PG&E; said its earnings will plunge by nearly half.

Complaining of delays by the California Public Utilities Commission in deciding how much of its investment in the Diablo Canyon nuclear plant it can recover from customers, Pacific Gas & Electric said it will make accounting changes that will slash 1987 net income by about $470 million, or $1.25 per share. The utility said its cash flow is unchanged and its dividend will be maintained. San Francisco-based PG&E; has been charging customers 40% of its cost of running Diablo Canyon, but its books show that it has been recovering the full cost of $1.3 billion a year, a common utility practice while rate approval is pending. During the unusually long delay, the uncollected portion has grown to $1 billion and PG&E; said it is “prudent” to erase these accounts receivable.