# Cost-Benefit Analysis of Small-Scale Rooftop PV Systems: The Case of Dragotin, Croatia
## 1 Introduction
Despite the increase in own consumption and self-sufficiency, most papers claim that PV systems with batteries will not be profitable if battery prices do not fall significantly [8; 9; 10; 11; 12] with an increase in the price of electricity from the grid [13]. It should also be taken into account that the lifespan of battery systems is about 10 years, so it is necessary to change the battery system once or twice. According to the authors, taking into account both technological progress and rising electricity prices, battery systems will not be profitable before 2030 without government incentives. According to [PERSON] et al. [14], the cost-effectiveness analysis suggests that most of the savings potential comes from direct own consumption of PV, and therefore relates to the cost of electricity. The inclusion of a heat storage system and/or a battery system does not pay off when comparing savings and investment costs, at least at current prices. An additional impetus to the development of own consumption comes from the increasing production of electric vehicles and support for their charging, which will enable the application of V2G technology (vehicle-to-grid). In this sense, electric vehicles will enable the storage of part of the electricity produced by their own PV system. However, one should be careful here because the working population is at work at a time when the largest production of PV systems and cannot charge cars at that time but only on weekends. A zero-energy building (ZEB) is a concept that is applied in buildings with a balance between energy production and consumption and close to zero energy or even positive in a typical year. Photovoltaic technology can play a leading role in achieving the goal of ZEB because it is one of the best-positioned technologies for increasing the energy self-sufficiency of buildings. The integration of PV systems into the electrical grid, in general, increases the complexity of grid management [15]. The variability of solar energy concerning weather conditions (along with variability on the load side) makes it difficult to manage PV production and consumption and requires special procedures to balance the system. These difficulties can be alleviated by the simultaneous development of:  
* Energy storage system;
* Smart electrical grids with optimized energy and power management;
* Method of predicting renewable production and consumer consumption. However, the volatility of energy production and variability of the load can cause an unstable power supply and high peak load [16]. Moreover, the planned mass deployment of electric vehicles can lead to a significant increase in the peak load of electricity demand [17] but can also be considered valuable parts of a smart grid [18]. One solution is to align consumption with solar production, as consumption in the building sector is generally not synchronized with the production of the PV system. Energy storage in this sense can help a lot in solving these problems [19]. The timing of household appliances in smart homes can be applied depending on variations in electricity prices, as well as on consumer loads [20] or external conditions [21]. [PERSON] et al. [22] proposed a model that schedules the time operation of household appliances in a system with PV production. The authors apply dynamic programming to schedule the operation of household appliances and use game theory to sell excess energy produced. [PERSON] et al. [23] proposed a house energy management system in which they incorporated a genetic algorithm, a cuckoo search algorithm, and crow search algorithms. [PERSON] et al. [24] propose a home energy management system, which implements a load transfer strategy and coordinates the timing of household appliances. This paper analyzes the cost-effectiveness of using a roof grid-connected PV system without battery storage in the rural continental part of Croatia on an existing family house in Dragotin, Croatia.