Harraton, Washington — 4.2 kWp solar + 5 kWh battery on 1970s semi

The Harraton property is a classic 1970s 3-bed semi — concrete tile roof, south-east aspect, no major shading from the rear garden trees. The owner approached us in November 2025 after a year of monitoring energy prices through the autumn–winter peaks. He wanted a system that would deliver real bill reduction (not just SEG revenue) and partial backup capability for the occasional power cut.

After the site survey we recommended a 10-panel 4.2 kWp array — large enough to comfortably cover daytime base load plus partial battery charging, but not so large that it dramatically increased export at a much lower tariff than the import rate. The SolarEdge hybrid platform was chosen specifically for the power-optimiser shading resilience (a chimney on the south flank casts ~30 minutes of morning shadow in summer) and for the Backup Interface that gives the customer whole-home EPS during grid outages.

The 5 kWh battery sizing was set to cover the typical 4-6 kWh evening demand (16:00-22:00) without leaving any unused capacity. We typically recommend battery sizing at ~75% of typical evening peak demand — oversized batteries spend much of their life partially full, which doesn't materially improve economics.

Install completed over 2 days in March 2026. Scaffolding day 1, panels + inverter + battery + commissioning day 2. SolarEdge mySolarEdge app handed over with full historical monitoring. Octopus Outgoing Fixed application submitted within 48 hours of install certificate issue — first SEG payment received late April.

After 6 months of operation the owner reports 64% reduction in net electricity bill (import minus SEG export) vs the same 6 months prior. Self-consumption rate of 78% — high for a residential setup, reflecting the well-matched solar-to-battery sizing and his disciplined use of the SolarEdge app to time washing-machine and dishwasher runs during peak solar hours.