Assumes 3%/yr rate increases, 0.5%/yr panel degradation and no federal tax credit (the 30% §25D credit ended for systems installed after Dec 31, 2025). How we calculate
Data approachEIA rates · NREL sun hours · 2026 federal policy · methodology
A 3-ton central air conditioner running 8 hours a day needs about 14–20 solar panels (400 W each), depending on how sunny your location is. A 1.5-ton mini-split needs 5–7, and an 8,000 BTU window unit needs 3–4. The formula is simple, and the sections below show every input so you can run it for your own home.
Air conditioning is one of the biggest electricity loads in a US home. According to the U.S. Energy Information Administration (EIA), air conditioning accounted for about 19% of residential electricity use in 2020, and about 89% of homes use AC. The average US home uses roughly 10,500 kWh of electricity per year, or about 29 kWh per day. That is why sizing solar around cooling is a common starting point.
This guide covers central air conditioners, mini-splits, and window units. It separates two very different sizing problems: running an AC on solar during the day, and running it around the clock with batteries. It also reflects a major 2026 change: the federal residential solar tax credit is no longer available for newly installed homeowner-owned systems.
⚡ System Size
How Many Watts Does an Air Conditioner Use?
Start with the air conditioner’s real running wattage, not its BTU label. Running watts are roughly the unit’s cooling capacity in BTU per hour divided by its EER (energy efficiency ratio), so a more efficient unit draws less power for the same cooling.
AC type
Typical running watts
Daily kWh at 8 hours
Planning value used here
Window unit, 8,000 BTU
550–700 W
4.4–5.6 kWh
650 W → 5.2 kWh
Mini-split, 1.5-ton (inverter)
1,000–1,300 W
8–10.4 kWh
1,100 W → 8.8 kWh
Central AC, 2-ton
1,800–2,500 W
14.4–20 kWh
2,200 W → 17.6 kWh
Central AC, 3-ton
2,500–3,800 W
20–30.4 kWh
3,500 W → 28 kWh
The planning values are deliberately conservative hot-day figures. Real draw varies with SEER rating, outdoor temperature, and how often the compressor cycles. Check your unit’s nameplate or measure it with a plug-in or panel-level energy monitor for a precise number.
Daily energy is running watts times hours of operation. A 3,500-watt central AC running 8 hours uses 28 kWh, and that is the amount your array has to match to cover a full hot-day load.
One factor that matters mostly off-grid is startup surge. A compressor can briefly draw several times its running wattage when it starts. Grid-tied systems handle this automatically, but an off-grid inverter must be sized for the surge. Inverter-driven (variable-speed) and soft-start units reduce it considerably.
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⚡ System Size
How Many Solar Panels Do You Need to Run an AC?
Use this formula:
Panels needed = Daily AC kWh ÷ (Peak sun hours × 0.80 × Panel kW)
The 0.80 factor is a conservative derate for wiring, inverter, temperature, and soiling losses, so you do not need to add a separate buffer afterward. Peak sun hours are the daily solar energy a location receives, expressed as hours of full-strength sun. The values below are approximate annual averages based on NREL-derived data; look up your exact address with NREL’s PVWatts calculator or our solar system size calculator.
AC type (8 h/day)
Daily kWh
Arizona (6.5 h)
Texas (5.2 h)
Georgia (4.7 h)
New York (4.5 h)
Window unit
5.2
3
4
4
4
Mini-split, 1.5-ton
8.8
5
6
6
7
Central AC, 2-ton
17.6
9
11
12
13
Central AC, 3-ton
28.0
14
17
19
20
Worked example: a 3-ton central AC in Texas needs 28 ÷ (5.2 × 0.80 × 0.4) = 16.8, which rounds up to 17 panels.
Data visualization
Panels needed to cover 8 hours of AC use per day. A 3-ton central AC needs 14 panels in Arizona and 20 in New York. Calculated with 400 W panels and a 0.80 derate; sun hours are approximate NREL-derived averages.
Chart summary: AC type changes the panel count far more than location does. A 3-ton central AC needs 14 panels in Arizona and 20 in New York, a 43% increase. Yet the same cooling load delivered by a 1.5-ton mini-split needs only 5–7 panels anywhere in the table. If your goal is fewer panels, reducing the AC load usually beats chasing a sunnier location.
Two practical notes. First, 8 hours of full-load running is a hot-day planning case; across a whole year, AC runs less and the array also produces for other loads. Second, the figures above size for covering the entire cooling load. Many homeowners install a smaller array that offsets part of it. For example, a 4.0 kW array (10 panels) produces about 14 kWh per day on average at 4.5 sun hours, enough to cover a 1.5-ton mini-split on a hot day or roughly half of a 3-ton central AC’s 28 kWh. For a full cost breakdown by state and system size, see our guide to How Much Do Solar Panels Cost in 2026?.
⚡ System Size
Do You Need a Battery to Run AC on Solar?
Not for daytime cooling. A grid-tied system without batteries runs your AC directly from the panels in daylight and exports surplus power under your utility’s net metering or export program. At night, the AC draws from the grid like any other appliance. Be aware that standard grid-tied inverters shut down during a utility outage, so panels alone will not keep the AC running in a blackout.
