6d0d2ea873e34d58dda.jpeg)

# Final words

That’s it! I hope this gives some inspiration. Feedback, suggestions or improvement ideas are more than welcome! 🙂

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_[View the full topic](https://community.homey.app/t/inspiration-daily-energy-prices-chart-using-power-by-the-hour/80821)._