8kW Solar System: Yearly Output, Panels Needed and 2026 Cost
Short answer
An 8kW solar system makes about 8,800 to 12,800 kWh a year in most of the US, or roughly 24 to 35 kWh a day. That is close to what a typical American home buys from the grid. You need about 19 panels at 430 W and 450 to 550 square feet of usable roof. Installed cost is typically $17,600 to $25,600 in late 2026, with no federal homeowner credit.
Eight kilowatts is the size installers quote most often to ordinary family homes: three or four bedrooms, central air, a gas or electric furnace, and no electric car yet. At the US middle value of 4.5 peak sun hours, it produces almost exactly what the average household uses in a year.
Whether an 8kW solar system wipes out your whole bill depends on your region’s sun and your state’s typical use. This page covers both, then the panel count, 2026 price, payback, inverter and battery choices.
Is 8kW the right size for an average American home?
For a home near the national average, yes. The US Energy Information Administration puts the average residential customer at about 10,791 kWh a year, close to 900 kWh a month. Here is what 8 kW of panels makes with this site’s standard assumptions of 4.5 peak sun hours and 80% system efficiency:
Example: 8 × 4.5 × 0.80 = 28.8 kWh a day; 28.8 × 365 = 10,512 kWh a year
That covers about 97% of the 10,791 kWh average. You can also run the sum backward from your own bills. Add up 12 months of kWh, then divide by the energy one kilowatt of panels makes where you live.
Example: 10,800 ÷ (4.5 × 0.80 × 365) = 10,800 ÷ 1,314 = 8.2 kW
The how many solar panels calculator does the same sum with your own usage and sun hours.
Will an 8kW system cover 100% of your bill where you live?
The national average hides big regional gaps. Southern homes run air conditioning for months and use far more power, while mild coastal states use much less. The table pairs 8 kW output in sample cities with the 2024 average use per home in that state, taken from EIA’s electricity sales and revenue tables (average monthly kWh × 12).
| City | Peak sun hours | 8 kW output per year | State average use per home | Share covered |
|---|---|---|---|---|
| Phoenix, AZ | 6.3 | 14,717 kWh | 12,899 kWh | 114% |
| Los Angeles, CA | 5.5 | 12,848 kWh | 6,038 kWh | 213% |
| Denver, CO | 5.3 | 12,381 kWh | 8,091 kWh | 153% |
| Dallas, TX | 5.0 | 11,680 kWh | 13,154 kWh | 89% |
| Chicago, IL | 4.4 | 10,278 kWh | 8,317 kWh | 124% |
| Seattle, WA | 3.7 | 8,643 kWh | 11,465 kWh | 75% |
| US middle value | 4.5 | 10,512 kWh | 10,359 kWh | 101% |
Sun hours are approximate annual averages for south-facing panels tilted near latitude. State figures are electricity bought from the utility, so they understate real use in states with lots of rooftop solar, such as California and Arizona.
What the table tells a typical family
- Texas, the Southeast and other hot, humid states: average homes use 1,000 to 1,200 kWh a month, so 8 kW usually covers about 75% to 95% of the bill. Full coverage takes 9 to 10 kW.
- The Northeast, Midwest and Mountain West: homes often use 550 to 850 kWh a month. Here 8 kW tends to overshoot, and 5 to 7 kW may be enough unless you plan to add electric heat or a car.
- California: the average purchase is only about 500 kWh a month, so 8 kW is usually oversized for today’s use and should be justified by future loads.
- The Pacific Northwest: low sun hours plus electric heating mean 8 kW covers only about three quarters of an average Washington bill.
Covering 100% on paper also assumes your utility credits summer surplus against winter bills. Under annual net metering it does. Under export rates well below retail, a system that makes 100% of your kWh may cancel only about 60% of the dollars, as the payback table below shows. Model your own tariff with the net metering calculator.
How many panels and how much roof does 8 kW take?
