How to Size a Camp Generator for Real Loads

A dead power station at 2 a.m. changes the whole camp. The fridge warms up, the fan quits, and the portable AC becomes a very expensive box when the afternoon heat returns. Knowing how to size a camp generator starts with the equipment you will actually run, not a vague promise of “enough power.”

For a truck, SUV, or trailer basecamp, generator sizing is about building a system that can handle real routines: cold food, light after dark, device charging, ventilation, and possibly cooling. The right unit lets you leave camp standing, take the truck into town or down the trail, and return to a powered camp. The wrong unit may run a phone charger just fine, then shut down the moment a compressor starts.

How to Size a Camp Generator: Start With Watts

First, separate the two numbers that get confused most often: watts and watt-hours. Watts measure how much power an appliance needs right now. Watt-hours measure how much stored energy the generator has available over time.

A portable power station rated for 1,000 watts can supply up to 1,000 watts of AC load at one time. A station with a 1,000Wh battery can theoretically run a 100-watt load for 10 hours. In the field, plan for less than the theoretical number because inverter losses, heat, battery protection, and cycling appliances all consume some capacity.

Make a list of every device you expect to run at the same time. Use the appliance label, manual, or manufacturer specification. Do not size from a USB port count or a marketing claim alone. What matters is true AC output, battery capacity, and the unit’s surge rating.

A typical vehicle-supported camp might include a 12V compressor fridge, LED lights, phones, camera batteries, a laptop, and a fan. That is a modest load. Add an electric blanket, coffee maker, induction cooktop, microwave, or portable air conditioner, and the demand changes fast.

For a realistic starting point, a compressor fridge may average 30 to 70 watts while cycling, though it can pull more at startup. LED camp lights may use 5 to 20 watts total. A fan often falls in the 20 to 60 watt range. A laptop charger may draw 45 to 100 watts. These are manageable loads for many quality power stations.

Heating and cooling are different. An 8,000 BTU portable air conditioner can require several hundred watts while running and may need considerably more during compressor startup. Its actual draw depends on ambient temperature, hose setup, insulation, thermostat setting, and whether the tent or trailer is baking in direct sun. A thin-walled shelter with no shade asks far more of the AC than a properly shaded, closed-up basecamp.

Add Running Watts and Startup Surge

Once you have your list, add the running watts for equipment that may operate together. Then account for surge watts. Motors and compressors in fridges, pumps, and air conditioners can demand a short burst of extra power when they start. If the generator cannot handle that burst, it can trip even when the listed running load looks safe.

Here is a practical example. Say your camp runs a fridge averaging 60 watts, a fan at 40 watts, lighting at 15 watts, and charging at 85 watts. Your normal operating load is about 200 watts. Add a portable AC drawing 700 watts and you are near 900 watts before compressor surge.

A 1,000-watt power station might look adequate on paper, but it leaves almost no operating margin. A 1,500- to 2,000-watt continuous AC output is the more sensible range for that setup, provided the surge rating supports the AC compressor. More headroom means fewer nuisance shutdowns and less need to carefully sequence every appliance.

Do not assume a higher watt rating means longer runtime. A generator with 2,000 watts of inverter output and a 1,000Wh battery can run a high draw appliance, but not necessarily for long. You need enough power output and enough stored energy.

Calculate Battery Capacity for Overnight Runtime

To estimate battery capacity, multiply the appliance’s average watts by the hours you expect to use it. This gives you watt-hours.

If a 50-watt fan runs for eight hours, it needs roughly 400Wh. If your fridge averages 45 watts across a 24-hour day, it needs about 1,080Wh. Add lights, charging, and inverter losses, and a 1,500Wh battery is a more realistic minimum for one day of fridge-and-fan duty than a small 500Wh unit.

Use this formula:

Average watts × hours used = watt-hours needed

Then add a margin of at least 20 to 30 percent. Camps rarely follow a perfect spreadsheet. A hot day makes the fridge cycle more often. A kid leaves a light on. You arrive late with battery-powered tools, camera gear, or a laptop that needs charging.

For a simple weekend camp without air conditioning, 1,000 to 1,500Wh can cover a well-managed load of refrigeration, lights, fans, and devices. For several days away from hookups, 2,000Wh or more provides a more useful buffer, especially for families or trailer camps with more than one sleeping area.

Portable AC changes the math. A 700-watt air conditioner running for four hours consumes around 2,800Wh before losses. It may not run continuously, but assuming it will barely cycle is a bad plan during a humid summer night. If cooling is non-negotiable, size the battery system around the AC first, then add the rest of camp.

Match Recharge to Your Camp Schedule

Battery capacity only gets you through the first cycle. For extended stays, your recharge plan matters just as much as the generator itself.

Solar is quiet and useful when camp stays put. It works best when panel wattage is sized to restore a meaningful part of the previous day’s use during available sun. A 200-watt panel does not deliver 200 watts all day. Angle, shadows, cloud cover, panel temperature, and charge-controller limits reduce real production. Treat its rated wattage as a best-case ceiling, not a daily guarantee.

For a 1,500Wh power station powering a fridge, lights, and charging, 200 to 400 watts of solar can be a practical starting range depending on location and season. If your daily use is closer to 2,000Wh, a single small panel will not keep up reliably. You need more panel area, vehicle charging while driving, a fuel generator, or lower consumption.

Vehicle charging is valuable for mobile campers because the truck is already moving. But check the charging rate. A slow 12V outlet may add only a modest amount over a long drive. Higher-output DC charging can make a real difference when traveling between trailheads or resupply stops.

A conventional fuel generator remains useful when weather is poor, shade is unavoidable, or AC loads are heavy. It brings noise, fuel storage, and campground restrictions, so it is often best used as a recharge tool rather than something running beside the tent all night. Run it during permitted hours, recharge the battery station, then switch back to quiet stored power after dark.

Build for the Loads You Will Actually Use

The cheapest way to oversize a camp generator is to reduce unnecessary demand. Shade from an awning lowers the cooling burden before the AC starts. A trailer tent with durable fabric, proper ventilation, and a controlled sleeping area is easier to cool than an oversized shelter with open doors and sun beating through thin material. Pre-chill the fridge before departure, use DC appliances where possible, and avoid running resistive heat appliances from a battery.

Electric coffee makers, toaster ovens, space heaters, and induction cooktops can be useful, but they are high-draw tools. Run them deliberately. A 1,200-watt coffee maker may be fine on a large inverter, yet it can drain a modest battery surprisingly fast. Propane cooking and insulated bedding often make more sense than trying to power every home convenience from a compact battery.

When comparing portable solar generators, verify four specifications: continuous AC output, surge output, battery capacity in watt-hours, and recharge input. USB-only power banks are not camp power systems. Likewise, a big watt-hour number is not enough if the inverter cannot start your refrigerator or air conditioner.

Santa Fe Trail Supply Co. approaches power as part of a complete basecamp: shelter that stays deployed, shade that reduces heat load, and usable AC power for the gear that makes remote nights more comfortable. Size each part around the same question: what needs to work when the truck is gone for the day?

Buy enough capacity for your worst normal night, not your best-case afternoon. That margin is what keeps food cold, air moving, and camp comfortable when clouds roll in, temperatures climb, and the nearest hookup is miles behind you.