The paper is devoted to optimization of reserves and reliability level. The four approaches presented will need deeper scientific research. 1. The sum of reserves' costs and losses of consumers is minimized to the determination of optimal reserves. 2. Two-stage approach: 2. 1. The sum of reserves' costs and consumers' losses is minimized to the determination of optimal requirements for reliability, security and supply, 2.2. The sum of reserves' costs is minimized to the determination of optimal reserves subject to the optimal reliability requirements. 3. The sum of reserves' costs is minimized to the determination of optimal reserves subject to the given reliability requirements. 4. Optimization of reserves by the market conditions. The paper also presents the possibilities to utilize higher share of transmission capacity avoiding violation of thermal transmission limits in network elements.