Metal-halide perovskites have emerged as a promising class of next-generation solar cells. Here, we assess what lifetimes and efficiencies perovskite solar cells (PSCs) have to reach to lower the price of commercial residential photovoltaics (PVs) further. We find that using light and flexible substrates, as opposed to heavy and rigid ones, reduces the total installed system cost of PSCs, culminating in a lower balance of system (BOS) cost, as it is possible to use different mounting methods. Concretely, we analyze the scenario when the modules are directly placed onto a roof without requiring a racking system. This reduces both labor and material costs. Furthermore, it effectively lowers the necessary efficiency or lifetime of PSCs (T80 value) to achieve the same electricity cost as commercialized silicon. For 2021, we find that a rigid perovskite module with 17% efficiency would need at least 24 years to become competitive with residential-installed silicon. In comparison, a light, flexible module with the same efficiency would only need to last 19 years. In 2030, with the accordingly projected BOS costs, a 23% efficient perovskite module would need to last 24 years if rigid but only 17 years if flexible. Finally, we extend our analysis toward tandem structures with perovskite-silicon or all-perovskite tandem architectures. We find that flexible PSCs present a promising commercialization route because it can enable low manufacturing and BOS deployment costs, which opens up commercial viability at lower efficiencies or lifetimes. Metal-halide perovskites have emerged as a promising class of next-generation solar cells. Here, we assess what lifetimes and efficiencies perovskite solar cells (PSCs) have to reach to lower the price of commercial residential photovoltaics (PVs) further. We find that using light and flexible substrates, as opposed to heavy and rigid ones, reduces the total installed system cost of PSCs, culminating in a lower balance of system (BOS) cost, as it is possible to use different mounting methods. Concretely, we analyze the scenario when the modules are directly placed onto a roof without requiring a racking system. This reduces both labor and material costs. Furthermore, it effectively lowers the necessary efficiency or lifetime of PSCs (T80 value) to achieve the same electricity cost as commercialized silicon. For 2021, we find that a rigid perovskite module with 17% efficiency would need at least 24 years to become competitive with residential-installed silicon. In comparison, a light, flexible module with the same efficiency would only need to last 19 years. In 2030, with the accordingly projected BOS costs, a 23% efficient perovskite module would need to last 24 years if rigid but only 17 years if flexible. Finally, we extend our analysis toward tandem structures with perovskite-silicon or all-perovskite tandem architectures. We find that flexible PSCs present a promising commercialization route because it can enable low manufacturing and BOS deployment costs, which opens up commercial viability at lower efficiencies or lifetimes.