Google PowerMeter and sample C# .Net API usage

Update 2001-06-25
A lot of people still contact me about this project. I received this mail today, just in case you’re getting interested by the project, you should know that it will die pretty soon:

Dear PowerMeter User,

We first launched Google PowerMeter as a Google.org project to raise awareness about the importance of giving people access to their energy information. Since our launch, there’s been more attention brought to this issue, and we’re excited that PowerMeter has helped demonstrate the importance of access to energy data. However, our efforts have not scaled as quickly as we would have liked, so we have decided to retire PowerMeter.

You will continue to have access to the product until September 16, 2011, after which time you will no longer be able to access your PowerMeter account. We know that having access to your energy information has helped you save energy and money. There are many options available for you from our device and utility partners. Please visit this page to learn more: http://www.google.com/support/powermeter/bin/answer.py?hl=en&answer=1342532

We also understand that having your historical energy data is important to you. We’ve made it easy for you to download your data. To export your PowerMeter data to a CSV (Comma Separated Values) file, log in to your account and go to “Account Settings.” More information can be found here: http://www.google.com/support/powermeter/bin/answer.py?hl=en&answer=164264

We appreciate your understanding and hope that you’ve enjoyed using Google PowerMeter. If you have questions about this announcement, please visit our FAQ pages at http://www.google.com/powermeter/about/faqs.html

Thank you,
Google PowerMeter team

© 2011 Google Inc. 1600 Amphitheatre Parkway, Mountain View, CA 94043

You’ve received this mandatory service announcement email to update you about important changes to your Google PowerMeter account.

Google PowerMeter offers you to collect your home’s / enterprise’s / specific equipment’s power usage and have some basic analysis on it.

There’s also a Google PowerMeter API so that everyone can build devices able to report their consumption and applications.

I would say one cheap and evolutive way to implement this API would be to use a Z-Wave power meter and have a Z-Wave central controller sent the data to Google servers. It could quickly get interesting because this could make you know the exact consumption of all your lights by calculating the result of the light-on/light-off order on individual lights. And this could even lead to define some max energy consumption scenarios so that you don’t allow more than X watts for all the lights of your house (this is just a idea, I would never put this in my home).

I know this isn’t the next BIG thing. Because everyone knows it’s all about the social right-now. But still, I think this could be the most green project of all time. Because it clearly shows people (or enterprises) how they consume energy and gives the useful analysis to find solutions. And for once it doesn’t try to make you feel guilty about not being green enough, it just brings facts.

By the way, you can have a negative energy consumption (power meter counting backward) in Google PowerMeter. I don’t think this is a bug, it must be for people selling their energy for their solar or wind energy producer equipments. But unfortunately you set the estimated cost of energy but you can’t set its estimated revenue price.

Sample API call

Here is a sample Google PowerMeter API call in C# .Net :
I just changed a little bit of the authentication parameters so that you can’t actually upload data on my account.

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using System;
using System.Globalization;
using System.IO;
using System.Net;
using System.Text;
using System.Threading;
 
/* Equipment was activated with this URL :
 * https://www.google.com/powermeter/device/activate?mfg=WebIngenia&model=TestEquipment1&did=100102030405&cvars=1&dvars=0&rurl=http://test.webingenia.com/powerMeter&snonce=123
 *
 * The resulting request was (available here : http://test.webingenia.com/read/powerMeter#id2473 ) :
 * $_POST = array(
 *		[snonce] => 123
 *		[hash] => _____6c2562aeb7bab4e24afc7beeb18c701c04ba,____8c9f62fa8a137eba7fa35b5f58802fca2e56,____f4db13304c49d36fb81b20cabbe147f8ce34
 *		[token] => ________FhCtzebg_P____8BGMWjtUs
 *		[path] => /user/____4578579014915368/____4578579014915368/variable/WebIngenia.TestEquipment1.100102030405
 * )
 *
 */
 
namespace test {
	class Program {
 
		private static readonly Random _random = new Random();
 
		public const String DeviceHash = // Useless
			"____bf8262aeb7bab4e24afc7beeb18c701c04ba,____8c9f62fa8a137eba7fa35b5f58802fca2e56,____f4db13304c49d36fb81b20cabbe147f8ce34";
 
		public const String DeviceToken = // Needed for authentication
			"________FhCtzebg_P____8BGMWjtUs";
 
		public const String DevicePath = // URL of the device
			"/user/____4578579014915368/_____4578579014915368/variable/WebIngenia.TestEquipment1.100102030405";
 
		public const String DeviceVar = "c1";
 
		public const String FeedUrl = // URL of the Google PowerMeter API
			"https://www.google.com/powermeter/feeds";
 
		public const String EventUrl = // URL where to send the data
			FeedUrl + "/event";
 
		public const int Period = 5000; // 5 to 10 seconds
 
 
		static double MeterValue {
			get {
				return Settings.Default.MeterValue;
			}
			set {
				Settings.Default.MeterValue = value;
				Settings.Default.Save();
			}
		}
 
		static void Send() {
 
			// We increment the counter (by 0 to 1 kWh)
			MeterValue += _random.NextDouble();
 
