This section shows the impact that Renewable Energies have on a large utility in Northern California. The following study has been developed in .
Utilities in different parts of the world will select different sets of technologies depending on patterns of local electric demand, access to natural gas, coal, or other resources, and the extent and mix of local renewable resources.
One virtue of renewables is the large number of technological choices, although such variety also frustrates attempts to make simple, universal statements about their worth. However, a number of basic principles can be illustrated by examining the economics of alternative combinations of technologies that might be installed in a region with good, but not remarkable, access to renewable resources in the period after 2000.
Northern California is a representative area because its wind and solar resources are close to world averages and its use of hydroelectric power approximates the world average of 20%. Investment alternatives for this utility were analysed using the following assumptions:
Ten different capital and electricity generating options were analysed. These were based on the fuel price assumptions of the IPCC renewables-intensive energy scenario together with the above assumptions.
Table 16 Investment options 
The average cost of meeting the annual electricity needs and the fraction of electricity generated by each energy source are shown in the Tables below.
Table 17: cost of electricity 
The average cost of electricity generated with conventional equipment was found to be 4.9 cents per kWh. Costs would be reduced to 4.6 cents per kWh using the best performing gas turbines and coal gasification systems that are now coming onto the market and to 4 cents per kWh using advanced fossil-fuel generating equipment (3.7 cents per kWh if low-cost hydroelectric capacity is also available).
Table 18: Percent of electricity generated by source 
The costs are the result of an hour-by-hour simulation of the utility that considered electricity demand, the variable output of intermittent renewable equipment, the load-levelling capabilities of hydroelectric facilities, and the dispatching of coal, natural gas, and biomass fuelled plants. The selection of coal, biomass, and natural gas-burning plants was done to minimise the cost of serving loads not covered by other equipment within the constrains specified.
The tables show that a large portion (30%) of electricity generation could come from intermittent sources without increasing the average cost of electricity, and that this utility could operate almost entirely on renewable sources of energy (Option 9). The CO2 emissions in this case would be 97% less than for the conventional case (Option1).
Another finding of this analysis is that, with one exception, all the renewable portfolios considered could meet the systems load at a cost lower than that for a system with typical new coal and gas equipment. Also, in many of the cases, from 90 to 95% of all electricity comes from renewables. The high-renewables cases generates only 3-4% CO2 as the advanced fossil system. Yet, these large reductions in CO2 emissions are achieved at costs between 0 to 1% per kWh higher than in the least costly case.
For comparison, the average electric price for consumers today is 6.3 cents per kWh (a delivered price that includes transmission, distribution, and management costs, as well as generation costs).
Although utility portfolios that involved intermittent for more than 10% of the electricity generated were somewhat more expensive than utilities portfolios that made maximum use of advanced, highly efficient fossil fuel generators, even for the 50% intermittents case, the renewable system cost only 1.5 cents per kWh more than the advanced fossil system.
The reduced costs arising from the buffering demand on a utility system with hydroelectric equipment are apparent for both conventional and renewable-intensive cases. But hydroelectric power is particularly attractive when used to buffer the large fluctuations of output that arise at high penetrations of intermittent renewables.
An important parameter characterising small-scale photovoltaic systems located at sites dispersed throughout the utility system is the credit these systems are due because of their value in reducing transmission and distribution costs and increasing system reliability. This so-called "distributed credit" can reduce the net cost of photovoltaic systems considerably.