How Many Solar Panels Does a Tiny Home Need?

Most people answer this question by looking at what somebody else installed on YouTube. That’s how you end up with four panels on a house that needed six, or six on a house that needed three.

The actual answer comes from one calculation, and it takes about five minutes. You need three numbers: how much power you use in a day, how much sun your location gets, and how big the panels are. Everything else is multiplication.

Here’s the whole method, with a real worked example you can follow line by line, plus a chart if you just want the ballpark and a battery bank calculation at the end — because panels without enough storage is the other half of this mistake.

Short answer if you’re in a hurry: most tiny homes need 3 to 6 panels at 400 watts each — a 1,200W to 2,400W array — paired with a 6 to 12 kWh battery bank. Now here’s how to find your number instead of that one.

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Step 1 — Add up your daily watt-hours

List every electrical device in the house. For each one: watts × hours used per day = watt-hours per day. Add them all up.

Wattage is printed on the device, on its power brick, or in the manual. If you can’t find it, a $25 plug-in meter will tell you exactly, and it’s the best money you’ll spend on this whole project.

Here’s a realistic example for a small off-grid home that cooks and heats with propane:

Device	Watts	Hours/day	Watt-hours/day
LED lighting (6 fixtures)	48	5	240
12V refrigerator	50	12	600
Laptop + monitor	80	6	480
Phone and tablet charging	20	3	60
WiFi router / modem	12	24	288
Water pump (12V)	60	0.75	45
Roof vent fan	35	8	280
Propane furnace blower	40	4	160
TV	60	3	180
Electric kettle / Instant Pot	700	0.5	350
Vacuum, tools, occasional loads	200	0.5	100
Phantom draws and miscellaneous	—	—	200
Daily total			2,983 Wh

Two notes on that table. The fridge only counts 12 hours because the compressor cycles — it isn’t running all 24. And the “phantom draws” line is not padding; every device with a standby light is pulling something around the clock, and it adds up to more than people expect.

Where most homes land: 2–3 kWh/day for a minimal setup with propane cooking and heat, 3–5 kWh/day for a typical build, and 6–8+ kWh/day once you add a mini-split or induction cooking.

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Step 2 — Add system losses

Your panels do not deliver their rated output to your outlets. You lose energy in the inverter, in the wiring, in the charge controller, and to heat.

Multiply your daily total by 1.3.

2,983 Wh × 1.3 = 3,878 Wh/day adjusted

That 30% is the standard real-world derate, and skipping it is the single most common reason off-grid systems underperform. If you size to 2,983 you have built a system that is a third too small and you will spend a year wondering why.

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Step 3 — Find your peak sun hours

Peak sun hours are not hours of daylight. It’s the equivalent number of hours of full-strength (1,000 W/m²) sun your location receives, averaged out. A place with 14 hours of weak winter daylight might only have 3 peak sun hours.

Most of the continental US falls between 4 and 6 peak sun hours annually. The desert Southwest runs at the top of that. The Pacific Northwest and the Great Lakes run at the bottom, closer to 3–4. Everywhere else sits in the middle.

Look up your exact figure on NREL’s PVWatts Calculator — it’s free, it’s the industry standard, and it takes thirty seconds.

Important: if you’re living there year-round, size against your worst month, not the annual average. December peak sun hours can be half the June figure. A system sized on the annual average will leave you running a generator all winter.

We’ll use 4.5 for the example.

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Step 4 — Calculate the array

Array watts = adjusted daily watt-hours ÷ peak sun hours

3,878 ÷ 4.5 = 862 watts minimum

Then add a buffer for cloudy stretches, panel aging, dust, and the fact that your loads will grow — they always grow. Multiply by 1.25.

862 × 1.25 = 1,077 watts recommended

Divide by your panel wattage and round up.

1,077 ÷ 400W panels = 2.69 → 3 panels

So: three 400W panels, about 1,200W of array. Or six 200W panels if roof geometry favors smaller ones — same total, more mounting hardware.

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Step 5 — Size the battery bank

Panels charge. Batteries carry you through the night and the bad week. This is where undersizing actually hurts.

