After two years of hearings and studies, a Maryland Public Service Commission hearing examiner has recommended that consumer-group-backed changes in the way electricity rates are calculated should be studied further or rejected outright.

The proposed order, which will be issued formally Friday and become effective April 18 unless appealed, will require the four Maryland producers of electricity to conduct sample tests, studies, and reviews of a number of proposed changes, as well as prepare a report on the advisability of offering discounts in certain instances.

Specifically, the examiner, Wilson B. Stringer, concluded that:

A plan under which poorer customers would be guaranteed a subsistence level of electricity regardless of their ability to pay must be considered by the state legislature rather than the commission.

"Marginal costing>" whereby a customer pays precisely what it costs to generate another kilowatt of electricity to replace the one he used, has not yet been studied enough.

Large users of electricity should continue to be allowed to buy electricity at lower rates than smaller users such as homeowners.

Until the completion of national studies now under way on the practicality of offering discounts to users of electricity during off-peak hours, no changes should be made in existing rate structures.

Many of those proposed changes had been opposed in general by the four Maryland utilities, Baltimore Gas and Electric Co. (BG&E), Delmarva Power & Light Co., Potomac Edison Co., and Potomac Electric Powe Co. (Repco).

The hearing examiner recommended a "cautious approach to rate reform" and said "extensive change (should be) made only on conclusive evidence from the national study or other reliable sources, including experimentation in Maryland."

Michael Darr Barnes, Montgomery County member of the three-member Public Service Commission, of which Stringer is an employee, said that any one of the parties to the case - as well as the PSC itself - can call for a review of the recommendations within the next 30 days.

The case that resulted in Stringer's proposed order was instituted by the PSC itself, which asked for an "investigation" to see if any changes should be made "to encourage conservation of electricity."

Gov. Marivn Mandel and the General Assembly also asked for a report on electricity rates from the PSC. Stringer's proposed order constitutes the bulk of that report, Commissioner Barnes said.

Stringer recommended that Maryland's four generating utilities each conduct an "experimental sample testing of about 200 large residential customers (apartment houses)" to determine how much electricity is used at specific times of the day.

In addition, Stringer also proposed that the utilities study the "practicality" of increasing charges to big users of air conditioning, such as apartments and shopping centers, conduct a review of existing differentials in rates based on season use, and prepare a report on discounts for large commerical and industrial users who switich their peak use to off-peak hours.

Stringer said of the marginal cost proposal that "there is too much uncertainty, instability, and a lack of knowledge" to adopt the plan now.

Allowing the poor to receive subsistence levels of free electricity is "properly a subject for consideration by the legislature" because of the "social aspects" involved, he said.