Excel: Calculate average daily usages of gas based on date and time

Question

awkward question to word. I'm using Excel and would like to calculate the average usage of gas in my house. I have got a list of times and dates which I write down when I get chance or remember, is there a good way to do this?

I would like to use cell formulas by the way.

An example of the data I have to work with:

  Date/Time         Gas   Electric
25/01/15 01:48    £10.62    £3.38
                           +£5.00
26/01/15 01:48    £8.56     £6.92
26/01/15 02:00    £8.18     £6.45
27/01/15 13.19    £7.44     £6.03
27/01/15 18.00    £7.06     £5.57
27/01/15 19:50    £7.06     £5.41
27/01/15 21:14    £6.97     £5.26

Edit: Using TriHard8's answer, this is what is produced

Does this mean that 0.70 pence is used each hour based on the two times?

Edit 2: Still getting negative numbers :S

Answer 1

Gas used between 2 dates/times divided by ((Date2 + Time2) - (Date1 + Time1)). (10.62 - 8.56) / ( (26/01/15 + 01:48) - (25/01/15 + 01:48) )

Put this formula into H6: =( F5 - F6 ) / ( (D6+E6) - (D5+E5) ) This will be use per day. It doesn't matter if you compare 2 measurements from the same day, or over 20 days, it will be the average per day.

You need to make sure that you format the resulting cell to be a number, with whatever precision you'd like.