Shaded 1957 ranch, microinverter retrofit

The problem

Two mature willow oaks on the south property line put the main roof plane at a total solar resource fraction of 71 percent between November and February. A previous contractor had quoted a string system across both planes, which would have let the shaded modules pull down the unshaded ones every winter afternoon.

The service panel was an original 100 A board with no spare spaces and a bus rating that ruled out a back fed breaker of the size required.

What we did

Microinverter per module so each panel produces independently. A shaded module at 40 percent output no longer costs its neighbours anything.

Split the array across the south and west planes rather than forcing everything onto the shaded south face, which raised the late afternoon yield in summer.

Replaced the 100 A panel with a 200 A service and moved the meter base at the same time, which was going to be needed within a decade regardless.

What happened

Measured first year production came in at 8,410 kWh against a modelled 8,200 kWh, about 2.6 percent above model.

Per module telemetry showed exactly the winter afternoon dip predicted by the shade study, which gave the owner confidence that the model was honest rather than optimistic.

The new service left headroom for the Level 2 charger the household added the following spring.