1. UK rule-of-thumb (RoT) Peak Sun Hours (PSH): 3.5 summer, 2.0 spring/autumn, 1.0 winter
2. For calc use Peak Sun Hours (PSH) = 2 h for UK spring/autumn.
3. Assume a typical house uses 10 kWh/day, of which 6 kWh at the evening.

PV size = daily kWh ÷ PSH × 1.3 = 10 ÷ 2 × 1.3 = 6.5 kWp.

*1.3 PV factor

Battery nominal

Evening kWh ÷ Depth of Discharge DoD (0.85) × small losses (approx. 1.1)

= 6 × 1.1 ÷ 0.85 = 7.8 kWh = rounded up 8 kWh.

1. Battery: 8 kWh nominal gives enough usable energy to run an average evening
2. Battery usable capacity ≈ nominal × DoD = 8 kWh × 0.85 ≈ 6.8 kWh.
3. Inverter: A 5 kW hybrid inverter will handle daytime loads;

RoT panels Qty: 15–16 panels (420–440 W panels).

Export limits

UK DNO permissions (G98/G99) may cap inverter export (e.g., 3.68 kW single-phase). Meaning larger batteries or export-limiting inverters

Orientation

1. South‑facing array (typical UK pitch ~30–40°): generation rises quickly in the morning, peaks hard at solar noon, then drops. Watts concentrated in a few hours.
2. East/West split: half of the panels look east (morning), half west (afternoon). You get two lower humps with a dip at noon. Net effect: longer, flatter output across the day – better for self‑use.