Solar · Heating & hot water

How many solar panels to run a furnace?

A typical furnace uses about 4.80 kWh a day in the months you use it (about 180 days a year), based on 600 W for 8 hours a day, 180 days a year (864 kWh/yr). Off-grid with a battery, that takes about 2,330 W of solar panels (12 × 200 W) to keep up in December, the worst month in Tennessee (the middle state for sunshine), or 1,650 W in an average month, plus a battery of about 5,650 Wh. On a grid-tied home system it adds about 864 kWh a year: 0.59 kW, or 2 × 400 W panels.

Energy use4.80 kWh/dayper day of use
Off-grid panels2,330 Wworst month, Tennessee
Battery, 1 day5,650 Whpower station or lithium
Grid-tied2 × 400 W864 kWh/yr

Appliance energy: our furnace page (sources there) · solar: Global Solar Atlas 2.0 · solar data reviewed 2026-11-05

Can a panel and battery keep it running where you are?

Your situation: keeping a furnace running on solar. Different situation?

1

Your battery and panel

Battery size in

On the box: a station’s Wh is its battery; a panel’s W is its rated output. A 12 V 100 Ah battery is 1,200 Wh.

2

Where and how

Its motor needs about 800–2,500 W for a moment at start-up, so the inverter or power station must handle that surge; the panels don’t. Watts and hours for a different model or use: change them on the off-grid sizer, which adds up several appliances.

By state

Off-grid columns size the panels for the month named (with 85% charging and 85% inverter losses). The grid-tied column covers its yearly use on a home system.

Panels to run a furnace in every state
StateOff-grid, worst monthOff-grid, average monthGrid-tied, 400 W panels
Alabama2,110 W1,590 W2
Alaska10,200 W2,250 W2
Arizona1,520 W1,280 W2
Arkansas2,100 W1,600 W2
California1,760 W1,360 W2
Colorado1,660 W1,390 W2
Connecticut2,350 W1,660 W2
Delaware2,270 W1,660 W2
District of Columbia2,170 W1,650 W2
Florida1,780 W1,510 W2
Georgia2,020 W1,570 W2
Hawaii1,760 W1,450 W2
Idaho3,020 W1,520 W2
Illinois2,810 W1,700 W2
Indiana2,930 W1,730 W2
Iowa2,650 W1,680 W2
Kansas2,010 W1,550 W2
Kentucky2,670 W1,710 W2
Louisiana2,020 W1,570 W2
Maine2,620 W1,710 W2
Maryland2,250 W1,670 W2
Massachusetts2,460 W1,700 W2
Michigan3,670 W1,810 W2
Minnesota2,900 W1,720 W2
Mississippi2,080 W1,570 W2
Missouri2,230 W1,620 W2
Montana2,970 W1,650 W2
Nebraska2,270 W1,610 W2
Nevada1,590 W1,270 W2
New Hampshire2,480 W1,710 W2
New Jersey2,360 W1,690 W2
New Mexico1,470 W1,260 W2
New York2,320 W1,660 W2
North Carolina1,980 W1,580 W2
North Dakota3,010 W1,670 W2
Ohio3,250 W1,800 W2
Oklahoma1,880 W1,510 W2
Oregon4,060 W1,860 W2
Pennsylvania2,460 W1,710 W2
Rhode Island2,320 W1,670 W2
South Carolina1,920 W1,550 W2
South Dakota2,410 W1,610 W2
Tennessee2,330 W1,650 W2
Texas2,030 W1,600 W2
Utah2,480 W1,490 W2
Vermont3,730 W1,860 W2
Virginia2,020 W1,600 W2
Washington4,640 W1,880 W2
West Virginia2,970 W1,800 W2
Wisconsin2,970 W1,720 W2
Wyoming1,990 W1,460 W2

FAQ

How many solar panels to run a furnace?

A typical furnace uses about 4.80 kWh a day in the months you use it (about 180 days a year), based on 600 W for 8 hours a day, 180 days a year (864 kWh/yr). Off-grid with a battery, that takes about 2,330 W of solar panels (12 × 200 W) to keep up in December, the worst month in Tennessee (the middle state for sunshine), or 1,650 W in an average month, plus a battery of about 5,650 Wh. On a grid-tied home system it adds about 864 kWh a year: 0.59 kW, or 2 × 400 W panels.

Can a 200 W solar panel run a furnace?

Not on its own in Tennessee: even in the best month a 200 W panel puts back less than a typical furnace uses (4.80 kWh a day). It takes about 2,330 W to keep up all year, at 85% charging and 85% inverter efficiency. A panel alone can’t run it at night or under cloud; the battery does that.

What size battery do I need for a furnace on solar?

About 5,650 Wh to cover one day without sun (a day’s use ÷ 0.85 inverter efficiency, for a power station or lithium battery). Double it for lead-acid, which shouldn’t be run below half.

How many kWh does a furnace use a day?

About 4.80 kWh a day in the months you use it (about 180 days a year), based on 600 W for 8 hours a day, 180 days a year (864 kWh/yr). Your own use depends on the model and how you use it.

Sources and assumptions

Note: These are estimates; shading, roof direction, local weather, equipment and your installer’s design change the real output. We give no wiring or installation advice: follow your equipment’s manuals, and use a licensed installer for any system connected to your home’s wiring or the grid. Net metering and export credits are not modelled. Not financial or tax advice.

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