By default the “Live Production” graph has the energy used and energy generated graph traces filled and the power used and generated traces are just thin lines. To me this is the opposite of what it should be. Filling indicates that the area under that curve is important, this is true for power, but not energy.
Is there a way to reverse this graph style?
Instantaneous Power
The instantaneous power, represented by an green line on the graph, is the power generated by the system at that moment in time. Measured in watts (W)
Energy
The energy, represented by a light green area on the graph, is the energy generated by the system up to that point in time for the current date. Measured in kilowatt hours (kWh)
I would say that power recorded at one interval on 5 mins is not as important as the amount actually used in those 5 minutes.
to reverse the graph you could reverse how your are importing the data ie swap v1 and v2 around and v3 and v4 and see what happens… im sure it will create issues with other calculations but your graph should show how you want
Hi,
Plotting POWER on the vertical axis and TIME on the horizontal axis leads to the situation where the area under the resultant curve is the ENERGY produced ( or an approximation based on the update interval ). This also follows mathematically if you step into the world of calculus.
B-Man is quite correct when he states that:
The instantaneous power, represented by an green line on the graph, is the power generated by the system at that moment in time. Measured in watts (W)
Ultimately what should matter most is the total energy generated ( transformed ) by the inverter and not what the output power might be at a given moment in time.
The closest analogy is a car’s speedometer ( speed ) vs odometer ( distance ). The car will hopefully get you from Point A to Point B, a fixed distance. Varying the speed may get you there sooner or later.
Yes, and it is the mathematically correct way to represent total energy. Like this example:
Which in this case shows grid import, with the line at the top being the power value and the shaded area = energy.
Area charts suggest the area shaded is representative of some volumetric quantity (an integral, in this case the integral of power over time).
In the case of shading the area under a cumulative energy value, the shaded area is meaningless. In this case the shading is being used simply as a way to visually distinguish it from other line plots.
Cumulative sum plots are usually shown as lines or discrete columns which distinguishes them from area plots so as to avoid this confusion.
Could reverse the graph by changing the way I upload data as you suggest, but that would mess up cost calculations etc. Thanks for the suggestion.
Sounds like you agree with me wattmatters, do you know of any way to get this modified on pvoutput.org?
I agree with you that use of an area chart implies the filled area has physical meaning - it’s the integral of the metric which is changing with time. e.g. in Fronius Solarweb daily charts the area under the power lines (be it generation or consumption) is what gets filled in, and that makes sense because the integral of power over time is energy.
In PVO the area under the cumulative energy line gets filled in and the integral of cumulative energy over time has no physical meaning. Cumulative energy already is the integral.
When plotting a cumulative value it shouldn’t really be plotted as an area. But we’ve all done it before I’m sure.
That PVO has chosen to use an area plot for cumulative energy values as a way to visually distinguish it from the power line is something I’m not going to lose sleep over. I know what the individual plots mean.
I have no solution as changing the chart types is something I think would need to be embedded into the system.
I agree. Not the end of the world.
