Teardrop Trailer Solar Calculator
Size your boondocking system by roof space, days off-grid, and CPAP needs — in 3 minutes.
Start Calculator ↓Build Your System
Answer five questions about your trailer, your appliances, and your boondocking style. We'll size the panel, battery, and inverter for you — including CPAP if you run one.
What's your trailer size?
This sets your available roof space for solar.
Select a model to see how many panels fit.
Classic small
Medium teardrop
Large / T@B style
Custom / off-road
How will you mount your panels?
Portable panels remove the roof-size cap entirely.
Roof mount only
Portable ground deploy
Roof + portable hybrid
What's your boondocking style?
This sets how much battery buffer you'll want.
Weekend warrior
Long weekend (4-5 days)
Extended (7+ days)
What are you running?
Check everything you'll actually use. We'll total the daily draw live.
Essential
Very common
Medical / special
Extras
Where do you usually camp?
This sets your effective sun hours per day.
Summer Southwest
Spring/Fall anywhere
Shaded campsite
Winter camping
Your Recommended System
Why Teardrops Are Different
Most RV solar guides are written for Class A motorhomes with 200 square feet of roof and a chassis that shrugs off an extra 300 pounds of battery. None of that applies to a teardrop. You're working with a roof the size of a card table, a tow vehicle with a real payload limit, and a trailer that was never designed with solar in mind.
That changes every decision. Roof space, not budget, is usually the ceiling on how much power you can generate. Weight, not cost, is usually the deciding factor between AGM and lithium. And boondocking style — a weekend at a music festival versus seven days on BLM land — changes your battery math more than it does on a bigger rig where you'd just oversize everything and move on.
This calculator sizes around those three constraints specifically: what actually fits on a small curved roof, what a CPAP machine really costs you overnight, and what to do when your campsite is shaded and your roof panel is doing nothing. Answer the five steps above and you'll get a system sized for a teardrop, not a downsized version of a motorhome calculator.
Teardrop Roof Solar Limits — What Actually Fits
Roof space is the first wall you hit with teardrop solar, and it's a hard one. A 4x8 roof has about 24 usable square feet once you account for vents, roof rails, and edge clearance — that's one 200W rigid panel and nothing more. Bolt on a second panel and you'll be drilling into curved fiberglass with nowhere flat to mount it.
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| Trailer model | Roof length | Roof width | Max rigid panel | Max flex panel |
|---|---|---|---|---|
| Classic 4x8 | 8 ft | 4 ft | 1x 200W | 1x 200W |
| 5x10 teardrop | 10 ft | 5 ft | 1x 300W or 2x 150W | 2x 200W |
| T@B 320 / nuCamp | 12 ft | 7 ft | 2x 200W | 3x 200W |
| Off-road build with rack | Varies | Varies | Up to 400W | 400W+ |
Rigid panels cost less per watt and last longer, but they're flat and heavy, and a curved teardrop roof forces gaps at the edges where nothing mounts. Flexible panels bend with the roofline, weigh a third as much, and often let you claim square footage a rigid panel would waste — the tradeoff is a shorter lifespan and a higher price per watt. If your roof is genuinely flat and rectangular, go rigid. If it curves at all, flexible earns its premium.
CPAP on Solar in a Teardrop: The Complete Guide
CPAP is the single question that changes a teardrop solar build more than anything else, because it runs every night, all night, with zero flexibility. You have two real ways to power one off-grid, and they land in very different places on cost and battery draw.
The DC travel adapter route. Machines like the ResMed AirMini or Philips DreamStation Go accept a DC adapter that plugs straight into a 12V outlet — no inverter, no conversion loss. That adapter runs $30-$50 and draws just 30-50Wh a night. If your machine supports it, this is the cheapest and most efficient path by a wide margin.
The inverter route. Standard CPAP machines need a proper AC inverter, and it has to be pure sine wave — a modified sine wave inverter can damage the CPAP's internal motor and will void the machine's warranty. A pure sine inverter runs $80-$150 and the machine itself draws 200-450Wh a night depending on humidifier use.
The humidifier is the real lever. Turning it off saves 250Wh a night — roughly one extra full day of battery life on a typical teardrop setup. If you're chasing extra boondocking days over comfort, that's the first thing to cut, not your fridge or your lights.
The Shade Problem: Why Roof Solar Fails at Wooded Campsites
A roof panel needs direct sun, and tree cover is the fastest way to lose it. Partial shade on even one corner of a panel can cut total output by 30-60%, because most panels wire their cells in series — one shaded cell throttles the whole string, not just its own square inch.