			Console.WriteLine( "MeterValue : {0}", MeterValue );
 
			// This is what we are going to send
			var strContent = String.Format(
			@"
<feed xmlns=""http://www.w3.org/2005/Atom"" xmlns:meter=""http://schemas.google.com/meter/2008"">
	<entry>
      <category scheme=""http://schemas.google.com/g/2005#kind"" term=""http://schemas.google.com/meter/2008#instMeasurement"" />
      <meter:subject>{0}</meter:subject>
      <meter:occurTime meter:uncertainty=""1.0"">{1}</meter:occurTime>
      <meter:quantity meter:uncertainty=""0.001"" meter:unit=""kW h"">{2}</meter:quantity>
    </entry>
</feed>",
				FeedUrl + DevicePath + "." + DeviceVar,						// Device URL
				DateTime.UtcNow.ToString( "yyyy-MM-dd'T'HH:mm:ss.fffK" ),	// Current UTC date
				MeterValue.ToString( CultureInfo.InvariantCulture )			// Meter value
			);
 
			// We convert it into raw content
			var content = Encoding.UTF8.GetBytes( strContent );
 
			// We create the POST request
			var req = WebRequest.Create( EventUrl );
			req.Headers.Add( "Authorization", "AuthSub token=\"" + DeviceToken + "\"" );
			req.Method = "POST";
			req.ContentLength = content.Length;
			req.ContentType = "application/atom+xml";
 
			try {
				// Opening the request stream means starting the request
				Console.Write( "Requesting..." );
				using ( var requestStream = req.GetRequestStream() ) {
 
					// We send the content
					requestStream.Write( content, 0, content.Length );
 
					// And we end the request by getting the response
					using ( var streamReader = new StreamReader( req.GetResponse().GetResponseStream() ) ) {
						Console.WriteLine( "Result : " + streamReader.ReadToEnd() );
					}
				}
			}
			catch ( WebException e ) { // If a webException occurs (should be 400)
				// We display the error
				var response = e.Response as HttpWebResponse;
				if ( response == null ) // This is not the exception that we want
					throw;
				using ( response ) {
					using ( var responseStream = response.GetResponseStream() ) {
						Console.WriteLine(
							"Error {0} : {1} ",
							response.StatusCode,
							new StreamReader( responseStream ).ReadToEnd()
						);
					}
				}
			}
		}
 
		static void Main() {
			while ( true ) {
				try {
					Send();
				}
				catch ( Exception ex ) {
					Console.WriteLine( "Exception : " + ex );
				}
				Thread.Sleep( Period + _random.Next( Period ) );
			}
		}
 
		// This code was generated by Visual Studio (but I prefer to put it here rather than having to publish the VS project)
		#region Auto-generated
		[System.Runtime.CompilerServices.CompilerGeneratedAttribute()]
		[System.CodeDom.Compiler.GeneratedCodeAttribute( "Microsoft.VisualStudio.Editors.SettingsDesigner.SettingsSingleFileGenerator", "9.0.0.0" )]
		internal sealed class Settings:System.Configuration.ApplicationSettingsBase {
 
			private static Settings defaultInstance = ( (Settings) ( Synchronized( new Settings() ) ) );
 
			public static Settings Default {
				get {
					return defaultInstance;
				}
			}
 
			[System.Configuration.UserScopedSettingAttribute()]
			[System.Diagnostics.DebuggerNonUserCodeAttribute()]
			[System.Configuration.DefaultSettingValueAttribute( "3000" )]
			public double MeterValue {
				get {
					return ( (double) ( this[ "MeterValue" ] ) );
				}
				set {
					this[ "MeterValue" ] = value;
				}
			}
		}
		#endregion
	}
}

I didn’t let it running too much time but still you can see that it works :

2 thoughts on “Google PowerMeter and sample C# .Net API usage”

  1. Heyy…Thanks for the great post!!…really helped me understand and use the Google Power Meter.

    I tried running my code, in the response it gave an error saying “Invalid Path Term” reason: PM400-31

  2. Hi Florent,
    you have written a great blog and have make understand Google Power Meter Development very awesome .. . as i have found some help regarding development GPM from some other side as well but they all were by using Python Api can you please Help me for getting data from power meter using C API please share me code my id(mohsin4real@yahoo.com)

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