How Many Watt-Hours Does a Van Build Actually Need? We Did the Math.

The spec sheet lies. When you look at a portable power station’s 1,024 Wh capacity, your brain pictures 24 hours of freedom. It doesn’t. We watched real van lifers stare at a 15% battery warning at 11 PM, having miscalculated their fridge draw by 200 Wh and now facing dead panels in a cloudy week. This walkthrough prevents that by running three actual appliance loads — compressor fridge, CPAP with humidifier, laptop and lights — through the math so you know exactly what size unit fits your rig.

The Real Load: Three Days Off-Grid

Most van lifers’ daily power budget breaks down like this: a quality 12V compressor fridge cycles on and off all day, a CPAP with heated humidifier runs 8 hours at night, and a laptop plus cabin lighting fills the gaps. The 72-hour window below assumes no shore power and clouds blocking solar input.

Compressor Fridge (400–600 Wh/day)

A 40L–50L Dometic CFX or ARB-series fridge pulls roughly 400 Wh per day in mild conditions (70°F ambient), and balloons to 600+ Wh on a 95°F day. The fridge doesn’t run at a constant 30W — it cycles. You’ll see 50W spikes when the compressor kicks in, then 0W during the off cycle. Over 24 hours, that averages to 16–25W continuous.

To calculate: a Dometic CFX 40L consumes about 40 Ah per day at 12V. To convert to watt-hours, multiply amp-hours by voltage: 40 Ah × 12V = 480 Wh/day. On a hot day, add 50%.

CPAP with Heated Humidifier (240–800 Wh/night)

A standard CPAP at 7–8 cm H₂O without humidification pulls 30–50W. Add a heated humidifier at pressure above 10 cm H₂O, and you’re looking at 60–100W per night. Without humidification at low pressure that’s 240–400 Wh; at pressure above 10 cm H₂O with full humidifier heat, plan for up to 800 Wh. For an 8-hour sleep window, the conservative estimate is 60W × 8 hours = 480 Wh (note: full humidifier operation at high pressure can reach 800 Wh — size accordingly).

Laptop, Lights, USB Charging (120–180 Wh/day)

A 100W laptop charger running 6 hours = 600 Wh, but most van lifers charge sparingly. Budget 2–3 hours of active laptop use per day (200–300 Wh), plus LED cabin lighting at 10W for 6 hours (60 Wh), plus phone and device trickle charging (30 Wh). Real consumption: 150–200 Wh/day.

The 72-Hour Math

Appliance	Daily Wh	3-Day Total
Compressor Fridge	450	1,350
CPAP + Humidifier (nights only, conservative)	480	1,440
Laptop + Lights + USB	180	540
Daily Total	1,110	3,330

Three days of realistic off-grid use demands 3,330 Wh burned. A single 1,000 Wh unit gets you through one day comfortably, two days if you ration aggressively (cold laptop, dim lights). A 2,000 Wh station covers 72 hours without stress. CPAP users running full humidifier heat at high pressure should add 300 Wh/night to this baseline.

But spec-sheet numbers are theoretical. Real portable power stations operate at 80–85% usable capacity due to inverter losses, internal management circuits, and the battery management system’s conservative depth-of-discharge algorithm. A 1,000 Wh EcoFlow DELTA 2 holds 1,024 Wh nameplate, but you can reliably draw about 820 Wh before the battery management system cuts off at 5% remaining charge. The math tightens fast.

When 1 kWh Is Enough (and When It Isn’t)

1,000 Wh fits if:

• You’re a weekender (3–4 nights), not a full-timer
• You have reliable solar input (200W panel, 4+ hours of direct sun daily)
• You’re willing to charge off shore power or a running engine every other day
• Your fridge is efficient and your climate is mild
• You run the laptop sparingly and lights on low

The Jackery Explorer 1000 v2 (1,070 Wh, LiFePO₄) or EcoFlow DELTA 2 (1,024 Wh, expandable) works here. The Jackery edges out the EcoFlow on cycle life (4,000 vs. 3,000 rated cycles), but the EcoFlow charges faster (1.2 hours vs. 7.5 hours on AC).

You need 2+ kWh if:

• You’re full-time or semi-full-time (30+ days per month off-grid)
• You’re two people with two CPAP machines
• Your climate forces consistent fridge cooling (desert, tropics, summer travel)
• You have a partner who works remotely (full 8 hours laptop daily)
• You don’t have predictable solar windows (cloudy weeks, winter travel)
• You want to avoid charging more than once per week

An EcoFlow DELTA 2 Max (2,048 Wh, expandable to 3 kWh) or a stacked dual Jackery 1000 v2 setup covers the 3,330 Wh three-day burn comfortably and leaves room for inefficiency, parasitic draw, and the inevitable week when you miscalculated how much the CPAP would run.

Recharge Reality: Shore, Solar, and Alternator

The spec sheet assumes a full recharge each cycle. Real van life isn’t that clean.

Shore Power (wall outlet at a campground)

If you dock once a week at a paid site, a 1,000 Wh station charges in 1.2–7.5 hours depending on the unit. EcoFlow’s X-Stream fast charging tops a DELTA 2 in 90 minutes on 240V. That’s your easiest reset, but it’s not always available.

Solar Panels (200–400W roof array)

A 200W roof-mounted panel on a clear day delivers roughly 1–1.2 kWh by sunset. Factor in panel angle losses, dust, and the fact that van roofs are rarely pointing due south, and real-world input is 60–70% of nameplate. In a cloudy week, you might only pull 300–400 Wh per day. That doesn’t sustain a 1,110 Wh/day load. You’re eating battery reserve.

Budget conservatively: if you have 200W of solar, assume you can replace 600–800 Wh per sunny day. On cloudy days, zero.

Alternator/DC-DC Charging (while driving)

While the engine runs, a quality DC-DC charger can push 20–30A into a 100 Ah lithium bank (full setup, not a portable station). That’s 240–360W — fast enough to top off a portable station in 4–6 hours of highway driving. But if you’re parked and not moving, the alternator can’t help.

For portable power stations specifically, most models accept 500W of solar input and a 12V cigarette-lighter input (typically 10A max, 120W — slow). The limitation is the station’s charging circuits, not your solar array.

The Decision: What We’d Actually Buy

If you’re buying your first van power station and expect to stay off-grid 30–60 days per year with reliable solar access, the Jackery Explorer 1000 v2 is the answer. It’s lighter than the EcoFlow, has better long-term cycle life, and at $999 MSRP, it leaves budget for a decent 200W solar array. Pair it with a Kill-A-Watt meter on your fridge to measure your actual daily draw — most van lifers are shocked to discover they’re pulling 100 Wh more than they guessed.

If you’re full-time or run two CPAP machines, or if you anticipate cloudy stretches without shore power, the EcoFlow DELTA 2 Max (2,048 Wh) eliminates the stress math. Yes, it costs more. But the cost of a dead battery at midnight in a cold week is higher.

For extreme cold-weather operation, note that LiFePO₄ chemistry performs better below freezing than older NMC cells, which is another point in favor of both the Jackery and EcoFlow options here.

The math is the map. Run it before you mount anything.