You start using next month's. see the section below the estimator on
this page.
In effect you can carry forward a full month's contracted units, either over or under.
Various scenarios all assuming you have contracted for 2 units:-
In month 1 you use 1.4 units. In month 2 you have 2.6 units available. However you can also eat into the month 3 units so have a total possibility of 4.6 units in month 2.
Let's say however in month 2 you only use 0.5 units of the possible 2.6. Of the remaining 2.1 units, you can only carry forward 2.0 into month 3. So the maximum of contracted plus carry-forward is double the contracted. That gives you 4 units in month 3, but similarly you can eat into month 4 so have 6 units available.
The other way round, if in month 1 you used 2.6 units you have eaten into month 2's, so in month 2 you only have 1.4 of contracted, plus the possibility of eating into month 3 as above.
However! That last case means in month 2 you can actually use 3.4 units with no problem. But if you use 3.7 units, then you are trying to carry forward (into month 3) an overusage of 2.3 units. You can't do that as you only contracted for 2 units, so the 0.3 has to be covered by a purchase of another unit at £5.99. Leaving you with 0.7 available in month 3.
Or of course, as I understand it, you could have upgraded in month 2 to get 3GB from the start of month 3 onwards at the standard price and have the 0.7 units available that way.
Plus of course you can eat into month 4 to increase the 0.7.
Do you like my mud-bath?
Edit - Note the rates change at the start of April. Second edit - The new rates.
Bob's broadband basic info/help site:
www.robertos.me.uk
ISP history: Demon dialup >> Freeserve dialup >> BT Broadband >> Prodigynet >> Newnet >> O2 Standard.
Purple Cloud for
domain,
email and
web space.
Edited by RobertoS (Tue 09-Feb-10 12:47:35)