SAVE
$0+
Over 25 Years
Most homeowners need:
25-year cost comparison for a $300/month US electric bill.
Without solar
25-year utility cost
$175,000
Rates rise ~3% per year (EIA avg.)
With solar
Net system cost
$45,900
After 30% federal ITC
Your savings
Difference
+$129,100
Estimated lifetime advantage
A $400/month electric bill in the US typically needs 55 solar panels (21.9 kW) at national average electricity rates and sun hours — $45,900 after the 30% ITC with 11.0-year payback. State-by-state, system size ranges from 6.6 kW in Hawaii to 37.1 kW in Washington, and payback spans 3.3–18.7 years.
Start here: National $400/month guide · Solar savings calculator · 3,500 sq ft by state
| Metric | US average ($400/mo bill) |
|---|---|
| Est. monthly usage | ~2,454 kWh |
| System size | 21.9 kW |
| Panels (400W) | 55 |
| Net cost after ITC | $45,900 |
| Simple payback | 11.0 years |
| 25-year savings | $129,100+ |
Formula: kW = Annual kWh ÷ (Peak sun hours × 365 × 0.82)
| Fastest payback | Slowest payback | |
|---|---|---|
| State | Hawaii | Washington |
| System | 6.6 kW · 17 panels | 37.1 kW · 93 panels |
| After ITC | $13,800 | $78,000 |
| Payback | 3.3 yrs | 18.7 yrs |
High electricity rates (e.g. Hawaii, California, Massachusetts) often beat sunny low-rate states for $400/month payback.
| State | System | Panels | After ITC | Payback |
|---|---|---|---|---|
| Alabama | 22.6 kW | 57 | $47,400 | 11.4 yrs |
| Alaska | 22.1 kW | 56 | $46,400 | 11.1 yrs |
| Arizona | 18.7 kW | 47 | $39,300 | 9.4 yrs |
| Arkansas | 27.0 kW | 68 | $56,600 | 13.6 yrs |
| California | 9.4 kW | 24 | $19,800 | 4.7 yrs |
| Colorado | 20.5 kW | 52 | $43,100 | 10.3 yrs |
| Connecticut | 15.4 kW | 39 | $32,300 | 7.7 yrs |
| Delaware | 24.1 kW | 61 | $50,600 | 12.1 yrs |
| Florida | 20.8 kW | 53 | $43,800 | 10.5 yrs |
| Georgia | 23.7 kW | 60 | $49,800 | 11.9 yrs |
| Hawaii | 6.6 kW | 17 | $13,800 | 3.3 yrs |
| Idaho | 29.2 kW | 73 | $61,200 | 14.7 yrs |
| Illinois | 23.4 kW | 59 | $49,100 | 11.7 yrs |
| Indiana | 25.5 kW | 64 | $53,500 | 12.8 yrs |
| Iowa | 29.9 kW | 75 | $62,900 | 15.1 yrs |
| Kansas | 24.3 kW | 61 | $51,000 | 12.2 yrs |
| Kentucky | 30.6 kW | 77 | $64,200 | 15.4 yrs |
| Louisiana | 26.1 kW | 66 | $54,700 | 13.1 yrs |
| Maine | 17.0 kW | 43 | $35,600 | 8.5 yrs |
| Maryland | 23.4 kW | 59 | $49,200 | 11.8 yrs |
| Massachusetts | 15.6 kW | 39 | $32,700 | 7.8 yrs |
| Michigan | 22.0 kW | 55 | $46,100 | 11.1 yrs |
| Minnesota | 24.1 kW | 61 | $50,600 | 12.1 yrs |
| Mississippi | 25.3 kW | 64 | $53,100 | 12.7 yrs |
| Missouri | 26.3 kW | 66 | $55,200 | 13.2 yrs |
| Montana | 26.7 kW | 67 | $56,100 | 13.4 yrs |
| Nebraska | 29.3 kW | 74 | $61,500 | 14.7 yrs |
| Nevada | 17.4 kW | 44 | $36,500 | 8.8 yrs |
| New Hampshire | 17.4 kW | 44 | $36,600 | 8.8 yrs |
| New Jersey | 20.7 kW | 52 | $43,500 | 10.4 yrs |
| New Mexico | 18.0 kW | 45 | $37,700 | 9.0 yrs |
| New York | 16.7 kW | 42 | $35,000 | 8.4 yrs |
| North Carolina | 24.1 kW | 61 | $50,600 | 12.1 yrs |
| North Dakota | 32.7 kW | 82 | $68,700 | 16.4 yrs |
| Ohio | 25.5 kW | 64 | $53,600 | 12.8 yrs |
| Oklahoma | 26.3 kW | 66 | $55,300 | 13.2 yrs |
| Oregon | 28.3 kW | 71 | $59,400 | 14.2 yrs |
| Pennsylvania | 22.7 kW | 57 | $47,700 | 11.4 yrs |
| Rhode Island | 15.2 kW | 38 | $31,800 | 7.6 yrs |
| South Carolina | 22.4 kW | 57 | $47,100 | 11.3 yrs |
| South Dakota | 28.1 kW | 71 | $59,000 | 14.1 yrs |
| Tennessee | 26.3 kW | 66 | $55,200 | 13.2 yrs |
| Texas | 20.8 kW | 52 | $43,600 | 10.4 yrs |
| Utah | 24.7 kW | 62 | $51,800 | 12.4 yrs |
| Vermont | 19.2 kW | 48 | $40,300 | 9.6 yrs |
| Virginia | 24.5 kW | 62 | $51,600 | 12.3 yrs |
| Washington | 37.1 kW | 93 | $78,000 | 18.7 yrs |
| West Virginia | 30.8 kW | 77 | $64,700 | 15.5 yrs |
| Wisconsin | 21.8 kW | 55 | $45,800 | 11.0 yrs |
| Wyoming | 27.9 kW | 70 | $58,600 | 14.0 yrs |
Estimates use EIA state rates, NREL sun hours, and 0.82 derate. National methodology.
$400/month maps to roughly 3,500 sq ft in national usage intensity — close to our 3,500 sq ft sizing tier.
| Sizing method | Best when you know… | National guide |
|---|---|---|
| Monthly bill (this page) | Utility bill amount | $400/mo |
| Home sq ft | House size | 3,500 sq ft |
Use both: if your bill differs from the sq ft estimate, trust your kWh usage from the utility statement.
Direct answers for US homeowners — sized for a $400/month electric bill.
Electricity rates and incentives vary — see data for your state.