How to Size Your travel trailer Power System (Without Getting It Wrong)

The Problem With Guessing

Most people set up their travel trailer power system by asking a mate, reading a forum post from 2019, or just buying whatever the shop assistant recommends. The result? Either a system that costs twice what it should, or one that leaves you in the dark by 9pm.

The good news is that sizing a power system isn't complicated. You just need to know three things:

1. How much power you actually use each day
2. How you'll recharge (solar, driving, generator)
3. How long you want to stay off-grid without plugging in

Once you know those numbers, everything else falls into place.

Step 1: Work Out Your Daily Power Usage

Every appliance in your travel trailer draws a certain number of watts. Multiply watts by hours of use per day, and you get watt-hours (Wh) — your daily energy consumption.

Here are some common appliances:

Typical daily usage: 1,200–2,000 Wh for a couple traveling with a fridge, lights, fans, and devices.

Don't guess — add up your actual appliances. We built a free Power System Planner that does this calculation for you. Just tap your appliances and it works out the rest.

Try the Power System Planner →

Step 2: Choose Your Battery

Your battery stores the energy you use overnight and between charges. The three main types are:

Lithium (LiFePO4) — The Clear Winner

• 80% usable capacity (a 200Ah battery gives you 160Ah)
• 3,000+ charge cycles (lasts 8–15 years)
• Lightweight — about 22kg for 200Ah
• Fast charging — fully charged in 2–4 hours
• Cost: ~$4.50/Ah ($900 for 200Ah)

AGM — The Budget Option

• 50% usable capacity (a 200Ah battery only gives you 100Ah)
• 500 charge cycles (lasts 3–5 years)
• Heavy — about 60kg for 200Ah
• Slow charging — 6–10 hours
• Cost: ~$2.00/Ah ($400 for 200Ah)

The Maths

Lithium costs more upfront but is cheaper per cycle. A $900 lithium battery lasting 3,000 cycles costs $0.30 per use. A $400 AGM lasting 500 cycles costs $0.80 per use.

For most travel trailer setups, 200Ah of lithium is the sweet spot. It gives you 160Ah of usable power — enough for 1–2 days of typical use without any charging.

Read the Battery Buying Guide →

Step 3: Set Up Your Charging

Your battery is only as good as your ability to recharge it. Most setups use a combination of these:

Solar Panels

The most popular off-grid charging source. A 200W panel with 5 hours of sun produces about 800Wh per day (after efficiency losses). That covers a basic setup but may fall short in cloudy weather or winter.

Tip: Always oversize your solar. A 400W setup gives you a buffer for bad weather.

DC-DC Charger

Charges your house battery from your vehicle alternator while driving. A 30A DC-DC charger driving for 3 hours puts about 970Wh into your battery. Essential if you're touring (driving most days) rather than sitting at one campsite.

Popular brands: REDARC, Enerdrive, Renogy

Generator

A backup option for extended cloudy periods. Most people don't want to rely on one, but a small 2kW generator can fully recharge a 200Ah battery in a few hours.

Shore Power

If you stay at powered travel trailer parks sometimes, your onboard charger will top up the batteries overnight. This resets your off-grid clock.

Step 4: Do You Need an Inverter?

An inverter converts your 12V battery power to 240V mains power. You need one if you want to run:

• Microwave
• Hair dryer
• Electric kettle
• Coffee machine
• Any appliance with a regular power plug

Pure sine wave inverters are recommended — they're safe for all electronics. Modified sine wave inverters are cheaper but can damage sensitive equipment.

Sizing: Your inverter needs to handle the highest single load. If your microwave draws 1,000W, you need at least a 1,500W inverter (to handle the startup surge).

Putting It All Together

Here's a typical setup for a couple doing a mix of free camping and travel trailer parks:

This setup gives you:

• Indefinite off-grid in good weather (solar covers daily usage)
• 2–3 days in cloudy weather before needing to drive or plug in
• 240V power for a microwave, kettle, and laptops

Use the Free Power System Planner

Rather than doing all this maths by hand, use our Power System Planner. It walks you through:

1. Listing your appliances (with common presets)
2. Setting your off-grid target (how many days)
3. Configuring your charging (solar, DC-DC, generator, inverter)
4. Getting battery recommendations (size, type, cost)
5. Seeing your full system summary (with a shopping list)

It's free to use — no signup required for the first three steps.

Plan Your Power System Now →

Useful Resources

• Clean Energy Council — Solar Panel Standards
• Battery University — Lithium vs Lead-Acid
• REDARC — 12V System Guides

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KamperHub Team

Helping travellers tow safely and confidently. KamperHub provides tools for trip planning, weight compliance, and adventure management.