Before you buy batteries or solar panels, you need to figure out how much power you'll actually use each day. This page covers the key concepts, then use our Electrical Capacity Planner to calculate your specific setup.
Electrical components have gotten dramatically cheaper in recent years, but running out of power is still extremely stressful and disruptive. The extra $100-200 for a larger battery or an additional solar panel is almost always worth it.
Running low on power when you're relying on it to do your remote work, keep your food from spoiling, run your heater in freezing weather, or charge essential devices is not just inconvenient - it can derail your entire trip or work schedule. When in doubt, size up.
Your power strategy depends entirely on your use case:
Think of it this way:
If you're weekend camping, you're living off your battery (like a gas tank). If you're full-timing, you're living off your solar/alternator generation (like MPG), and your battery is just your reserve tank.
Every van setup is different. Rather than guessing from static tables, use our interactive planner to select your actual devices, adjust for your season, and get personalized battery and solar recommendations.
Select your devices (fridge, laptop, heater, AC, etc.), configure your solar and DC-DC charger, and see exactly how much battery capacity you need - with seasonal adjustments and generation vs. consumption breakdowns.
Open the Planner →Solar panels are rated at their peak output under ideal conditions. In the real world, you get much less. Understanding this gap is critical for sizing your system correctly.
A 200W panel only produces 200 watts under perfect conditions: bright midday sun, panel perpendicular to the sun, cool temperatures, clean panels, zero shade.
In practice, expect 50-70% of rated capacity averaged throughout the day.
Fixed mounting angle: Your panels are flat on the roof and only perpendicular to the sun briefly each day (if ever). Sun angle alone can cut output by 25-50%, especially in winter.
Heat: Panels lose ~0.5% efficiency per degree C above 25°C. On a hot day with roof panels at 60°C, you're losing 15-20% from heat alone.
Dirt and partial shading: Dust, pollen, bird droppings, and shadows from roof vents or tree branches can reduce output by 10-20%.
Portable panels are valuable:
If you can angle panels toward the sun, you get significantly better output. Some people use portable panels specifically for winter or extended stationary camping.
Here's what 400W of roof-mounted solar panels realistically produces. Our Electrical Capacity Planner uses these same seasonal factors.
~1,560 Wh/day
5-7 peak sun hours × 60-70% efficiency. Long days help, but heat reduces efficiency.
~1,400 Wh/day
4-6 peak sun hours × 65-75% efficiency. Often the best actual production due to cooler panel temps.
~780 Wh/day
2-4 peak sun hours × 60-70% efficiency. Short days and low sun angle are the killer. More cloudy days too.
150-400 Wh/day
10-25% of rated capacity. You're running a deficit - this is why battery buffer and DC-DC charging matter.
Often overlooked but can be a game-changer, especially in winter. A DC-DC charger takes power from your vehicle's alternator and safely charges your house battery while you drive.
If you drive 1-3 hours between spots, this generates serious power.
When solar is weak, many people rely on alternator charging. Drive to a new location, charge batteries, camp for a day or two, repeat.
A 60A DC-DC charger fully charges a 280Ah battery in ~5 hours of driving; the smaller 40A unit takes about 7 hours.
The trade-off: You need to be driving. If you want to sit in one spot for a week, alternator charging doesn't help. For stationary camping, solar is your primary source.
Winter caveat: LiFePO4 won't accept charge below 32°F / 0°C — the BMS refuses current to protect the cells. If you'll camp in sub-freezing temps, get a self-heating pack (LiTime, Battle Born GC3 Heated) or add a silicone heat pad before relying on driving-and-charging as your winter strategy. The batteries guide covers cold-temp behavior in detail.
If you're a weekend warrior: Think of your battery like a gas tank. Size it big enough to hold all the power you need for a weekend, and don't worry too much about solar - you'll refill at home. A 280Ah battery with 200-400W of solar works great.
