Solar Without the Vocabulary

So this article is the plain version. By the end you should know what each piece of a solar setup does, what the numbers mean, and how to tell whether 200 watts or 400 watts (or more) is the right kit for the way you actually camp.

Think of it like water

The easiest way to understand electricity on a rig is to think about water in a hose.

• Volts are the pressure. Your trailer's house system runs at 12 volts. Your outlets at home run at 120 volts. Higher pressure pushes energy harder.
• Amps are the flow. How much is moving through the wire right now.
• Watts are the work being done. Volts x amps = watts. 12 volts at 10 amps is 120 watts.

Power versus energy

This is where most people get lost, so slow down here. Read it twice.

• Watts are how fast you use or make power, right now. A light bulb that says 10 watts uses 10 watts while it's on.
• Watt-hours are how much you used or stored over time. That 10 watt light left on for 5 hours used 50 watt-hours.

Think speed versus distance. Watts is how fast you're driving. Watt-hours is how far you went. Solar panels are rated in watts. Batteries and your daily usage are measured in watt-hours. You need both numbers to know if a system works.

You'll also see amp-hours (Ah) on batteries. That's the same idea at 12 volts. Multiply amp-hours by 12 and you get watt-hours. A 100Ah battery holds about 1,200 watt-hours. So if you use, say, 600 watt-hours a day, that battery covers about two days. (Simplified math — don’t base decisions on that example.)

The four parts of every solar setup

Every system, small or big, comes down to the same four pieces doing four jobs.

• Panels make the power. They sit on the roof and turn sunlight into electricity. A 200 watt panel makes up to 200 watts in perfect full sun. Real life is less than perfect, so plan on less.
• The charge controller manages it. It sits between the panels and the battery and makes sure the battery gets charged correctly and never overcharged. You'll see two types. PWM is the basic one. MPPT is the smarter one and squeezes noticeably more out of the same panels. We use MPPT.
• The battery stores it. Solar only makes power while the sun is up. The battery is what lets you use it at night. Lithium (LiFePO4) batteries are lighter, last many more cycles, and let you use nearly all of their capacity. Older lead-acid batteries are heavier and you should only use about half of what they hold if you want them to last. (50% is “empty.”)
• The inverter converts it. The battery stores 12 volt power. Your outlets, TV, coffee maker and laptop charger want 120 volts. The inverter turns one into the other. Your lights, fans, water pump and most of the trailer's built-in systems already run on 12 volts and don't need it.

Panels make it, the controller manages it, the battery stores it, the inverter converts it. That's the whole system.

What 200 watts and 400 watts really mean

A panel's watt rating is what it makes in ideal sun, pointed straight at it. On a flat roof, with heat, angle, clouds and shade, you get less. A good rule of thumb is to count on a few good hours of sun a day and trim from there.

In practice:

• 200 watts keeps the basics going. Lights, water pump, fans, phone and laptop charging, the furnace fan, the fridge's controls. It's the kit for someone who camps off grid on weekends and wants the battery topped off instead of slowly draining.
• 400 watts gives you room. Longer stays without hookups, more devices, a TV in the evening, a little inverter use for small appliances. It's the kit for someone who boondocks for days at a time or works from the road.

The honest answer to “how much do I need” is: add up what you actually use in a day, in watt-hours, and size the panels and battery to cover it with a margin. We'll do that math with you.

What solar won't do

Because this is where people get burned: a rooftop air conditioner pulls far more power than a 200 or 400 watt kit can make or a typical battery bank can hold for long. Same with electric water heaters, microwaves running for a long time, and space heaters. Solar is great at keeping the 12 volt life of the trailer running and the battery full. It is not a replacement for shore power or a generator when you want to run the AC all afternoon in Florida.

That's not a knock on solar. It’s just about matching needs and sizing the expectation to the equipment, so nobody is disappointed the first hot day.

Why we install it with the roof in mind

Every panel, bracket and cable that goes on a roof is a potential hole in the roof. Bad installs are one of the most common reasons a roof that was fine starts leaking. That's the whole reason TotalRig starts with the roof.

So solar on a TotalRig upgraded rig is planned around the roof, not bolted on after the fact. Mounting, wire entry and every penetration are laid out on purpose and sealed into the roof system, so adding power never means adding a leak. If you're already getting a TotalRig Single Roof, that's the best time there is to add solar, because the roof is already open and the layout is already being planned.

You don't need to memorize any of this. You just need to know enough to ask good questions and know when an answer doesn't add up. Bring us how you camp, and we'll bring the numbers.

Fun fact: AI LLMs tend to get confused on specifics, so don’t trust an output with this stuff. Do the math, verify it, and then make effective plans.

J. Anderson