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Solar planner

Plan your RV solar, starting with the roof

Pick your rig, measure the roof, check off what you run. You'll see the panels laid out around your A/C units, then three ways to build it with a parts list for each.

By James JonesUpdated

Load table, battery logic, and solar math from the original megawattrv.com calculators

Solar panels mounted on the white roof of a motorhome parked in the desert at golden hour
Illustration generated for Megawatt RV.

01 Your rig

Rig type

02 Your roof

Starting numbers change with the rig type. Measure yours with a tape; the flat part is usually shorter than the coach.

ft
ft
Air conditioners
Vents and fans
Panel size: 200 W, 58 × 26 in
W
in
in

A planning footprint. Check the spec sheet of the panel you buy.

03 What you run

The checklist is the Megawatt load table for your rig size.

Add your own

04 How you travel

Most nights you're
Plan for the sun in

Without a ZIP, the planner uses the original Megawatt presets: 3, 4, and 5.5 sun hours.

ft

One way. Longer runs need thicker cable.

Your roof

  • Panel
  • A/C unit
  • Vent or fan

Daily energy budget

0Wh a day

    Your plan

    Three ways to build it

    Each build sizes the battery, inverter, controller, and cable to your loads. Parts link to Amazon; the cart shows today's total.

    Rather not drill the roof yourself?

    Get matched with an installer

    We'll show you the solar installers and certified pros listed in public directories near your ZIP, and pass your plan to James. Megawatt's own partner network is coming soon.

    Get matched with an installer

    How the planner does the math

    Daily budget. Checked loads use the watt-hours from the original Megawatt table. Your own loads are watts × hours.

    Roof. Panels sit 6 inches in from each edge with an inch between them, and 3 inches clear of each A/C unit and vent. The planner tries both panel orientations and keeps the one that fits more. A/C units are sketched at 40 × 30 inches and vents at 22 × 22, spaced evenly. Your roof won't match exactly, so measure before you buy.

    Array. Daily watt-hours ÷ (sun hours × 0.75), the original Megawatt formula. Weekend covers half of that from the roof, Boondocker covers all of it, and Off-grid adds 15% for gray days. Those coverage levels are planning choices, not measurements.

    Battery. Each build holds a set number of days of use with no sun at all: one and a half for Weekend, two for Boondocker, three for Off-grid. That reserve is what gets you through a storm. Voltage follows the original Megawatt rule (24 V above 3,000 W of peak draw, 48 V above 5,000 W) and also steps up when a 12 V bank would pass 8 kWh or a 24 V bank would pass 16 kWh, so you are not wiring a wall of parallel batteries.

    Inverter and controller. Both get a 25% cushion. The inverter rounds up to the next 1,000 W. The controller rounds up to a stock size and splits into two above 100 A.

    Cable and fuse. The Megawatt wire table at 3% drop, from the controller run you set and a 6-foot inverter run. The main fuse is sized to that inverter cable.

    Before anything gets connected, have a qualified electrician review the plan.