How Much Power Does A 4.5 kW Solar System Produce Per Day, Month, And Year? (2026)
A 4.5 kW DC solar system produces about 15–25 kWh per day depending on location — roughly 5,400–8,900 kWh per year. At U.S. average sun (4.98 PSH) with PVWatts v8 derate: 18.6 kWh/day, 566 kWh/month, 6,790 kWh/year. That covers about 65 % of the average American home. 4.5 kW is a good fit for small households, partial-offset systems, or homes with gas heat — but if your roof has room for one more panel, stepping up to 5 kW is almost always worth it.
I built a 6 kW array on my own house in 2024 — 14 panels. A 4.5 kW system is 11 panels, about 78 % of my install. At my location it would cover most of my household consumption but wouldn't leave headroom for an EV or heat pump. That is the practical limit of a 4.5 kW system: it does the job today, but it doesn't future-proof.
The Formula
kWh/day = 4.5 kW × PSH × 0.83
The 0.83 derate is the PVWatts v8 combined DC system loss (14 %) plus inverter efficiency (~96 %). The older version of this article used no derate at all — every number was 17 % too high. See How To Calculate Solar Panel Output for the full derate breakdown.
4.5 kW System Output In 12 U.S. Cities
| City | PSH | kWh/day | kWh/month | kWh/year | % of avg home | Annual savings @ state rate |
|---|---|---|---|---|---|---|
| Phoenix, AZ | 6.54 | 24.4 | 743 | 8,920 | 85 % | $1,249 ($0.14/kWh) |
| Las Vegas, NV | 6.41 | 23.9 | 728 | 8,740 | 83 % | $1,136 ($0.13/kWh) |
| Los Angeles, CA | 5.61 | 21.0 | 637 | 7,650 | 73 % | $2,295 ($0.30/kWh) |
| Denver, CO | 5.66 | 21.1 | 643 | 7,720 | 74 % | $1,081 ($0.14/kWh) |
| Austin, TX | 5.30 | 19.8 | 602 | 7,230 | 69 % | $1,012 ($0.14/kWh) |
| Miami, FL | 5.48 | 20.5 | 623 | 7,480 | 71 % | $972 ($0.13/kWh) |
| Atlanta, GA | 5.04 | 18.8 | 573 | 6,870 | 65 % | $893 ($0.13/kWh) |
| Boston, MA | 4.70 | 17.6 | 534 | 6,410 | 61 % | $1,795 ($0.28/kWh) |
| Chicago, IL | 4.27 | 15.9 | 485 | 5,830 | 56 % | $933 ($0.16/kWh) |
| Seattle, WA | 3.95 | 14.8 | 449 | 5,390 | 51 % | $593 ($0.11/kWh) |
| Anchorage, AK | 3.17 | 11.8 | 360 | 4,320 | 41 % | $994 ($0.23/kWh) |
A 4.5 kW system never fully offsets the average U.S. home in any location. It comes closest in Phoenix (85 %) and falls to 41 % in Anchorage. For full offset, size up to 6.5–7 kW.
Who Should Size For 4.5 kW?
| Scenario | Why 4.5 kW works |
|---|---|
| Small apartment / condo | Consumption 4,000–6,000 kWh/year, small roof section |
| Home with gas heat + gas water heater | Electric bill is 5,000–7,000 kWh/year after gas covers heating |
| Partial-offset budget system | Want to reduce the bill by 50–70 % without the upfront cost of full offset |
| Constrained roof area | Only ~230 sq ft of usable south-facing roof (11 panels) |
| Net-metering cap | Some utilities cap residential solar at 5 kW AC — a 4.5 kW DC system produces about 3.8 kW AC, well under cap |
4.5 kW vs 5 kW — The One-Panel Question
4.5 kW is 11 × 410 W = 4.51 kW. One more panel makes it 12 × 410 W = 4.92 kW — effectively 5 kW.
| 4.5 kW (11 panels) | 5 kW (12 panels) | |
|---|---|---|
| Annual kWh (avg sun) | 6,790 | 7,560 |
| Extra kWh | — | +770 |
| Extra annual savings @ $0.165/kWh | — | +$127 |
| Marginal panel + install cost | — | ~$400 |
| Payback of that one panel | — | 3.1 years |
That extra panel pays for itself in about 3 years. Unless your roof physically cannot fit 12 panels, always go 5 kW over 4.5 kW.
2026 Cost And Payback
| Cost item | 4.5 kW system |
|---|---|
| Installed cost ($3.10/W) | $13,950 |
| Federal credit (2026) | $0 |
| Net cost | $13,950 |
| Location | Annual savings | Payback |
|---|---|---|
| Hawaii ($0.42/kWh) | $2,633 | 5.3 yr |
| California ($0.30/kWh) | $2,295 | 6.1 yr |
| Massachusetts ($0.28/kWh) | $1,795 | 7.8 yr |
| U.S. average ($0.165/kWh) | $1,120 | 12.5 yr |
| Washington ($0.11/kWh) | $593 | 23.5 yr |
Common Misreadings
- "4.5 × 5 PSH = 22.5 kWh/day." Missing the 0.83 derate. The correct number is 4.5 × 5 × 0.83 = 18.7 kWh/day.
- "4.5 kW covers my home." Only if your home uses under ~7,000 kWh/year and you're in a sunny location. The U.S. average home needs 6.5–7 kW for full offset.
- "I should get 4.5 kW to save money." The difference between 4.5 kW and 5 kW is one panel (~$400). That extra panel pays back in 3 years and produces electricity for 25. Saving $400 upfront costs $3,000+ over the system lifetime.
Bottom Line
A 4.5 kW system — 11 modern 410 W panels — produces about 18.6 kWh/day and 6,790 kWh/year at U.S. average sun. It covers 50–85 % of a typical home and is best suited for small households, partial-offset budgets, or constrained roof areas. For most homeowners, spending ~$400 more for a 12th panel and stepping up to 5 kW is a trivially easy decision.
Tap to see sensitivity analysisSensitivity analysis
| Scenario | Value |
|---|---|
| Low (-20%) | 7,767 kWh |
| Expected | 9,709 kWh |
| High (+20%) | 11,651 kWh |
A 10% increase in peak sun hours adds 971 kWh per year. PSH varies by season — winter values may be 30% lower than the annual average.