User Manual

1.5 Outline of max demand measurement concept KEW6310
1.7 KEW6310
1.5 Outline of max demand measurement concept
In some coun tries, la rge co nsu mers of ele ctri ci ty w ill usua lly have a max imu m deman d con tra ct w ith th e pow er
company. Su ch co nt ract va ries from country to coun try . The following is an explana tion of a ty pical Japane se
maximum demand contract.
● Maxi mum De mand co n tra ct
In such a contract the electricity tariff rates (i.e. for kWhr units) are based upon the consumer’s maximum
power demand. The maximum demand is the maximum of average powers recorded over a 30min intervals.
This is measur ed by the maxi mum de mand me ter belo ngin g to the pow er co mpany . Le t’s assu me th a t a pow er
company ha s the fo ll ow ing appli cabl e rate s.
$2 per KWhr unit for a recorded max demand 300KW during a year
$4 per KWhr unit for a recorded max demand 500KW during a year
$5 per KWhr unit for a recorded max demand 600KW during a year
Assuming that the consumer is on the 500kW/year rate (ie. $4), and the recorded max demand during a
particular day (say 15th Janu ary ) is 600kW . Then the new applicable rate from 1st February onwards will be the
600kW/year ra te (ie. $5 ) for th e next 36 5 days. If a y ear late r, on Feb ruary 1st the recorde d max imu m demand
is 300kW, then the new appl icable rate s w ill be ch ang ed to 300kW/y ea r rate (i.e . $2) for the subseq uen t 365
days. However i f during this pe riod, the max demand goes up again , and say 600kW i s recorded on 15 th March ,
the applicable rates change again to the 600kW/year rate (i.e.$5) for the subsequent 365 days.
● Benefits of maximum demand control
It is thus important for consumers with such contracts to monitor closely flu ctuation s in their pow er demand to
ensure that their max demand limits are not exceeded and thus incur higher tariffs. Maximum Demand control is
more effec ti ve i n countries w ith higher electricity tariffs.
● Status of maximum demand contract
In the past, in Japan, only consumers whose electricity supply was rated at 600kW or more used to enter into a
demand con tra ct. How ever, no w adays power companies in stall maxi mum d emand me ters a t all co n sumers
whose supply is rated 70kW or more.
● Maximum Demand measurement limitations
N.B. The readi ngs fro m pow er co mp any max imu m dema nd mete r and fro m the 630 0 w ill no t ma tch compl etely
due to an obvious time-lag difference in the start of the integration period (eg.30mins) over which the max
demand is taken.