Electricity pricing Tariffs

Tariffs Definition: Different methods for charging consumers, Rate of payment for consumption of electricity

Some basis Purely on Total energy (kwh) consumption Maximum demand and total energy consumption Amount of energy consumed Power factor of the load Time at which the load is required Type of the customer ( Industrial , commercial or residential ) HT (High voltage) & LT customers

Some basis Purely on Total energy (kwh) consumption Flat rate tariff Maximum demand and total energy consumption Two part Tariffs Amount of energy consumed Block rate Tariff Power factor of the load Power factor Tariff Time at which the load is required Time of the Day Tariff

Some basis Type of the customer ( Industrial , commercial or residential ) HT (High voltage) & LT customers

Industrial consumers Basis of charging Industrial consumers is generally Two part tariffs; One part of charge is proportional to the maximum demand ( kilowatts) because this affects the size of the plant to be installed and corresponding fixed charges on capital. The second part of charge is proportional to the energy consumed (killowatt-hours) monthly or annually.

Residential consumers in Early days In early days policy was to induce customers to use more energy, some companies used two or more flat rates First few kwh are charged at certain rate, the next few at a lower rate, next few at a still lower rate and so on.

Residential consumers Now a days Due shortage of generation Now a days policy is to discourage customers to use more energy, some companies use two or more flat rates First few kwh are charged at certain rate, the next few at a higher rate, next few at a still higher rate and so on.

Incentives and penalty Consumers taking off peak power Special cheap rates to help to improve the load factor of the system. Consumers whose pf falls below a specified limit may be charged more; have a penalty clause in the rate structure. Alternatively the consumers may be charged on combined killovolt-ampere-hour ( kVA) and killowatt-hour (kwh)basis.

Modern techniques Electricity Regulatory commission ( ERC) governs the fixation of tariffs for various Consumers. The rate structure should be arranged so as to help the system to have better load factor and power factor so that electrical energy can be produced and sold more cheaply.

Energy supplied to consumers kwh generated kwh used by station auxiliaries Kwh loss in transmission kwh Received Energy to consumer = kwh generated – kwh used by aux – kwh loss in transmission

Some Examples 2.9 (mvd) Apower station has a installed capacity of 20000 kw , the cost of the station is rs 1200, per kw . The fixed costs are 13% of the cost of investment. On full load at 100% load factor, the variable cost of the sttio per year are 1.5 times the fixed costs.Assume that there is no reserve capacity of the plant and that the variable cost are proportional to to the energy production Find the cost of generation per kwh at load factors of 100% 80%, 60%, 40% and 20% and plot the curve. (ans Load fctors and cost per kwh; 100% 4.46p ,; 80% 5.65p; 40% 7.15p; 20% 11.5p)

Some Examples 2.10 (mvd) Apower station has a installed capacity of 20000 kw , the cost of the station is rs 1200, per kw . The fixed costs are 13% of the cost of investment. On full load at 100% load factor, the variable cost of the sttio per year are 1.5 times the fixed costs.Assume that there is no reserve capacity of the plant and that the variable cost are proportional to to the energy production Find the cost of generation per kwh at load factors of 100% 80%, 60%, 40% and 20% and plot the curve. (ans Load fctors and cost per kwh; 100% 4.46p ,; 80% 5.65p; 40% 7.15p; 20% 11.5p) Tis station supplies load to consumers. The cost of distribution system increases the fixed cost by 75% { this includes payment of dividend to stock holders} and the variable cost on full load at 100% load factor( at the station) by 20% Work out the two part tariff per killowatt per month and per kwh consumed. When a) the load factor is 80% and (i) the diversity factor among the consumer is 2.3 and (ii) the diversity factor among the consumer is 1.75 b) the load factor is 60% and (i) the diversity factor among the consumer is 2.3 and (ii) the diversity factor among the consumer is 1.75 The losses in the distribution system may be taken as 10% ( Ans: (a) (i) Rs 9.75per kw per month and Rs 3.59 per kwh;(ii) Rs 12.8per kw per month and Rs 3.59 per kwh (b) (i) Rs 9.75per kw per month and Rs 3.59 per kwh;(ii) Rs 12.8per kw per month and Rs 3.59 per kwh