There are a large variety of quantum key distribution (QKD) protocols, which can provide unconditional security even with practically possible coherent states instead singlephoton ones. Most of them require equal intensities of  states emitted, which can be achieved only with some precision. However, in some state preparation schemes, for example, in those based on optical injection, equal intensities cannot be achieved without additional elements, which  increases the cost and complexity of QKD setup. In this work we analyze the influence of different state intensities on achievable secret key rate in classical BB84 scheme.