C1=1 - first positive value is subtracted from all subsequent values

Questions
#1

Hi,

I am uploading solar data to PVOutput every 5 minutes using the addstatus API with c1=1. My inverters (Victron MPPT) reset the daily yield to 0 at midnight. Uploads start at 05:30.

Observed behavior today (01/06/2026):

From 05:30 onwards, the inverters report v1=0 – PVOutput correctly shows 0.000 kWh for all these uploads.

At 05:50, the first positive value is sent:

d=20260601&t=05:50&v1=10&v2=4&c1=1

PVOutput shows: 0.000 kWh instead of 0.010 kWh

From that point on, every value is exactly 10 Wh lower than what is sent:

|Time|Sent (Wh)|PVOutput shows|
| --- | --- | --- |
|05:50|10|0.000 kWh|
|06:40|20|0.010 kWh|
|07:05|30|0.020 kWh|
|08:05|70|0.060 kWh|

Key facts:

  • Uploads correctly started at v1=0 from 05:30 onwards
  • The inverter counts in 10 Wh steps (minimum resolution)
  • The first positive value (10 Wh) is consistently subtracted from all subsequent values
  • This results in the daily total being 10 Wh too low at end of day

My question: Is this expected behavior with c1=1? If the daily counter starts correctly at 0, why does PVOutput subtract the first positive value from all subsequent values?

Is there a recommended way to upload a daily cumulative energy value with 10 Wh resolution so that PVOutput displays it accurately?

Thanks in advance!

#2

Hi @adahmen,

c1=1 is used to indicate that both v1 and v3 are lifetime values rather than daily values.

https://pvoutput.org/help/api_specification.html#cumulative-energy

Grannos.

#3

Hi @grannos,

thank you for your answer.
So the correct way with daily resetted data is → not using c1 ?

Best regards,
Albert

#4

Yes, the “c1” option is for lifetime energy value that never expected to reset every day.

If you are sending 0Wh at the start of the day, don’t send c1 or set it to 0.