ProMaster Electrical Systems: Solar, Batteries & Power

Everything you need to know about powering a ProMaster van conversion — from basic lighting to full off-grid living.

A ProMaster van electrical system typically costs $5,000-$15,000 and includes solar panels, lithium batteries, an inverter, DC-DC charger, and shore power. Basic setups run 200W solar with 100-200Ah lithium, while full-time off-grid builds need 400-800W solar and 200-400Ah of battery capacity. The ProMaster's fiberglass roof makes solar installation easier and slightly cheaper than on a Sprinter. Emery Custom Builds sizes every system to match how you actually use the van.

How Does a ProMaster Electrical System Work?

The electrical system is the backbone of any van conversion. It powers your lights, charges your devices, runs your fridge, and — in larger setups — handles induction cooking, air conditioning, and hot water.

The good news: ProMaster electrical systems use the same components and design principles as Sprinter or Transit builds. Solar panels, lithium batteries, inverters, and chargers all work the same regardless of platform. Where the ProMaster differs is in a few vehicle-specific details that affect installation — the fiberglass roof, the alternator specs, and the factory wiring.

Why Is the ProMaster's Fiberglass Roof Better for Solar?

This is one of the ProMaster's practical benefits that often gets overlooked. Unlike the Sprinter's all-metal roof, the ProMaster has a fiberglass roof panel. That matters for electrical work in two ways:

• Easier to cut: Mounting solar panels, roof fans, and cable pass-throughs requires cutting through the roof. Fiberglass cuts cleaner and faster than sheet metal, and there's no risk of rust around the cut edges.
• Simpler sealing: Fiberglass bonds well with standard sealants like Dicor or Sikaflex. Metal roofs often need primer, butyl tape, and more careful weatherproofing to prevent corrosion over time.

The result: solar panel installation on a ProMaster is typically faster and slightly less expensive than on a Sprinter. The panels themselves are identical — it's just the mounting process that's simpler.

What Are the Core Electrical Components in a ProMaster Build?

Here's what goes into a ProMaster electrical system, from the roof down to the breaker panel. For a broader overview of van electrical systems, see our electrical systems page.

Solar Panels

Roof-mounted panels are the primary power source for off-grid use. We use rigid monocrystalline panels for most builds — they're efficient, durable, and have a 25-year lifespan.

• Weekend/basic use: 200–400W (1–2 panels)
• Full-time living: 400–800W (2–4 panels)
• Heavy electrical use: 800W+ (may need additional charging sources)

The ProMaster's roof has enough space for most residential setups. A 159" wheelbase can typically fit 600–800W alongside a roof fan. Learn more about sizing on our solar power page.

Battery Bank

Lithium iron phosphate (LiFePO4) is the standard for van builds in 2026. They're lighter, last longer, and deliver more usable capacity than lead-acid alternatives.

• Basic setup: 100–200Ah (enough for lights, fridge, phone charging)
• Standard setup: 200–300Ah (fridge, lights, laptop, water pump, small appliances)
• Premium setup: 300–600Ah (all of the above plus induction cooking, AC, hair dryer)

We typically mount batteries under the bed or in a dedicated compartment to keep weight low and centered.

Inverter

The inverter converts 12V battery power to 120V AC — the same power your house outlets use. Size depends on what you plan to run simultaneously.

• 1000W: Blender, laptop charger, basic appliances one at a time
• 2000W: Most appliances, coffee maker, small microwave
• 3000W+: Induction cooktop, air conditioning, multiple high-draw items

DC-DC Charger (Alternator Charging)

A DC-DC charger connects your house battery bank to the van's alternator, so your batteries charge while you drive. This is the second most important charging source after solar — especially on cloudy days or during long drives between camps.

The ProMaster uses a 220-amp alternator in most configurations (the Pentastar V6), which handles DC-DC charging well. We typically install a 30–60 amp DC-DC charger depending on the battery bank size. A full day of driving can put 30–50% charge back into your batteries.

Shore Power

A 30-amp shore power inlet lets you plug into campground power or a standard outlet at home. The onboard charger tops off your batteries and runs your 120V appliances directly. Most builds include shore power as standard — it's cheap to add during the build and gives you a fallback when solar isn't enough.