Battery kWh = (adjusted daily use × days of autonomy) ÷ usable depth of discharge

Use 0.8 for LiFePO4 (lithium iron phosphate). Lead-acid is 0.5 and you’ll need nearly double the nameplate capacity for the same usable energy — which is why LiFePO4 has become the default despite the higher sticker price.

Two days of autonomy is the practical minimum. Three is comfortable if you live somewhere with real winters.

(3,878 Wh × 2 days) ÷ 0.8 = 9,695 Wh ≈ a 9.7 kWh battery bank

At three days: 14.5 kWh

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The quick sizing chart

If you don’t want to do the math, find your daily use here. Assumes 4.5 peak sun hours, 30% system losses, and a 25% buffer.

Your daily use	Minimum array	Recommended array	400W panels	200W panels	Battery (2 days)
1.5 kWh	435 W	545 W	2	3	4.9 kWh
2 kWh	580 W	725 W	2	4	6.5 kWh
3 kWh	865 W	1,085 W	3	6	9.8 kWh
4 kWh	1,155 W	1,445 W	4	8	13.0 kWh
5 kWh	1,445 W	1,805 W	5	10	16.3 kWh
6 kWh	1,735 W	2,165 W	6	11	19.5 kWh
8 kWh	2,310 W	2,890 W	8	15	26.0 kWh

Fewer peak sun hours than 4.5? Scale up proportionally — at 3.5 hours you need about 30% more panel.

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The three things that ruin an otherwise correct calculation

Flat-mounted panels. Panels lying flush on a flat roof lose roughly 10–15% compared to a tilted array aimed at the sun. Tilt if you can, and add panel if you can’t.

Heat. Panels lose about 0.3–0.4% of output per °C above 25°C. On a 40°C roof in July that’s a real 5–6% off the top. Leave an air gap under roof-mounted panels — it matters more than people think.

Shade. One branch across one panel can drag down an entire string wired in series. Watch the site across a full day before you commit to a mount location, and consider parallel wiring or optimizers if partial shade is unavoidable.

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What about the rest of the system?

Panels are one of four components, and the other three have to match.

Charge controller: MPPT, not PWM. MPPT harvests 20–30% more in cold and low-light conditions, and the price gap has largely closed.

Inverter: size it for your largest simultaneous load, and check the surge rating against your water pump and any compressor. Pure sine wave only.

Wiring: correct gauge for the run length and the amperage, properly fused. This is the cheapest part of the system and the one that causes fires.

If you’d rather skip the component-by-component build for now, a good all-in-one solar generator with a matched solar panel kitAs an Amazon Associate I earn from qualifying purchases. Some links on this page are affiliate links. If you click and make a purchase, I may earn a commission at no extra cost to you. covers a modest 1–2 kWh/day load out of the box, and works as a backup once you build the full system.

Wondering what the whole system costs? Every line — panels, batteries, inverter, and the rest of the off-grid stack — is broken down in our 2026 off-grid tiny home cost guide.

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FAQ

How many solar panels for a 400 sq ft tiny home?
Square footage doesn’t determine it — your appliances do. A 400 sq ft home with propane heat and cooking might need 3 panels; the same house with a mini-split and an induction cooktop needs 6–8. Run the load calculation.

Can 2 solar panels run a tiny house?
Two 400W panels (800W) supports roughly 1.5–2 kWh per day at 4.5 peak sun hours. That’s lights, a 12V fridge, laptop, phones, fans, and a water pump — a genuinely minimal but livable setup with propane doing the cooking, heating, and hot water.

How many batteries do I need for a tiny house solar system?
Most tiny homes need 6 to 12 kWh of LiFePO4 for two days of autonomy. The full spec matrix is in our off-grid utilities checklist. Divide by the capacity of the batteries you’re buying — a common 5.1 kWh server-rack unit means two of them for most builds.

Do solar panels work in winter?
They work, and they’re actually more efficient in cold air — the problem is fewer peak sun hours and snow cover. That’s why you size against your worst month, not the annual average.

Is a solar generator enough for a tiny home?
For a weekend cabin or a very light load, yes. For full-time living, a 1–2 kWh portable unit will run short — but it makes an excellent backup and a good way to start before committing to a full system.

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