SELECT  Dev_ID, 

	DATETIMEFROMPARTS(YEAR(TS), MONTH(TS), DAY(TS), DATEPART(HOUR, TS), 0, 0, 0)    AS [TS]
	,Max([ActEnergy_Pos]) maxActEnergy_Pos
	,Min([ActEnergy_Pos]) AS minActEnergy_Pos
	,(Max([ActEnergy_Pos]) - Min([ActEnergy_Pos]))SumActEnergy 
						
FROM [dbo].[t_Input]

WHERE   (TS BETWEEN '2019-02-11' AND '2019-02-12') and ActEnergy_Pos > 0 and Dev_ID = 1
group by DATETIMEFROMPARTS(YEAR(TS), MONTH(TS), DAY(TS), DATEPART(HOUR, TS), 0, 0, 0) , Dev_ID
ORDER BY TS

SELECT * FROM
(
SELECT 
TS, Dev_ID, maxActEnergy_Pos as max_val, 
LAG(maxActEnergy_Pos,1,0) OVER (ORDER BY TS) as min_val, 
maxActEnergy_Pos - (LAG(maxActEnergy_Pos,1,0) OVER (ORDER BY TS)) as diff
FROM
(
SELECT  Dev_ID,
	DATETIMEFROMPARTS(YEAR(TS), MONTH(TS), DAY(TS), DATEPART(HOUR, TS), 0, 0, 0)    AS [TS]
	,Max([ActEnergy_Pos]) maxActEnergy_Pos
				
FROM [dbo].[t_Input]

WHERE   (TS BETWEEN '2019-02-10 23:00' AND '2019-02-12 01:00') and ActEnergy_Pos > 0 and Dev_ID = 1
group by DATETIMEFROMPARTS(YEAR(TS), MONTH(TS), DAY(TS), DATEPART(HOUR, TS), 0, 0, 0) , Dev_ID
) as t
) as t2
WHERE (TS >= '2019-02-11' AND TS <'2019-02-12')
ORDER BY TS

declare @t table (dt datetime, v int);
insert into @t
values
 ('20190101 10:00:01', 1), ('20190101 10:01:01', 2), ('20190101 10:02:01', 3),
 ('20190101 11:00:01', 6), ('20190101 11:02:01', 7), ('20190101 11:03:01', 8);

select
 b.dth,
 min(a.v), max(a.v),
 max(a.v) - min(a.v)
from
 @t a cross apply
 (select dateadd(hour, datediff(hour, '1900', a.dt), '1900')) b(dth)
group by
 b.dth;

select
 b.dth,
 min(a.v), lead(min(a.v), 1, max(a.v)) over (order by b.dth),
 lead(min(a.v), 1, max(a.v)) over (order by b.dth) - min(a.v)
from
 @t a cross apply
 (select dateadd(hour, datediff(hour, '1900', a.dt), '1900')) b(dth)
group by
 b.dth;