If you're full-timing or taking extended trips: Think of your solar and DC-DC charging like your MPG - they determine how much power you can use sustainably. Your battery is just your reserve tank for cloudy days. You need 600-800W+ of solar and a 40A DC-DC charger (or 60A if your alternator can support it) to match a 1,500 Wh/day lifestyle.
I see people install a huge 600Ah battery with only 400W of solar for full-time living, then wonder why they're constantly running low. The battery doesn't solve the problem - it just delays it by a day or two.
Components are cheap now. Lithium battery prices have dropped substantially over the past several years. An extra 100Ah costs $150-250.
Running low is stressful. Watching your battery percentage drop when your work, food, or heat depends on it is not worth saving $200.
Power needs creep up. You'll find more uses for power once you have it. Plan for this.
Worst-case weather happens. A week of clouds, a brutal cold snap, a heat wave - an undersized system becomes a liability.
If you're running low, you can always eat cold meals, use devices less, drive somewhere to charge, or find shore power. But you don't want to do this regularly. Your system should support your normal lifestyle comfortably.
It's far better to have more capacity than you need than to constantly worry about running out.
Once you've figured out your power needs with the planner, here's what I recommend. These Vevor components are a fraction of the price of the popular brands (Victron, Renogy, Battle Born) and work just as well in my experience.
I run a Vevor 60A DC-DC paired with separate MPPT controllers for the solar side. The 60A sits comfortably on my upgraded alternator and tops up a 280Ah bank in about 5 hours of driving. If you haven't upgraded the alternator, the Vevor 40A is the better default — at ~$104 it stays inside the 30-50% window on a stock 130A alternator and is half the price of a Victron Orion 30A.
This is your insurance policy for cloudy days and winter camping. Non-negotiable for extended trips. See the DC-DC chargers guide for full sizing math, the 30-50% alternator rule, and dual-alternator setups.
You need an MPPT controller (not PWM) to get the most out of your solar panels. MPPT controllers are 20-30% more efficient than PWM, which adds up to real power over a full day. The Vevor 50A MPPT is a great value.
Size your controller to handle your total solar wattage. A 50A controller handles up to ~800W of panels at 12V. See the charge controllers guide for the cold-temperature Voc cap (Vevor 50A maxes at 100V PV input) and when to run two 50A units instead of one bigger controller.
Link to our favorite charge controller →Get a pure sine wave inverter - modified sine wave can damage sensitive electronics. The Vevor 3000W is what I run. 3000W handles anything you'll throw at it in a van, including induction cooking.
Don't go smaller than 2000W if you plan to use an induction cooktop. A single induction burner pulls 1800-2000W at full power. See the inverters guide for pure-sine vs modified-sine, BMS continuous-current sizing, and the 4/0 AWG + Class T fuse install.
Link to our favorite inverter →LiFePO4 (lithium iron phosphate) is the way to go. They're lighter, last longer (3,000+ cycles vs 500 for AGM), and can be discharged deeper without damage. Prices have dropped dramatically.
Get at least 280Ah for weekend use, 280-560Ah for extended trips, 560Ah+ for full-time with remote work. Don't regularly discharge below 20% to maximize lifespan. See the batteries guide for Eco-Worthy vs Battle Born vs Renogy at 280Ah, BMS continuous-current sizing, and cold-charge protection.
Link to our favorite battery →For roof-mounted panels, get the highest wattage that fits your roof. Most vans can fit 400-800W depending on layout and other roof equipment.
200-400W for weekend use, 600W+ for extended trips, 800W+ for full-time living. Remember: you'll get 50-70% of rated capacity in real-world conditions. See the solar panels guide for series vs parallel, the cold-temp Voc uprate, and mounting options.
A note on brands: The van life community has a strong bias toward expensive brands like Victron and Battle Born. They make great products, but you're paying 2-3x for a name. Vevor components use the same underlying technology and come with solid warranties. The money you save is better spent on more capacity.