How Big a Solar Generator or Portable Power Station Do I Need?

"How big a solar generator do I need?" is the most common question we answer. The good news is that the math is simple and you only need three numbers: how much power your devices draw, how long you run them, and how much sun you get. This guide walks through the calculation step by step so you can choose a portable power station and solar panels that fit your plan, whether it is a camping weekend, an RV, or a backup for your home.

Solar generator, power station: what is the difference?

A "solar generator" is simply a portable power station (a battery with an inverter) paired with solar panels. The power station stores energy and delivers AC and USB power; the panels recharge it. Two ratings matter: watt-hours (Wh), which is the size of the fuel tank, and watts (W), which is how fast you can draw from it.

Step 1: list your devices and their watts

Look at the label on each device or its manual for wattage, or multiply volts by amps. Separate what you will run, and note which devices have a motor or compressor, such as a refrigerator, sump pump, or power tool, because they draw extra power when they start.

These numbers are examples to show the method, not measurements of any specific product. Check the label on your own equipment. A plug-in watt meter is an inexpensive way to measure real draw.

Step 2: calculate daily watt-hours

For each device: watts x hours = watt-hours. Add them up. In the example above the total is 2,610 Wh per day. If you do not need everything every day, calculate for the days of backup you want and multiply.

Add a cushion for inverter losses

Converting battery power to AC is not perfectly efficient. Jackery's sizing guidance suggests adding 10 to 15 percent for losses and gives the example that a 2,100 Wh need calls for roughly 2,500 to 2,800 Wh of capacity. Following the same approach, the 2,610 Wh example would call for a station of about 3,000 Wh or more.

Step 3: check running and surge watts

The station's inverter must handle the combined running watts of everything you plug in at once. Motor loads can briefly draw about two to three times their running wattage at startup, according to Jackery's guidance, so check both the continuous and surge ratings. If your total running load is 800 W and a compressor adds a startup surge, you want a comfortable margin above the sum, not a number that just meets it.

Step 4: size the solar panels

Panels determine how fast you refill. A simple planning formula is:

Daily watt-hours from solar = panel watts x peak sun hours x 0.75

Peak sun hours are the equivalent hours of full-strength sunshine each day. They vary by region and season, and a figure of about 4 to 5 hours is a common planning assumption for much of the U.S. in summer, less in winter. The 0.75 factor is a practical allowance for heat, angle, cable and charge-controller losses. For example, 400 W of panels x 4 hours x 0.75 = 1,200 Wh per day. Check the maximum solar input of your station so you do not buy more panels than it can accept, and confirm connector and voltage compatibility.

Step 5: pick a size range

These ranges are a starting point for matching your daily watt-hours to a class of station. Always confirm specifications on the product page, since they change between models.

For solar, a foldable panel such as the Jackery SolarSaga 100 Prime suits camping and small stations. Browse all of our solar panels if you need larger fixed or portable options, and Nature's Generator and Jackery for complete solar generator kits.

Common sizing mistakes

• Confusing watts with watt-hours. Watts are power right now; watt-hours are how long you can run.
• Ignoring startup surge on refrigerators, pumps, and tools.
• Forgetting that heating loads are hungry. Space heaters, electric kettles, and hair dryers can drain a station quickly. Plan on avoiding them unless the station is sized for them.
• Undersizing the panels and expecting a one-day recharge after a heavy-use day.
• Skipping the cloudy-day plan. Add a buffer day of capacity, or a way to charge from a wall outlet or vehicle.

When to move beyond a portable station

If you need to run a well pump, central air, or a whole panel, a permanent system with a hybrid inverter and a larger battery bank usually makes more sense. Our off-grid solar basics guide explains how those components fit together. You can browse portable power and off-grid solutions side by side.

Frequently asked questions

How many watt-hours do I need to run a refrigerator?

It depends on the model, but as an illustration, a refrigerator drawing about 200 W while running for 8 hours of a day uses roughly 1,600 Wh. Measure yours with a watt meter and add a cushion for inverter losses and compressor startup.

What is the difference between watts and watt-hours?

Watts measure how much power a device draws at a moment. Watt-hours measure energy over time. A 100 W device running for 5 hours uses 500 Wh.

How many solar panels do I need for my power station?

Use panel watts x peak sun hours x 0.75 to estimate daily solar energy, then compare it with your daily watt-hours. Also check the station's maximum solar input.

Can a portable power station run my whole house?

Generally not unless it is a large, expandable system with a high-output inverter, and even then it is best used for essential circuits. Call us and we will help you evaluate it.

Do I need to add extra capacity for inverter losses?

Yes. Jackery suggests adding about 10 to 15 percent to cover inverter efficiency losses.

Sources

• Jackery: common solar generator sizing mistakes (watt-hours, surge, 10-15% losses)
• U.S. Department of Energy: balance-of-system equipment for stand-alone systems