The global wind and solar PV industry has transitioned from a subsidy-dependent niche market to a commercially viable sector that is dominating global capacity expansions. However, integrating these renewable energy resources, with their variable nature, onto the electricity grid poses new challenges for system operations. This thesis explores variable renewable energy (VRE) integration, through multiple scales of energy modelling and analysis from the integrated assessment model MESSAGE, to the country-scale electricity system model LEAP, and the production cost model introduced in this work entitled SILVER. The MESSAGE and LEAP models have large-scale, long-term representations of the energy system that enable analysis of alternative energy policies, cross-sector environmental impacts, and overarching cost trends, but do not have the spatial-temporal resolution to represent site-specific, variable VRE generation profiles. Thus, SILVER, for the Strategic Integration of Large-capacity Variable Energy Resources, is designed as a highly flexible production cost dispatch tool. Technologically, SILVER represents the full gamut of grid balancing strategies:​ building flexible and dispatchable generation assets, interconnecting geographically dispersed resources and VRE types, shifting flexible loads through demand response, shifting generation profiles through storage technologies, curtailing excess generation, interconnecting the electricity sector with the transport sector, and improving VRE forecasting methodologies. SILVER relies on hourly wind and solar generation time-series data, produced by the newly developed GRETA (Global Renewable Energy Atlas Time) tool, which has been launched as an open access web-portal. SILVER is applied to three VRE integration applications:​ moving towards a fully-renewable Ontario electricity system including 87% VRE penetration, demand response, electric vehicles, storage assets, and an expanded transmission network;​ quantifying storage asset commercial viability in electricity systems with different flexibility factors, VRE penetrations, and financial remuneration mechanisms;​ and exploring the role of decentralized generation and electric vehicles at a city-scale in a developing country context. The results demonstrate the highly system-specific nature of VRE integration, with the VRE resource typology, the non-VRE system flexibly, VRE penetration, and degree of VRE centralization having significant impacts. The interdependence between these electricity system factors in terms of curtailment rates, GHG emissions, electricity system costs, and flexibility requirements recommends an integrated planning approach.