How many watts of solar do I need to fully recharge a typical RV battery bank?

It depends entirely on your daily energy use and your local sun hours, not on the battery bank size alone. Add up your loads with a daily energy budget calculator to get a watt-hour target, then use the array size table above at your region's published sun hours to find the panel wattage. Two rigs with identical battery banks can need very different arrays if their daily draw differs.

Why is realistic solar output lower than the nameplate wattage?

Nameplate wattage is measured under lab standard test conditions that a roof-mounted panel almost never experiences in the field. Panel heat reduces output, a flat RV roof cannot tilt toward the sun the way a ground-mounted panel can, and wiring and charge controller conversion both lose a little more. The 0.75 derate used on this page is a commonly applied planning convention that bundles those losses into one number.

What counts as a peak sun hour?

A peak sun hour is the equivalent of one hour of sunlight at full intensity, 1,000 watts per square meter. A location's daily total is expressed as an equivalent number of these hours rather than as literal daylight hours, because real sunlight varies through the day from dawn to solar noon to dusk. It is genuinely published data per region, not a rule of thumb.

Does cloudy weather ruin solar charging?

It reduces output substantially but rarely to zero, since diffuse light still reaches the panel. The published peak sun hour figures for a region already account for typical cloud cover across a season, which is why winter figures run well below summer figures in the same location. A single unusually overcast day will underperform even the winter average.

Is 100 watts of solar per 100 amp-hours of battery a reliable rule?

It is a widely repeated planning convention and nothing more precise than that. It ignores your actual daily draw and your actual sun hours, both of which vary enormously between a weekend camper and a full-time boondocker, or between the desert Southwest and the Pacific Northwest. Use it only as a rough sanity check, and size the real array from a daily energy budget and a location's published sun hours instead.

Does 24V solar wiring change how much energy I get?

No. The array's watt-hour output depends on panel wattage, sun hours, and derate, none of which involve system voltage. What changes at 24V is the current on the battery side of the charge controller, which is half of what it would be at 12V for the same power, meaning thinner controller-to-battery cable can carry it within the same voltage drop limit.

Reference

RV Solar Panel Daily Output Chart by Sun Hours

Researched from published standards and manufacturer specifications. Updated 2026-09-17.

Quick answer

Daily output is panel watts x peak sun hours x a system derate, commonly 0.75 for real-world losses, a labeled convention rather than a spec. 100W of panel at 5 peak sun hours gives 500Wh nameplate but about 375Wh realistic, which is 31.3Ah at 12V. Peak sun hours is not daylight hours; it is a published equivalent figure for a location, and this page scales generically so you can apply your own regional number.

A solar panel's nameplate wattage is measured under lab test conditions that a roof-mounted panel rarely sees in the field. Panel heat, an RV roof that cannot be tilted toward the sun, wiring loss, and charge controller efficiency all take a share, which is why this site applies a 0.75 derate as a planning convention on top of the nameplate math. That derate is not a published specification the way NEC resistance figures are; it is a commonly used real-world adjustment, and the tables below label it every time it appears.

Peak sun hours is the other half of the equation and it is genuinely published data, not a convention. It is not the number of daylight hours in a day; it is the equivalent number of hours at full solar intensity that would deliver the same total energy as the actual, variable sun through the day. The peak sun hours by region chart has the published regional figures. This page scales output generically per 100W across a range of sun-hour values so you can plug in whatever number applies to where you actually camp.

How much energy does 100W of solar actually make in a day?

This is the base unit every other table on this page scales from. Nameplate is watts times sun hours with no derate. Realistic is the same figure at the 0.75 convention.

Daily output per 100W of panel, by peak sun hours
Sun hours	Nameplate Wh	Realistic Wh (0.75 derate)	Realistic Ah at 12V	Realistic Ah at 24V
1	100	75.0	6.3	3.1
2	200	150.0	12.5	6.3
3	300	225.0	18.8	9.4
4	400	300.0	25.0	12.5
5	500	375.0	31.3	15.6
6	600	450.0	37.5	18.8
7	700	525.0	43.8	21.9
8	800	600.0	50.0	25.0

Convention Source: Nameplate wattage x sun hours is arithmetic; the 0.75 system derate is a commonly used planning convention for panel heat, wiring loss, controller efficiency and imperfect roof aim, not a published specification. Find your location's published peak sun hours on the peak sun hours by region chart, then scale this table to your actual array size.

Scaling to common array sizes at 5 peak sun hours

5 peak sun hours is a reasonable mid-range planning figure across much of the continental US on an annual basis, and it is what this table uses to show realistic output at common array sizes. Substitute your own regional figure for a more exact number.

Realistic daily output at 5 peak sun hours, by array size (0.75 derate)
Array size	Realistic Wh	Realistic Ah at 12V
100W	375.0	31.3
200W	750.0	62.5
300W	1125.0	93.8
400W	1500.0	125.0
600W	2250.0	187.5
800W	3000.0	250.0
1200W	4500.0	375.0

Convention Source: Array watts x 5 sun hours x 0.75 derate. The 5 sun hour figure is a representative planning value, not this array's actual location..

How long does it take a 100W array to replace a specific energy deficit?