Batteries become necessary if you want to run AC after dark, ride through outages, or avoid expensive evening grid rates. Here is the sizing math for a 3.5 kW central AC, assuming the compressor cycles on about 50% of the time (adjust for your climate and home):
Overnight, 8 hours: 3.5 kW × 8 h × 0.50 = about 14 kWh, roughly one Tesla Powerwall 3 (13.5 kWh usable, per Tesla’s specifications)
Around the clock, 24 hours: 3.5 kW × 24 h × 0.50 = about 42 kWh, roughly three to four Powerwall-class batteries, plus an array large enough to generate that energy and recharge the batteries each day
Off-grid inverter: it must handle the compressor’s startup surge, not just its running watts
Because battery costs vary widely by brand, installer, and region, get itemized quotes rather than relying on a rule of thumb. Note that the federal credit that previously covered home batteries also ended for systems placed in service after 2025.
The most cost-effective approach for most households is to size the array for daytime cooling, add a battery only if you need evening or backup power, and stay grid-connected for overnight loads. Storage pays off fastest where utilities charge time-of-use rates or pay little for exported solar. California, for example, shifted to lower export credits under its NEM 3.0 rules in 2023, which raises the value of using your own solar power. Model your options with the battery storage calculator, and see our payback period by state guide.
⚡ System Size
How Do SEER Ratings and Mini-Splits Reduce Panel Count?
SEER (Seasonal Energy Efficiency Ratio) measures cooling output per unit of electricity over a season. Because electricity use is inversely proportional to efficiency, replacing a SEER-14 unit with a SEER-20 unit of the same capacity cuts consumption by about 30% (1 − 14 ÷ 20), and the panels needed to offset it drop by the same proportion. Since January 2023, U.S. Department of Energy efficiency standards for residential central air conditioners are regional and use the SEER2 test method, with a higher minimum in southern states than in northern ones.
Inverter-driven mini-splits are the most solar-friendly option. Their variable-speed compressors ramp up and down instead of cycling at full power, which produces a steadier, lower draw that matches a solar array’s daytime output well. They are also ductless. According to ENERGY STAR, a typical home duct system loses roughly 20–30% of the air moving through it to leaks, so ductless units avoid that loss entirely.
The panel savings are large when a smaller unit genuinely meets your needs. Using the table above, in Georgia a 3-ton central AC needs 19 panels while a 1.5-ton mini-split needs 6. That comparison only holds if the mini-split can cool the space you care about; whole-home cooling usually needs several zones, and each added zone adds load. Use a load calculation (Manual J) from an HVAC contractor before downsizing.
On the panel side, residential modules commonly range from about 370 to 440 W. Higher-wattage panels cost more per panel but mean fewer panels, fewer roof penetrations, and less racking, which helps on small roofs. The panel counts in this guide scale directly: with 440 W panels instead of 400 W, divide the 400 W count by 1.1.
💰 System Cost
How Much Does Solar for AC Cost in 2026?
The biggest change for 2026 is incentives. The 30% Residential Clean Energy Credit (Section 25D) that homeowners used to claim for purchased solar systems ended for property placed in service after December 31, 2025. A homeowner-owned system installed in 2026 does not qualify for it. Third-party-owned systems (leases and power purchase agreements) may still pass along savings from a business tax credit under Section 48E, but terms, eligibility deadlines, and contract risks vary, so read those agreements carefully.
Installed prices differ by region, equipment, and installer, so we show a transparent scenario rather than a single “average” price. The table below uses a 4.0 kW system (about 10 panels) that produces roughly 5,256 kWh per year (4.0 kW × 4.5 sun hours × 0.80 × 365 days). It shows simple payback, which is the system cost divided by first-year bill savings, with no incentives.
Installed price
System cost
12¢/kWh
16¢/kWh
20¢/kWh
30¢/kWh
$2.50/W
$10,000
15.9 yrs
11.9 yrs
9.5 yrs
6.3 yrs
$3.00/W
$12,000
19.0 yrs
14.3 yrs
11.4 yrs
7.6 yrs
$3.50/W
$14,000
22.2 yrs
16.6 yrs
13.3 yrs
8.9 yrs
The $/W prices and the electricity rates are planning assumptions for illustration, not market statistics. Replace them with your own quotes and your utility rate.
Data visualization
Simple payback of a 4.0 kW add-on system by electricity rate (years). At $3.00/W, payback is 19.0 years at 12 cents per kWh and 7.6 years at 30 cents. Assumes 5,256 kWh/yr, no incentives, flat rates. Source: our calculation.
Chart summary: Your electricity rate matters more than the installed price. At $3.00/W, payback falls from about 19 years at 12¢/kWh to about 7.6 years at 30¢/kWh. A $1,000 swing in system cost moves payback by roughly 1–2 years, but doubling your electricity rate roughly halves it. That is why heavy-cooling homes in high-rate utility territories see the strongest returns.
