This study presents a techno-economic comparison of national-scale solar deployment strategies across four contrasting electricity systems—Japan, India, Germany, and Saudi Arabia—using a synthetic yet literature-calibrated scenario set. A bottom-up levelized cost of electricity (LCOE) model is coupled with constraint modules for land availability, grid flexibility/curtailment, and battery energy storage system (BESS) sizing. Country profiles differ by irradiance (capacity factor [CF]), balance-of-system (BOS) cost structure, labor/financing assumptions, and grid absorption limits. Across a 2025–2035 planning window, baseline utility-scale photovoltaic (PV) (no storage) yields system LCOE medians of ~€58–72/MWh (Japan), €30–38/MWh (India), €48–60/MWh (Germany), and €24–32/MWh (Saudi Arabia). Introducing firm capacity targets via PV + BESS (4 h) raises median system LCOE by + 14%–22% (Saudi Arabia/India), +23%–31% (Germany), and + 32%–41% (Japan), with storage capex and round-trip efficiency (RTE) dominating sensitivity. Land constraints (modeled as site scarcity and BOS premiums) add + 6%–12% to LCOE in Japan at utility scale; grid constraints (annual curtailment caps) add + 5%–10% in Germany unless paired with flexible BESS dispatch or curtailment-aware oversizing. A joint optimization of PV sizing, storage hours, and curtailment policy minimizes system cost: the cost-optimal storage duration clusters around 2.5–3.5 h (Saudi Arabia/India) and 3.5–4.5 h (Germany/Japan). Results highlight three levers for planners: (i) prioritize storage cost learning and utilization (cycle throughput) over raw capacity; (ii) co-optimize siting and BOS to mitigate land premiums; and (iii) adopt curtailment-tolerant grid codes to unlock low-cost overbuild. The framework offers a transparent, transferable method for countries to stress-test solar build-outs under real-world constraints.