I was told by Niclas at FooGadgets that I need to multiply by 60 to convert from Watt-minute to Watt-hours:

------------------------- From Niclas ---------------
Pmomentan = Temp*10/1000*60*60/(Time_now - Time_previous)
Temp är inkomna temperaturen
60/(Time_now - Time_previous) är en faktor som behöver läggas till eftersom varje blinkdetektor har olika sändningsintervall. Det skiljer sig med kanske +-2 sekunder. Intervallet är också beroende på batterispänning och chipets temperatur. Resultat i kW
-------------------------
I've skipped adjusting for the +-2 seconds since I instead interpolate into 60 one-minute values pr. hour based on what ever was logged. Quite often several reading are missing. Either because of a sensor collision (two sensors sending via RF at the same time can cause Tellstick to miss the value) or just some other issue.

I am supposed to receive 60 values pr. hour by they vary from as low as 49 to 59 at best.

That is what I do. The user can specify Wh pr. "blink" on the settings page (usually 1).

The "sum" below the graph is the sum of all the 1-minute temp values * whPerBlink * 10 * 60 / 1000

The *10 is because the energy meter reports blinks/10 (so temp of 2.4 means 24 blinks last minute).

I've changed the lables from kWh to kW and redeployed on tellmon.net
Do you still get the error on tellmon.net?

But how can I calculate the consumed energy in kWh? I though that simply adding all the Wh-values would be correct. 

That's what is supposed to happen when it works. But we wanted it to crash like earlier.

That's strange. Does it work when you click on the sensor to see the graph in the normal way (but on test.tellmon.net) as well?

Can you please try again but using test.tellmon.net instead of tellmon.net.

Logon to http://test.tellmon.net
Then open a new tab and try this URL:
http://test.tellmon.net/services/telldus.svc/GetSensorDataForGraph?sensorId=1332439&graphRange=Day

I have enabled more logging and diagnostics as well as running test.tellmon.net in debug mode. Hopefully that will give me some pointers to why you are having this issue.

You should get some more text below the "Request error" this time.

Is it only for the energy meter, or do other sensors also fail?

Can you please logon to http://tellmon.net then open the following URL in another tab in the same browser?
http://tellmon.net/services/telldus.svc/GetSensorDataForGraph?sensorId=1332439&graphRange=Day

Thank you

That's strange. Can't find any errors in the log files. Do you still get the 400 bad request? 

Can you try again now? I have modified the formula to show kWh.