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The increasing share of intermittent and non-dispatchable power sources, such as wind and solar photovoltaic (PV) power in the electrical energy mix, poses challenges to power system stabil-ity. One possible way to dampen fluctuations during frequency instability situations or remove bottlenecks across the power system is to install battery energy storage systems (BESSs) or to enable demand side management via electric vehicle (EV) batteries. The BESS can operate in the power system transmission or distribution or behind-the-meter (BTM), mitigating power system challenges and electricity market inefficiencies. Although BTM BESS or aggregating EVs fleets can operate similarly to utility-scale BESS systems, a significant common challenge is to determine the specific services these systems should provide to maximize their profits. This thesis investigates the techno-economics of operating these technologies in different con-texts: 1) economics of participation on spot and ancillary services markets for utility-scale solar PV power plant for a case-study in Sweden, 2) the most profitable markets and sizes of BESS combined with utility-scale solar PV power plants using techno-economic analysis frameworks applied in Swedish and German contexts, 3) techno-economics of adding peak shaving (PS) and participation on local flexibility markets if using, BTM BESS for a Swedish church pow-ered with PV system, and 4) techno-economics of minimizing monthly cost of electricity for residential buildings with both rooftop PV system and EV smart charging. The input data for all four studies are historical market prices and measured frequency, PV power, and electricity consumption data. For case study 1), operation on ancillary service markets increases the profits by 20% compared to only participating on the spot market for a utility-scale PV power plant in Sweden. For case study 2), adding a utility-scale BESS to an existing PV park does not result in a lower payback period than if implementing a stand-alone BESS. However, the payback period differs between Sweden and Germany, being 1.8 and 6.8 years, respectively, using the market prices from 2023. This is explained by the lower frequency market prices for Germany compared to Sweden. For case study 3), the BTM BESS results do not show high profitability for adding the operation on the local energy market or performing PS in a church case study. Lastly, for case study 4), EV smart charging was shown to lower the yearly electricity cost by up to 15% on average for residential buildings powered by rooftop PV systems for the year 2021. This gain is higher when power-based networks are applied instead of the energy-based network tariffs relative to the immediate charging scenario. In conclusion, the thesis shows that the economic results demonstrate profitability for BESS, utility scale PV, and EVs smart charging in Sweden while alleviating some of the power system challenges. For future work, investigating the integration of forecasting methods with market models to optimize PV power usage with EVs smart charging would be interested to enhancing short-term trading strategies and ASMs participation.