Solar forecast: switch from power at time to energy during period

[andig]

For solar forecasts, we currently expect production power at timestamp. This requires 25 data points for a day. Having caused confusion before (https://github.com/evcc-io/evcc/issues/22979), we might better switch to energy during period and produce power for charts by interpolating.

TODO

• [ ] gather and update affected tariffs
• [ ] figure out where we're using this (optimizer, solar forecast, solar forecast scaling...)

[tantive]

Not sure if I undstand/like that idea. Supported solar forecast suppliers like open-meteo are very good in estimating power - even in 15-min intervals. By using a more coarse grained energy value and trying to estimate power values unnecessary error/deviation is introduced.

Can you provide details on "requires 25 data points for a day"? With hourly energy values you are reducing that to 24.

[premultiply]

Does not make any difference. Its just another mathematical representation of the same for easier calculation. At the end all forecasts return a "mean power over interval" which is the same as energy. The is no such thing as power generated at exactly 12:00:00.000. That would be horribly inaccurate and always requires an interpolation between two samples to get a value for all times in between. And the mean value of this linear interpolation is: energy during time window between two samples.

07:00: 0.5 kW 08:00: 1.5 kW 09:00: 3.0 kW

07:00-08:00: 1.00 kWh 08:00-09:00: 2.25 kWh

[tantive]

Understood, thanks for the clarification. Ping me if i can contribute in switching open-meteo support to 15-minute intervals and/or energy during time window.