發電廠發電量較用電量多,電會去左邊?

In Hong Kong, extra electricity pumps water from a lower reserver to a higher reserver. It can energy into potential energy of water.
During peak usage, it generate power by electricity by hydropower.

2009-01-11 17:54:00 補充：
missed "store"

當中能量會部份散失.點樣散失左?相信閣下都應該聽過下(超導體),佢係一種係極低溫既情況下電阻值等於0,姐係可以令發電量等於用電量,當中既效率能夠達到100%.但係相信冇人會用呢d禁貴既野黎做一條禁長既電纜,佢頂多做到條電纜粗d,搵d電阻細d既金屬去做材料,盡量令電阻減至最低.但係都會有電阻架-所以發電廠發電量一定較用電量多,d電係運輸個陣散失不少啦.

Just imagine a generator performs like a battery. If a light bulb of, say 10 Watts is connected to the battery, the battery will provide a power of 10 Watts. If another identical light bulb is connected in parallel to the first one, the battery will provide a power of 20 Watts by doubling the output current.
If more and more light bulbs are connected in paralel to the original arrangement, the output current of the battery will increase to provide additional power for the bulbs.
Therefore, the total electric current delivered by a power station is, in fact, depends on the total load consumption. More current will be drawn from the power station for an increase of load in peak periods. Even if more generators are connected to the power transmission network, the total current delivered by the station will not be increased much in case there is not a change of load. Hence, the power station would not generate any 'spare electricity' at all.
Notice that the running of a generator doesn't indicate that it must delivering power. A generator could be running but gives no current if no load is connected to it. In that case, there is wastage of energy because of friction on the generator core and energy loss on transmission cables. This is the reason why surplus generators are disconnected from the grid (power transmission network) in periods when electricity demand is low.

你既問題我唔係幾理解
1。發電廠總發電量通常只能夠用到 45% ~ 50%，而後備發電機既總發電量通常能夠用到 75%，因爲當電發出來之後有一部份會漏掉，有一部份則因爲運輸時要將電壓升高及降低時既損失（鐡損及銅損），絕緣漏電，故障短路，漏磁等等種種因數，各廠商機器功率效應，甚至偷電活動，都會導致電流無從計算，所以就係損失。
2。現時輸送電流既網絡係將好多架發電機並聯起來同步發電，當晚上電力需求量減少時就會脫離一些正在並聯發電機並停掉以節省能源。