EV + Solar Load Planning
in Rhode Island

The D-20 rate plan is a dedicated Time-of-Use tariff for National Grid Rhode Island customers who own electric vehicles. It provides reduced electricity pricing during off-peak hours (typically overnight), which reduces the cost of grid charging when solar is not producing. When combined with solar self-consumption during the day, a D-20 household can minimize their per-mile charging cost significantly.

Rhode Island's compact geography and well-established net metering program mean interconnection timelines are typically shorter than most states — often 3–4 months from application to an energized system. This compares favorably to Massachusetts (4–6 months) and some other Northeast markets. NuWatt manages the interconnection application with National Grid RI as part of every project.

The calculator uses real state peak sun hours, current utility rate data, and manufacturer-standard vehicle efficiency figures. System derate factor is 0.80 (NREL standard for real-world losses). Estimates are within ±15% of a precise NuWatt design, which factors in your actual roof orientation, shading, and local utility interconnection rules. Use the calculator for planning; get a NuWatt quote for a binding design.

Yes — and it is often the most cost-effective approach. NuWatt coordinates solar system design, panel installation, EV charger wiring, and permit filing as a single project. Combining the work reduces labor costs, requires only one set of permits and utility paperwork, and lets us right-size the electrical panel upgrade to handle both loads simultaneously.