Divide 8,000 watts by the panel rating and round up. The rounded array usually ends slightly above 8 kW, which is normal.
| Panel rating | Panels | Array size | Panel area (approx.) |
|---|---|---|---|
| 400 W | 20 | 8.0 kW | about 420 sq ft |
| 430 W | 19 | 8.17 kW | about 400 sq ft |
| 450 W | 18 | 8.1 kW | about 390 sq ft |
The area comes from panel efficiency. Current residential modules convert roughly 20% to 22% of sunlight.
Example: 8,000 ÷ (1,000 × 0.22) = 36.4 m², about 391 sq ft. At 20%: 40 m², about 431 sq ft
Add fire-code pathways, ridge setbacks and space around vents, and you need about 450 to 550 square feet of usable roof. Many family homes fit all 19 panels on one south, east or west plane; a broken-up hip roof may need two planes, which affects the inverter choice below.
How much does an 8kW solar system cost in 2026?
Typical US installed prices in late 2026 run about $2.20 to $3.20 per watt before state or utility incentives. Permits, design, interconnection paperwork and the crew’s travel cost about the same whether the job is 6 kW or 12 kW. On an 8 kW job those fixed costs are spread over fewer watts, so quotes often land in the middle or upper part of the range.
| Price per watt | 8 kW installed | What usually drives it |
|---|---|---|
| $2.20 | $17,600 | One simple roof plane, busy local market |
| $2.60 | $20,800 | Middle of the market |
| $3.20 | $25,600 | Two or more roof planes, premium panels, high-cost metro |
The 30% federal residential clean energy credit (Section 25D) does not cover homeowner-owned systems installed after December 31, 2025, so budget the full price. Some states and utilities still offer rebates. Leases and power purchase agreements follow different business rules, so check any credit a contract mentions with a tax adviser. To test a quote, enter your own price per watt in the solar panel cost calculator.
How long does an 8kW system take to pay for itself?
The example uses a $20,800 system producing 10,512 kWh a year and the 2024 US average residential price of about 16.5 cents per kWh from the same EIA tables.
Example with full net metering: 10,512 × $0.165 = $1,734 a year; $20,800 ÷ $1,734 = 12.0 years
| Billing scenario | Yearly savings | Simple payback |
|---|---|---|
| Full net metering at $0.165 | $1,734 | 12.0 years |
| 40% used at home at $0.165, 60% exported at $0.06 | $1,072 | 19.4 years |
| Full net metering at $0.30 | $3,154 | 6.6 years |
| 40% used at home at $0.32, 60% exported at $0.08 | $1,850 | 11.2 years |
The 40/60 split is an assumption for a family that is out at work and school during the day. The figures ignore rate rises, panel degradation and maintenance.
Can one inverter handle an 8kW solar system?
Yes, and this is where 8 kW has a practical advantage over bigger arrays. A single 7.6 kW split-phase string or hybrid inverter is the common match. With 19 panels at 430 W (8.17 kW DC), the DC-to-AC ratio is about 1.07, so the inverter will rarely clip.
Why 7.6 kW fits a standard 200 A panel
Most family homes have a 200 A main panel with a 200 A main breaker. The NEC 120% rule lets the solar breaker plus the main breaker add up to 120% of the busbar rating, as long as the solar breaker sits at the opposite end of the bus from the main.
Example: (200 × 1.2) − 200 = 40 A. Inverter: 7,600 W ÷ 240 V = 31.7 A × 1.25 = 39.6 A, which fits a 40 A breaker
That is why so many 7 to 8.5 kW quotes come without a panel upgrade, while a 15 kW home often needs one. Older houses with a 100 A panel are the exception: (100 × 1.2) − 100 leaves only 20 A, enough for about 3.8 kW of inverter. Those homes need a supply-side connection, a derated main breaker or a new panel. Your installer and local inspector make the final call, and the inverter size calculator checks the ratio and current for other combinations.
String inverter or microinverters?
