Climate change poses critical challenges for Qatar’s energy-intensive residential building sector. This study evaluates the impact of projected climate warming on optimizing rooftop solar photovoltaics (PV) for villas. An integrated modelling approach is employed, combining building energy simulation, PV system optimization, and performance assessment under varying climate scenarios. A typical Qatari villa is modelled in DesignBuilder and simulated under the baseline (2002) conditions and the projected years 2016, 2050, and 2100, reflecting incremental warming. Results show the villa’s annual electricity consumption will grow 22% by 2100, with summer peaks escalating to 26% driven by surging cooling demands. Techno-economic optimization in HOMER Pro (version 3.10) verifies a grid-connected rooftop PV system as optimal in all years, with capacity expanding from 7.4 kW to 8.2 kW between 2002 and 2100 to meet rising air conditioning loads. However, as temperatures increase, PV’s energy contribution declines slightly from 18% to 16% due to climate change degrading solar yields. Nonetheless, the modelled PV system maintains strong financial viability, achieving 5–8 years of paybacks across scenarios. This analysis provides empirical evidence of distributed PV’s effectiveness for Qatar’s households amidst escalating cooling consumption. However, maintaining solar mitigation potential requires evolving PV sizing methodologies and incentives to account for declining panel productivity at the country’s peak temperatures exceeding 50 °C. Overall, this study’s integrated framework evaluates residential solar PV systems’ capabilities and appropriate policy evolution under projected climate impacts for the first time in Qatar. The modelling approach and conclusions can inform building codes and pro-solar policies to accelerate adoption for emissions reduction. With villas representing over 100,000 units in Qatar, widespread rooftop PV integration can meaningfully contribute to national sustainability targets if implementation barriers are addressed considering climate change effects.