The fix isn't a bigger roof array — it's a second, independent one. A portable ground panel set up 20-30 feet away in a sunbeam keeps generating at full output while the trailer itself stays parked in the shade you picked your campsite for in the first place. It's the single highest-leverage upgrade for anyone who camps in forested BLM or national forest sites rather than open desert.
DC-DC Charger: The Secret Weapon for Teardrop Boondocking
A DC-DC charger wires into your tow vehicle's electrical system and tops off the trailer battery from the alternator while you drive — adding roughly 20-40Ah per hour on the road, depending on the charger and your battery's state of charge. Drive four hours to a remote site and you can arrive with a battery that's already most of the way full, before the solar panel has done anything at all.
This pairs especially well with a DC compressor fridge, since the fridge draws steadily around the clock and the drive-time charge covers most of that load before you've even leveled the trailer. For anyone doing multi-stop trips with driving days between camps, a DC-DC charger does more for real-world battery life than an extra 100W of roof panel.
AGM vs LiFePO4 for Teardrops: Weight Matters Here
On a 10,000-lb motorhome, an extra 40 pounds of battery is a rounding error. On a teardrop with a 300-500 lb tongue weight budget and a small tow vehicle, it's not.
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| Battery | 100Ah weight | Usable Ah | Cost |
|---|---|---|---|
| AGM | 63 lbs | 50Ah (50%) | $150 |
| LiFePO4 | 26 lbs | 100Ah (100%) | $250 |
AGM batteries shouldn't be discharged past 50% without shortening their lifespan, so a "100Ah" AGM really gives you 50Ah of usable power at more than double the weight of a lithium battery that gives you the full 100Ah. For a teardrop, that's the difference between staying comfortably under your tow vehicle's payload rating and creeping toward it. The extra $100 upfront for LiFePO4 buys back both weight and capacity — for a small trailer, that trade is worth it almost every time. See our full battery guide for chemistry details and charging specs.
5 Mistakes Teardrop Owners Make With Solar
Oversizing roof panels beyond what fits
Ordering a 300W panel for a 24 sq ft roof means it never gets mounted. Measure your actual usable roof space before you buy anything.
Using a modified-sine inverter with a CPAP
It's cheaper on the shelf and it can damage the machine's motor while voiding your warranty. Pure sine only, no exceptions.
Ignoring shade at wooded sites
A gorgeous, shaded campsite is exactly where a roof-only system underperforms. Plan for a portable panel if you camp in forest, not desert.
Choosing AGM for a weight-sensitive build
Half the usable capacity at more than double the weight. On a small trailer, that math rarely works in AGM's favor.
Not considering DC-DC charging on driving days
If your trip involves multiple travel days between camps, skipping a DC-DC charger leaves free battery capacity on the table.
Frequently Asked Questions
Most teardrops need 200-400W total. A classic 4x8 roof tops out at one 200W rigid panel. A 5x10 teardrop fits 300W. Add a portable ground panel if your appliance load runs past what the roof can hold.
Yes. A DC travel CPAP adapter uses 30-50Wh/night with no inverter needed. A standard CPAP through a pure sine inverter uses 200Wh/night without a humidifier, or 450Wh/night with one running.
A classic 4x8 roof fits one 200W rigid panel. A 5x10 teardrop fits one 300W panel or two 150W panels. A T@B 320 or nuCamp-style roof fits two 200W panels. Flexible panels handle curved roofs better and often allow more surface coverage.
For a typical load of 400-600Wh/day, budget for 100-150Ah of LiFePO4 to cover 5 days without full sun every day. Add capacity if you're running a CPAP with a humidifier.
Rigid panels are cheaper per watt and last longer. Flexible panels weigh less, sit lower for better aerodynamics, and follow curved teardrop roofs, which often means more usable wattage on a small roof.
Tree cover cuts roof solar output by 30-60%. Deploy a portable ground panel in a nearby sunny spot instead of relying on the shaded roof, and run a longer cable back to the trailer.
LiFePO4 is worth the extra cost for a teardrop. A 100Ah AGM weighs about 63 lbs and only gives you 50Ah usable. A 100Ah LiFePO4 weighs about 26 lbs and gives you the full 100Ah, which matters on a trailer with a tight tongue-weight margin.
Yes. A DC-DC charger pulls power from your tow vehicle's alternator while driving, adding roughly 20-40Ah per hour on the road, so you can arrive at camp with a full battery even before the solar panel does any work.