Solar System & Battery Sizing for 10,500 kWh/Month in Washington, USA
Complete photovoltaic engineering breakdown for a 10,500 kWh/month (350.0 kWh/day) electricity profile in Washington, USA (3.8 Peak Sun Hours/day).
Technical Specification Table — 10,500 kWh/Month Solar System (Washington, USA)
| Monthly / Daily Electricity Consumption | 10,500 kWh/month (350.0 kWh/day) |
| Location Peak Sun Hours (PSH) | 3.8 hours/day (Washington, USA) |
| Required PV System Size (80% Performance Ratio) | 115.28 kWp DC |
| Number of Solar Panels (440W N-Type Bifacial) | 262 panels |
| Roof Area Required | 537.1 m² (5,781 sq ft) |
| Recommended Hybrid Inverter Rating | 102.9 kW AC |
| Recommended LiFePO4 Battery Storage (85% DoD) | 267.6 kWh Nominal (227.5 kWh Usable) |
| Estimated Annual Output | 127,915 kWh/year (~10,660 kWh/month) |
| Estimated System Turnkey Cost (Before Tax Credits) | $313,562 |
| Annual Electricity Bill Savings (@ $0.13/kWh) | $16,629/year ($1,386/month) |
Frequently Asked Questions
How many solar panels are needed for 10,500 kWh per month in Washington, USA?
With an average of 3.8 Peak Sun Hours per day in Washington, USA and an 80% system performance ratio, a monthly usage of 10,500 kWh (350.0 kWh/day) requires a 115.28 kWp solar array, which equals 262 standard 440W N-Type solar panels occupying 537.1 m² (5781 sq ft) of roof space.
What size solar battery bank do I need for 10,500 kWh/month?
To cover evening and overnight loads (65% of daily consumption at 85% LiFePO4 depth of discharge), a 267.6 kWh nominal (227.5 kWh usable) LiFePO4 battery bank paired with a 102.9 kW hybrid inverter is recommended.
How much money will a 115.28 kW solar system save in Washington, USA?
Generating approximately 127,915 kWh per year at an average local tariff of $0.13/kWh, the system saves $16,629 per year ($1,386/month) with an estimated payback period of 18.9 years.