Just the other day I checked my ADSL2 volume usage for the first time in a couple of months and noticed it had quite a high "idle level". That is, in the hours I wasn't home there was consistent data traffic at a higher rate than I expected, it was 1.45mb/hr. Only fluctuating by 0.02mb/hr at the most. This meant my idle rate was sitting at about 1 gig/month!
Then when the power was cut for 4 hours so the UPS's got to the point of shutting the observatory PC down, I noted the idle rate went down to 0.02mb/hr.
No fault of D Weather, when I installed it I asked it to refresh the weather information on a regular basis. I think it was 15mins or 30mins.
Turns out it was D Weather refreshing it's weather information and I had forgotten about that feature. I have now disabled it's refreshing seeing as I don't use it often and when I do I click refresh anyhow.
The things you don't necessarily notice/realise!