Over 25 years, and assuming 0.5% annual panel degradation with flat 16¢/kWh rates, the same $12,000 system would offset about 123,800 kWh, worth roughly $19,800. That is about $7,800 more than it cost, before any state incentives and before any future rate increases, which would improve the result.
Data visualization
Cumulative cash flow of a 4.0 kW system over 25 years (USD). Break-even comes in year 15 with no incentives and year 11 with a 3,000 dollar New York credit, ending at 7,810 and 10,810 dollars. Assumes 16 cents per kWh flat and 0.5 percent annual degradation. Source: our calculation.
Chart summary: With no incentives, the cumulative line crosses zero in year 15 (slightly later than the 14.3-year simple payback because panels lose output each year) and reaches about $7,810 by year 25. The orange line shows a $3,000 New York credit pulling break-even forward to year 11. Both lines use 16¢/kWh for comparison only; actual New York rates differ, so run your own numbers.
State incentives can shorten payback. New York offers a 25% state income tax credit up to $5,000, and Arizona offers 25% up to $1,000 (Arizona Form 310). On the $12,000 illustration, the New York credit would be $3,000 (net $9,000, about 10.7 years at 16¢/kWh), and the Arizona credit would be capped at $1,000 (net $11,000, about 13.1 years). Those two figures use the same 16¢ rate only for comparison; actual local rates differ. Check your state’s current rules, because credits, caps, and deadlines change. You can estimate yours with the solar tax credit calculator.
If you are replacing an aging air conditioner at the same time, pairing a new high-efficiency unit or mini-split with a right-sized array lets you shrink the solar system you need. Get at least three local quotes, ask each installer to state price per watt, and compare equipment warranties.
Solar vs utility company · 25-year comparison
25-year totals: 3%/yr rate increases, 0.5%/yr degradation, no federal credit. Methodology
All panel counts and paybacks above are our own calculations from the stated assumptions: 400 W panels, a 0.80 system derate, approximate annual-average peak sun hours (Arizona 6.5, Texas 5.2, Georgia 4.7, New York 4.5), and the AC running-watt planning values in the first table. They are estimates, not guarantees; your results depend on roof orientation, shading, equipment, and local rates.
Arizona Department of Revenue Form 310 and New York State Department of Taxation and Finance residential solar credit instructions
U.S. Department of Energy and ENERGY STAR guidance on central air conditioner standards and duct leakage
This article is general information, not tax, legal, or financial advice. Confirm incentive eligibility with a tax professional and get written installer quotes before you buy.
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Direct answers for US homeowners — sized for a $75/month electric bill.
A 3-ton central AC drawing about 3.5 kW for 8 hours uses roughly 28 kWh. With 400-watt panels and a 0.80 system derate, that takes about 14 panels in Arizona (6.5 sun hours), 17 in Texas (5.2), 19 in Georgia (4.7), and 20 in New York (4.5). A 2-ton unit needs about 9–13 panels.
A 1.5-ton inverter mini-split drawing about 1.1 kW for 8 hours uses roughly 8.8 kWh, which takes 5–7 panels depending on location. An 8,000 BTU window unit at about 650 W uses roughly 5.2 kWh over 8 hours and needs 3–4 panels. Both assume 400-watt panels and a 0.80 derate.
Yes, during daylight. A grid-tied system powers the AC directly from the panels and exports any surplus. The limits: it does not run the AC at night unless the grid supplies it, and standard grid-tied inverters shut down during a grid outage unless you add a battery or backup-capable inverter.
For 8 overnight hours with a 3.5 kW central AC cycling at about 50% duty, plan on roughly 14 kWh, about one Tesla Powerwall 3 (13.5 kWh usable). Running the same unit around the clock off-grid needs about 40+ kWh of storage plus a larger array and an inverter that handles compressor startup surge.
It can be, but payback is longer. The 30% federal credit for homeowner-owned systems ended Dec 31, 2025. In our illustration, a 4.0 kW system at $3.00/W pays back in about 14 years at 16¢/kWh, or about 8 years at 30¢/kWh. High electricity rates, heavy cooling use, and state credits (NY, AZ) improve the math.
Same usage, bill-based guide
Your AC add-on system target maps to roughly a $75/month electric bill nationally.
18.19¢/kWh — US average residential price. Source: EIA Electric Power Monthly, Table 5.6.B (year-to-date through July 2026), residential average retail price (July 2026) (EIA)
Solar production
4.5 peak sun hours/day × 0.82 system derate. Approximate state-average daily solar resource (peak sun hours) based on NREL solar resource data (NSRDB); not location-specific — use NREL PVWatts for an address-level estimate. (NREL PVWatts)
Installed price
$3.00 per watt before incentives. Blended 2026 US residential installed price used by this site; EnergySage marketplace reported about $2.60/W (mid-2026); full-market medians are higher.
Federal tax credit
$0 for homeowner-owned systems installed in 2026 — the 30% §25D credit ended Dec 31, 2025 (IRS)
Net metering
National blend — solar assumed to offset 75% of the bill (87% in full-retail net-metering states, 55–70% elsewhere).
Estimates only — not tax, legal or financial advice. Get at least three installer quotes and confirm incentives with your utility and a tax professional.