Owners of leaky, drafty commercial and apartment buildings might soon be able to get energy-saving tips from the very people who have sent them skyrocketing energy bills in recent years.

Under the federal Commercial and Apartment Conservation Service (CACS) program, building owners will be able to request energy audits from local electric and natural gas utilities.

Owners qualify if their apartments contain more than four units or if their commercial properties have average monthly consumption rates of less than 4,000 kilowatt-hours or 1,000 therms of gas or its oil equivalent.

These audits will spell out which conservation and solar measures can be taken to retrofit their buildings; what the resulting energy savings are likely to be, and a list of suppliers, contractors and lenders who can help. CACS, established by the Department of Energy, is required under the National Energy Conservation Policy Act.

Late last month, DOE proposed regulations for state energy offices to establish CACS programs for their utilities, along some of the same lines in use for residential audits on buildings with one to four units.

The CACS audits, however, will be somewhat less complex. Where the Residential Conservation Service (RCS) rules require detailed costs and savings estimates tailored to each audited home, the CACS rules call for an inspection to determine simply whether there is a need for any of the measures.

In the new CACS proposal, DOE says it seeks to provide greater flexibility for the states to set up their programs. Utilities are to perform on-site inspection of commercial and apartment buildings, upon request from eligible customers.

The inspection must address three areas: 1) the rate and quantity of energy consumption; 2) the operation and maintenance procedures appropriate to the building, and 3) the need, if any, for the purchase and installation of program measures.

This does not mean that the utility auditor must conduct extensive, long-term research into the energy efficiency of the existing commercial and apartment building stock. Still, DOE says, utilities will need to develop information on "typical" building performance.

The conservation and solar energy retrofit options that will have to be included in CACS audits range from the obvious and inexpensive, such as caulking and ceiling insulation, to the commonplace and more costly, such as air conditioner and oil burner replacement.

Thereare also the less obvious but sensible options, such as replacement or modification of lighting systems. (Lighting can consume over 20 percent of the total energy required by modern office buildings, according to DOE's Solar Energy Research Institute.) The rules also spell out the types of solar energy systems that are to be included in the audits, such as passive solar space heating and cooling systems.

In picking the list of eligible retrofit options, DOE relied on computer calculations of how quickly the changes would pay for themselves through energy savings. As with the RCS, a CACS retrofit measure must be included in an audit only if it would pay back the investment within seven years.

If a measure does not offer such a return, it does not have to be included in an audit, although an individual state can order utility auditors to include it. Among the measures that failed DOE's pay-back test are active solar space heating systems, combined active solar space heating and solar hot water systems, windmills and cogeneration systems that generate electricity as well as provide heating.

While these audits may sound expensive, a utility's charge to customers is limited to $15 per unit or actual cost, whichever is less. DOE's sampling of existing utility audit programs for commercial and apartment buildings -- a study DOE concedes is unscientific -- shows that the audits can cost $118 to $600, depending on the complexity of inspection.

RCS audits, by contrast, cost a utility about $150 and no more than $15 per customer, says Washington Gas Light spokesman Paul Young. DOE points out that the majority of utilities in its sample either did not charge their customers anything or kept the price tag under $25.

Potomac Electric Power Co. and WGL already offer audits for commercial, apartment and residential buildings. Some modifications are likely to be needed to bring these audits into compliance with the rules to be drawn up by the District and Maryland, as with the RCS regulations. The District expects final approval from DOE on its RCS program within 30 to 45 days. Maryland's RCS program is in effect now. State CACS rules in these jurisdictions will be developed as the regulations become final.

As permitted under DOE rules, Virginia never prepared an RCS program and will now fall under the so-called federal stand-by plan also proposed late last month by DOE. A standby plan for CACS, required by law to handle those states without DOE approved plans of their own, will be drafted by the Energy Department in the coming months.

Local utilities were unsure immediately how the new rules would affect them, since the companies have not yet had time to review them thoroughly. However, Joe Van den Berg, manager for energy utilization technology at the electric utility trade group Edison Electric Institute, calls them a "step in the right direction."

He said they were "consistent with President Reagan's concepts of regulatory reform" in lessening the burden on the power companies. It remains uncertain whether utilities will have to hire additional personnel to conduct the CACS audits, Van den Berg said, because RCS auditors can handle the added audits "only in certain situations." One change he favors would limit eligible customers to building owners whose tenants are individually metered. In master-metered buildings, he noted, it is hard to tell how much energy any one tenant is using.