Average each hour's meter readings - excel

Question

I have two columns of data with five or six meter readings each hour:
time (HH:MM:SS) (C3:C103) meter readings (D3:D103).
I would like to average each hour's readings to condense the data down to one averaged meter reading per hour.
I tried =Averageif(C3:C103,Hour=10,D3:D103) but clearly have something wrong.

Answer 1

Assuming you have just time values in C3:C103 (not with dates) then you could get your results like this:
List the numbers 0 to 23 in F2 down then use this formula in G2 copied down
=AVERAGEIFS(D$3:D$103,C$3:C$103,">="&F2/24,C$3:C$103,"<"&(F2+1)/24)
That will give you a table with the results for each hour

Answer 2

You can do this with one formula.
The following is an Array formula (need to press Ctrl + Shift + Enter, instead of just Enter to add it), and works for anything in the 10 o'clock hour.
{=AVERAGE(IF(HOUR(C3:C55)=10,D3:D55))}
Again, type the formula without the curly brackets then hold down Ctrl + Shift then press Enter
Basically the formula looks at the hour of each entry, checks to see if it is 10, then averages the adjacent numbers if the previous condition is true.
ALTERNATIVE:
You don't need a formula at all, (or any helper columns) if you just use a pivot table.
Select your data
Add your time column to the Row Labels section of the pivot table
add your meter readings column to the values section
In the Pivot table right-click on the meter readings data and select Show Values As ... Average in the menu.
In the pivot table, right-click on the time data and select the group option. In the option box select Hours only, and click OK.
That will give you the average for each hour without any additional formulas. It's also nice because it requires little maintenance after you have created, other than refreshing each time you get new data.

Answer 3

solution for my comment earlier:
This is easily done with a pivot table. First, break down the HH:MM:SS column down into an hours column only (since you want it grouped by hours). Then put all of the data into a pivot table, and put the 'hours' column in the row labels, and the meter readings (make sure to do an average, not a count) in the values field. This should be what you need.