System size, batteries, and EV charging — DIY and off-grid sizing from your real usage.
Nameplate wattage is a laboratory number. What a panel delivers on your roof is that figure reduced by orientation, tilt, temperature, wiring, and inverter losses — which is why systems sized off panel ratings alone tend to disappoint. These calculators size from consumption instead: your real kWh, or the bill that reflects it. From there you can work outward to panel count, tilt and azimuth, inverter and charge-controller capacity, and battery bank sizing at a usable depth of discharge rather than a theoretical one. The EV tools answer the questions that decide the purchase — what a charge costs at home, how long it takes, and how it compares to the fuel it replaces.