Start with Usage
System sizing starts with annual kilowatt-hours, not roof area or budget. Divide annual usage by your region's production factor and you have the honest baseline — for most homes, a kilowatt of panels yields between eleven and fifteen hundred kilowatt-hours a year.
The Offset Target
Full offset maximizes independence, but where export rates are poor, the last panels earn the least. Many homes land best between eighty and one hundred percent — big enough to erase most of the bill, small enough that every panel pays its way.
Roof Constraints
Setback rules, vents, chimneys, and shade zones all subtract usable area. When ideal size exceeds usable roof, higher-efficiency panels close the gap — at a premium worth paying only when the space genuinely runs out. Design is the art of fitting the math onto the shingles.
Room to Grow
An EV adds three to four thousand kilowatt-hours a year; a heat pump can add more. If either is on your horizon, size for it now or ensure the inverter and panel layout leave clean expansion room. Retrofitting capacity costs more than planning it.
Oversizing wastes money on day one. Undersizing wastes it for twenty-five years.
Samuel Kim
SOLWELL ENERGY ADVISOR
