Solar System & Battery Sizing for 1,150 kWh/Month in Washington, USA
Complete photovoltaic engineering breakdown for a 1,150 kWh/month (38.3 kWh/day) electricity profile in Washington, USA (3.8 Peak Sun Hours/day).
Technical Specification Table — 1,150 kWh/Month Solar System (Washington, USA)
| Monthly / Daily Electricity Consumption | 1,150 kWh/month (38.3 kWh/day) |
| Location Peak Sun Hours (PSH) | 3.8 hours/day (Washington, USA) |
| Required PV System Size (80% Performance Ratio) | 12.76 kWp DC |
| Number of Solar Panels (440W N-Type Bifacial) | 29 panels |
| Roof Area Required | 59.4 m² (639 sq ft) |
| Recommended Hybrid Inverter Rating | 11.4 kW AC |
| Recommended LiFePO4 Battery Storage (85% DoD) | 29.3 kWh Nominal (24.9 kWh Usable) |
| Estimated Annual Output | 14,158 kWh/year (~1,180 kWh/month) |
| Estimated System Turnkey Cost (Before Tax Credits) | $34,707 |
| Annual Electricity Bill Savings (@ $0.13/kWh) | $1,841/year ($153/month) |
Frequently Asked Questions
How many solar panels are needed for 1,150 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 1,150 kWh (38.3 kWh/day) requires a 12.76 kWp solar array, which equals 29 standard 440W N-Type solar panels occupying 59.4 m² (639 sq ft) of roof space.
What size solar battery bank do I need for 1,150 kWh/month?
To cover evening and overnight loads (65% of daily consumption at 85% LiFePO4 depth of discharge), a 29.3 kWh nominal (24.9 kWh usable) LiFePO4 battery bank paired with a 11.4 kW hybrid inverter is recommended.
How much money will a 12.76 kW solar system save in Washington, USA?
Generating approximately 14,158 kWh per year at an average local tariff of $0.13/kWh, the system saves $1,841 per year ($153/month) with an estimated payback period of 18.9 years.