Recharge time is the deficit in watt-hours divided by array watts times the derate, using full-sun equivalent hours rather than calendar hours. A cloudy afternoon spreads the same equivalent hours over more real clock time.

Recharge time per 100W of array, at 0.75 derate (full-sun equivalent hours)
Energy deficit	Recharge time
100Wh	1.3 hours
200Wh	2.7 hours
500Wh	6.7 hours
1000Wh	13.3 hours
1500Wh	20.0 hours

Convention Source: Deficit Wh / (100W x 0.75 derate). Scale the hours down in proportion to a larger array..

What array size covers a given daily energy budget?

This table runs the same math in reverse: for a daily energy budget in watt-hours, how many array watts are needed at a given sun-hour figure. Round up to the next available panel or kit size.

Array watts needed for a daily energy budget, by sun hours (0.75 derate)
Daily budget	3 sun hours	4 sun hours	5 sun hours	6 sun hours	7 sun hours
200Wh	89W	67W	53W	44W	38W
400Wh	178W	133W	107W	89W	76W
600Wh	267W	200W	160W	133W	114W
800Wh	356W	267W	213W	178W	152W
1200Wh	533W	400W	320W	267W	229W
1600Wh	711W	533W	427W	356W	305W
2000Wh	889W	667W	533W	444W	381W

Convention Source: Array watts = daily Wh / (sun hours x 0.75 derate). Run your own daily budget from the daily energy budget calculator for an exact figure..

Why peak sun hours, not daylight hours, is the number that matters

A location can have fourteen hours of daylight in the warm months and still deliver fewer peak sun hours than a shorter winter day somewhere with clearer skies, because daylight hours count every minute the sun is above the horizon while peak sun hours only count the equivalent of full-intensity sunlight. Early morning and late afternoon light arrives at a low angle and spreads the same energy across a wider area, contributing far less per hour than the two or three hours around solar noon. This is exactly why the peak sun hours by region chart shows winter figures that fall well below what daylight length alone would suggest, and why an array sized against daylight hours instead of published peak sun hours will underperform expectations even on a clear day.

Panels sized to these numbers

Intermediate Smallest unit

Renogy

Renogy 100W N-Type Monocrystalline Panel

$102.73

The 100W building block every row in the first table below is scaled from.

Best for: Building a roof array one panel at a time.

Check price on Amazon

Beginner Portable option

BougeRV

BougeRV 200W Foldable Solar Panel

$199.99

A 200W suitcase panel you can angle toward the sun by hand, which can claw back some of the 0.75 derate that a fixed roof mount cannot.

Best for: Anyone who will actually carry the panel out each morning.

Check price on Amazon

Beginner Wiring a second panel

Link Solar

Link Solar Weatherproof Double Entry Gland

$9.89

Running a second panel's cable through the same roof entry point as the first, rather than cutting a new hole, is what a double cable gland is for.

Best for: A tidy roof entry on a flat roof.

Check price on Amazon

Frequently asked questions

How many watts of solar do I need to fully recharge a typical RV battery bank?: It depends entirely on your daily energy use and your local sun hours, not on the battery bank size alone. Add up your loads with a daily energy budget calculator to get a watt-hour target, then use the array size table above at your region's published sun hours to find the panel wattage. Two rigs with identical battery banks can need very different arrays if their daily draw differs.
Why is realistic solar output lower than the nameplate wattage?: Nameplate wattage is measured under lab standard test conditions that a roof-mounted panel almost never experiences in the field. Panel heat reduces output, a flat RV roof cannot tilt toward the sun the way a ground-mounted panel can, and wiring and charge controller conversion both lose a little more. The 0.75 derate used on this page is a commonly applied planning convention that bundles those losses into one number.
What counts as a peak sun hour?: A peak sun hour is the equivalent of one hour of sunlight at full intensity, 1,000 watts per square meter. A location's daily total is expressed as an equivalent number of these hours rather than as literal daylight hours, because real sunlight varies through the day from dawn to solar noon to dusk. It is genuinely published data per region, not a rule of thumb.
Does cloudy weather ruin solar charging?: It reduces output substantially but rarely to zero, since diffuse light still reaches the panel. The published peak sun hour figures for a region already account for typical cloud cover across a season, which is why winter figures run well below summer figures in the same location. A single unusually overcast day will underperform even the winter average.
Is 100 watts of solar per 100 amp-hours of battery a reliable rule?: It is a widely repeated planning convention and nothing more precise than that. It ignores your actual daily draw and your actual sun hours, both of which vary enormously between a weekend camper and a full-time boondocker, or between the desert Southwest and the Pacific Northwest. Use it only as a rough sanity check, and size the real array from a daily energy budget and a location's published sun hours instead.
Does 24V solar wiring change how much energy I get?: No. The array's watt-hour output depends on panel wattage, sun hours, and derate, none of which involve system voltage. What changes at 24V is the current on the battery side of the charge controller, which is half of what it would be at 12V for the same power, meaning thinner controller-to-battery cable can carry it within the same voltage drop limit.

Sun hours, not array wattage, is the number you cannot guess your way past. Look up your region's published figure, then use this page's per-100W scaling to size an array against your own daily energy budget rather than a neighbor's setup.