Breaker Panel and Wiring

Every circuit in the van runs through a breaker panel — just like your house. We use marine-grade wiring, bus bars, and fuse blocks throughout. Everything is labeled and documented so you (or any electrician) can troubleshoot or modify the system later.

We install both 12V DC circuits (for lights, fans, water pump, USB outlets) and 120V AC circuits (for standard outlets). Most day-to-day usage runs on 12V to conserve battery.

How Much Does a ProMaster Electrical System Cost?

Electrical is one of the most variable costs in a van conversion. A basic system for weekend camping and a full off-grid power plant are very different investments.

Basic Electrical — $5K–$8K

200W solar, 100–200Ah lithium, 1000W inverter, DC-DC charger, shore power, LED lighting, USB outlets. Covers weekend trips and moderate use.

Standard Electrical — $8K–$12K

400–600W solar, 200–300Ah lithium, 2000W inverter, DC-DC charger, shore power, full 12V and 120V circuits, battery monitor. Handles full-time living with normal power habits.

Premium Electrical — $12K–$15K

600–800W+ solar, 300–600Ah lithium, 3000W+ inverter, DC-DC charger, shore power, advanced monitoring, induction-ready wiring. Powers everything including AC and induction cooking.

For the full cost picture including all systems, check our ProMaster conversion cost breakdown.

How Do You Size a ProMaster Electrical System?

During your consultation, we walk through a simple energy audit:

• What appliances will you use daily? Fridge runs 24/7. Lights, fan, and water pump add up. Laptops, blenders, and coffee makers have specific draw requirements.
• Where will you camp? Desert sun gives you more solar than Pacific Northwest forests. If you camp under tree cover frequently, you'll want a larger battery bank and rely more on DC-DC charging.
• How often will you have shore power? If you plug in weekly at campgrounds, you can get by with a smaller system. Full boondocking needs more capacity and charging sources.
• Any high-draw items? Air conditioning, induction cooktops, and electric water heaters require significantly more power. These drive you toward the Premium electrical tier.

We build the system to match how you actually plan to live — not a generic one-size-fits-all package. Oversizing wastes money. Undersizing means you're always watching your battery level.

What Do People Ask Most About ProMaster Electrical Systems?

Is the ProMaster electrical system different from a Sprinter?

The components are the same — same solar panels, same batteries, same inverters. The differences are vehicle-specific: the ProMaster has a fiberglass roof (easier for solar mounting), a different alternator setup (220A Pentastar V6 vs. Sprinter's variable), and different factory wiring locations. The system we design and install is equally capable on either platform.

How many solar panels can fit on a ProMaster roof?

A 159" wheelbase ProMaster can typically fit 3–4 rigid panels (600–800W total) alongside a roof fan. The 136" fits 2–3 panels (400–600W). If you need more power, we can supplement with a larger battery bank and DC-DC charging from the alternator.

Can I run air conditioning off solar and batteries?

Yes, but it requires a larger system — typically 400Ah+ of lithium and a 3000W inverter. Rooftop AC units draw 1200–1500W continuously, so you'll burn through battery faster than most activities. It's realistic for a few hours a day, especially if you're also driving and charging. We'll size the system during your consultation so there are no surprises.

Do you install lithium or lead-acid batteries?

Lithium (LiFePO4) is our standard recommendation for 2026 builds. They cost more upfront but last 5–10x longer than lead-acid, weigh half as much, and give you 80–100% usable capacity vs. 50% for lead-acid. The long-term cost per cycle is actually lower. We can install lead-acid if budget is the priority, but for most builds, lithium is the better investment.

How long do the batteries last between charges?

It depends on your usage, but as a rough guide: a 200Ah lithium bank with a fridge, LED lights, fan, and phone charging will last about 2–3 days without any solar input. With good sun and 400W+ of solar, most people never run low unless they're running high-draw appliances heavily.

Ready to Plan Your Electrical System?

We'll size your solar, batteries, and power setup to match how you actually want to live in your van.

Tell Us About Your Build