If all 19 panels share one unshaded roof face, a string inverter with two MPPT inputs is the cheapest route, with the panels split into two strings such as 10 and 9. If the panels sit on two or three roof planes or a tree shades part of the roof in the afternoon, microinverters (one per panel) keep the shaded panels from dragging the rest down. The same 40 A limit applies to their combined AC output: about 32 A of continuous current, or roughly 7.7 kW at 240 V.
What battery pairs well with an 8kW system?
Size the battery to the energy you use after sunset, not to the array. An average home uses about 29.6 kWh a day (10,791 ÷ 365). If roughly 40% of that falls in the evening and overnight, that is about 11.8 kWh. This site assumes 90% usable capacity.
Example: 11.8 ÷ 0.90 = 13.1 kWh of battery
The array also has to refill that battery. On a 4.5 sun-hour day, 8 kW makes 28.8 kWh. If the house uses the other 60% of its 29.6 kWh (about 17.8 kWh) in daylight, the surplus is 28.8 − 17.8 = 11.0 kWh, almost exactly the usable capacity of a 13 kWh battery.
| Battery size | Usable at 90% | What it does with 8 kW of panels |
|---|---|---|
| 10 kWh | 9.0 kWh | Covers about three quarters of assumed evening use; refills on most sunny days |
| 13 to 15 kWh | 11.7 to 13.5 kWh | Covers assumed evening use; refills on an average day |
| 20 kWh | 18.0 kWh | Adds outage reserve, but an average day’s surplus will not fill it |
On a winter day with an assumed 2.5 sun hours, the same array makes 8 × 2.5 × 0.80 = 16 kWh, less than the house uses in daylight, so the battery will not refill from solar alone. A 10 kWh unit, covered in our guide to 10kWh batteries, suits families who mainly want backup for the fridge, lights, internet and furnace fan. Bigger evening loads need the battery calculator and your own hourly data.
When is 8kW the wrong size for a family home?
Plan for the next five years, not just last year’s bill.
- An electric car is coming. At 12,000 miles a year and 0.30 kWh per mile, an EV adds 3,600 kWh. A 10,791 kWh home becomes 14,391 kWh, and 14,391 ÷ 1,314 = about 11 kW at the US middle value. Our 15kW solar system guide covers homes that add an EV and a heat pump together.
- You use well below average. A Los Angeles home using 6,000 kWh a year needs only 6,000 ÷ (5.5 × 0.80 × 365) = 3.7 kW. Where exports earn little, the extra panels on an 8 kW system pay back slowly.
Frequently asked questions
How many kWh a month does an 8kW solar system produce?
About 730 to 1,070 kWh a month averaged over the year in most of the US, based on 8,800 to 12,800 kWh a year. At 4.5 peak sun hours it is about 864 kWh a month. Summer months produce well above the average and December well below it.
Is an 8kW solar system enough for a 2,000 square foot house?
Often, but floor area is a weak guide. The average Texas home buys about 13,150 kWh a year, while the average Colorado home buys about 8,100, and house size explains only part of that gap. Size from 12 months of bills: divide yearly kWh by 1,314 for the US middle value.
Do I need a new electrical panel for an 8kW solar system?
Usually not if you have a 200 A panel with a 200 A main breaker. A 7.6 kW inverter needs a 40 A breaker, which is the most the NEC 120% rule allows on that panel. Homes with a 100 A panel normally need an upgrade or a supply-side connection.
Can an 8kW solar system run central air?
Yes, on a grid-tied system. A 3,000 W air conditioner running 8 hours uses 24 kWh, and 8 kW makes about 29 kWh on an average day, so on a sunny day the array covers much of the cooling load. Running it through a power cut requires a battery and an inverter able to handle the compressor’s startup surge.
Can I go off grid with an 8kW solar system?
Only with a frugal, mostly gas-heated home and a large battery bank. Two days of storage at 30 kWh a day means 30 × 2 ÷ 0.90 = 67 kWh of battery, and short winter days produce far less than the yearly average. Most families keep the grid connection and add a 10 to 15 kWh battery.
