Math Help - Analysis of time-series data

Hi,

Firstly - sorry if this is the wrong place to post this, but I need help! Been a long time since I have had to do any maths so I appreciate any help you can give.

I have been collecting electricity usage data from 6 households over a period of 28 days via use of a home energy monitor. This has allowed me to collect 1440 pieces of data per day per household.

So far I have collated my data to half-hour portions allowing me easy graphic representation.

Next (and importantly) I need to identify how much energy usage has changed over the period of 28 days, either overall or in comparison to the first week of data.

What I want to identify is that they are either reducing their energy usage or maintaining their energy usage but with so many ups and downs its hard for me to gauge a way to represent this!

Any help would be very much appreciated... any tips on statistical methods or graphical representations.

P.s. attached a few examples of the graphs I have made