Solar System & Battery Sizing for 625 kWh/Month in Illinois, USA
Complete photovoltaic engineering breakdown for a 625 kWh/month (20.8 kWh/day) electricity profile in Illinois, USA (4.4 Peak Sun Hours/day).
Technical Specification Table — 625 kWh/Month Solar System (Illinois, USA)
| Monthly / Daily Electricity Consumption | 625 kWh/month (20.8 kWh/day) |
| Location Peak Sun Hours (PSH) | 4.4 hours/day (Illinois, USA) |
| Required PV System Size (80% Performance Ratio) | 6.16 kWp DC |
| Number of Solar Panels (440W N-Type Bifacial) | 14 panels |
| Roof Area Required | 28.7 m² (309 sq ft) |
| Recommended Hybrid Inverter Rating | 5.5 kW AC |
| Recommended LiFePO4 Battery Storage (85% DoD) | 15.9 kWh Nominal (13.5 kWh Usable) |
| Estimated Annual Output | 7,914 kWh/year (~660 kWh/month) |
| Estimated System Turnkey Cost (Before Tax Credits) | $16,632 |
| Annual Electricity Bill Savings (@ $0.17/kWh) | $1,339/year ($112/month) |
Frequently Asked Questions
How many solar panels are needed for 625 kWh per month in Illinois, USA?
With an average of 4.4 Peak Sun Hours per day in Illinois, USA and an 80% system performance ratio, a monthly usage of 625 kWh (20.8 kWh/day) requires a 6.16 kWp solar array, which equals 14 standard 440W N-Type solar panels occupying 28.7 m² (309 sq ft) of roof space.
What size solar battery bank do I need for 625 kWh/month?
To cover evening and overnight loads (65% of daily consumption at 85% LiFePO4 depth of discharge), a 15.9 kWh nominal (13.5 kWh usable) LiFePO4 battery bank paired with a 5.5 kW hybrid inverter is recommended.
How much money will a 6.16 kW solar system save in Illinois, USA?
Generating approximately 7,914 kWh per year at an average local tariff of $0.17/kWh, the system saves $1,339 per year ($112/month) with an estimated payback period of 12.4 years.