Solar System & Battery Sizing for 4,000 kWh/Month in Washington, USA
Complete photovoltaic engineering breakdown for a 4,000 kWh/month (133.3 kWh/day) electricity profile in Washington, USA (3.8 Peak Sun Hours/day).
Technical Specification Table — 4,000 kWh/Month Solar System (Washington, USA)
| Monthly / Daily Electricity Consumption | 4,000 kWh/month (133.3 kWh/day) |
| Location Peak Sun Hours (PSH) | 3.8 hours/day (Washington, USA) |
| Required PV System Size (80% Performance Ratio) | 44.0 kWp DC |
| Number of Solar Panels (440W N-Type Bifacial) | 100 panels |
| Roof Area Required | 205.0 m² (2,207 sq ft) |
| Recommended Hybrid Inverter Rating | 39.3 kW AC |
| Recommended LiFePO4 Battery Storage (85% DoD) | 102.0 kWh Nominal (86.7 kWh Usable) |
| Estimated Annual Output | 48,822 kWh/year (~4,068 kWh/month) |
| Estimated System Turnkey Cost (Before Tax Credits) | $119,680 |
| Annual Electricity Bill Savings (@ $0.13/kWh) | $6,347/year ($529/month) |
Frequently Asked Questions
How many solar panels are needed for 4,000 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 4,000 kWh (133.3 kWh/day) requires a 44.0 kWp solar array, which equals 100 standard 440W N-Type solar panels occupying 205.0 m² (2207 sq ft) of roof space.
What size solar battery bank do I need for 4,000 kWh/month?
To cover evening and overnight loads (65% of daily consumption at 85% LiFePO4 depth of discharge), a 102.0 kWh nominal (86.7 kWh usable) LiFePO4 battery bank paired with a 39.3 kW hybrid inverter is recommended.
How much money will a 44.0 kW solar system save in Washington, USA?
Generating approximately 48,822 kWh per year at an average local tariff of $0.13/kWh, the system saves $6,347 per year ($529/month) with an estimated payback period of 18.9 years.