RV Solar Panel Wattage Calculator

Enter your daily energy needs and sun hours — see exactly how many panels you need in every standard wattage.

Your RV energy needs

Daily energy usage?

Wh/day

Peak sun hours?

hrs/day

System efficiency?

Total solar watts needed

625 W

Panel count by wattage

Panel size	Qty	Total W	Excess	Roof sq ft
100W	7	700	+12%	~70 sq ft
175W	4	700	+12%	~70 sq ft
200W	4	800	+28%	~80 sq ft
300W	3	900	+44%	~153 sq ft
400W	2	800	+28%	~136 sq ft
500W	2	1,000	+60%	~170 sq ft

Charge controller (12V)66A MPPT

Battery (AGM, 3 days)1,250 Ah

Battery (Lithium, 3 days)782 Ah

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How to Use This Calculator

Enter your daily Wh usage

The daily energy usage in watt-hours is the only number that actually matters for sizing your solar array. If you don't know yours, use the RV Solar Calculator to add up your appliances. General benchmarks: minimalist van life (400-800 Wh), weekend camping (1,000-1,500 Wh), full-time with work (2,000-3,000 Wh), with rooftop AC (4,000-6,000 Wh).

Set peak sun hours

Peak sun hours for your typical travel area directly determines how much your panels produce each day. A 400W array in Phoenix (6.5 PSH) produces 2,080 Wh/day. The same array in Seattle (3.5 PSH) produces only 1,120 Wh/day. If you travel across multiple climates, use an average — 5 hours is reasonable for most of the continental US.

Compare the panel count table

The output table shows exactly how many panels you need in each popular wattage (100W through 500W), the actual total watts (rounded up to whole panels), the excess capacity percentage, and the estimated roof space needed. Use this to match your available roof to the best panel size.

The Formula

Solar Watts needed = Daily Wh ÷ Peak Sun Hours ÷ System Efficiency Panel count = Solar Watts ÷ Panel Wattage (round up) Total array Watts = Panel count × Panel Wattage Excess capacity = (Total Watts − Needed Watts) ÷ Needed Watts × 100%

System efficiency of 0.80 (80%) is the standard for RV systems with an MPPT charge controller. It accounts for: MPPT conversion losses (~5%), wiring resistance (~2%), temperature derating (~5-10% on hot metal roofs), and soiling. A basic PWM controller drops efficiency to ~0.75. High-efficiency setups with properly sized wiring in cooler climates can achieve 0.85+.

Example

Chris — Full-timer with work setup, road-tripping nationally

Chris uses 2,500 Wh/day (laptop, fridge, fan, lights, occasional microwave via inverter). They travel nationally, so 5.0 peak sun hours is a good average.

Daily usage2,500 Wh/day

Peak sun hours5.0 hrs/day

System efficiency80%

Watts needed625W

Panel count options

7 × 100W = 700W~70 sq ft roof

4 × 200W = 800W~80 sq ft roof

3 × 300W = 900W~153 sq ft roof

2 × 400W = 800W~136 sq ft roof

For a Sprinter with ~80 sq ft of roof, four 200W panels is the cleanest fit — exactly 800W fits comfortably. If they upgrade to a Class C RV with more roof, two 400W panels or three 300W panels give the same power in fewer mounting points. The 200W or 400W option both work; 400W panels use less roof space and have fewer wiring connections.

FAQ

How many watts of solar panels do I need for an RV? ▼

Common RV solar system sizes by use case: 200W (minimal weekend use), 400W (weekend with fridge and fan), 600-800W (full-timer without AC), 1,000-1,500W (full-timer with occasional AC), 2,000W+ (running AC regularly). The most accurate answer comes from your actual daily Wh usage — enter it above and see exactly what you need.

Is 400W of solar enough for full-time RV living? ▼

400W produces 1,600-2,600 Wh/day (at 5 peak sun hours, 80% efficiency). That covers a full-timer with careful usage: 12V fridge, fan, laptop, lights, and phone charging. It does not cover AC. If you have a CPAP, heavy laptop use, or a larger fridge, 600W is a safer starting point. Many full-timers find 400W insufficient and wish they had started with 600-800W.

Should I get 200W panels or 100W panels for my RV? ▼

200W panels are generally the better choice for most RVs — lower cost per watt, fewer wiring connections, and similar roof space efficiency compared to 100W. 100W panels are practical when you need flexibility (mounting at different angles) or have limited roof sections. The 400W and 500W large-format panels are gaining popularity for Class A and Class C RVs with larger flat roofs — fewer panels, fewer connections, cleaner wiring.

Does shading affect how many solar panels I need? ▼

Yes — shading is the #1 real-world performance killer. If your RV roof has vents, AC units, or antenna masts casting shadows, or if you camp under trees, your effective production can drop 20-50%. Solutions: (1) Add 20-30% extra capacity to compensate. (2) Use panels wired in parallel so a shaded panel doesn't kill the others. (3) Use individual panel optimizers if wiring in series (for MPPT efficiency). Most RV parks face east-west parking — morning and afternoon shade are common and unavoidable.

Can I mix solar panels of different wattages on the same RV? ▼

You can mix panels if wired in parallel (each panel connects directly to the charge controller). In a parallel configuration, different wattages and even different voltages (as long as Voc is within controller spec) work without major issues — the weaker panel doesn't drag down the others. Avoid mixing panels in series with different Voc/Isc ratings, as this reduces total output. Most RV installs use parallel wiring for simplicity and partial-shade tolerance.