For example like this?
set @kWh_sum = 0;
SELECT
timestamp,
(@kWh_sum := @kWh_sum + kWh) as kWh_SumUp,
kWh
FROM
energi_portal.el_import
WHERE
timestamp BETWEEN ‘2020-01-11 00:00:00’ AND ‘2020-01-12 00:00:00’
ORDER BY timestamp DESC;
With the result:
timestamp,kWh_SumUp,kWh
“2020-01-11 00:00:00”,0.20,0.2
“2020-01-11 00:05:00”,0.40,0.2
“2020-01-11 00:10:00”,0.60,0.2
“2020-01-11 00:15:00”,0.90,0.3
“2020-01-11 00:20:00”,1.20,0.3
“2020-01-11 00:25:00”,1.70,0.5
…