Solar generators for home backup

The phrase covers two products. One is an all-in-one box with a battery, an inverter and a solar input, sold alone. The other is that same box bundled with one or two folding panels and sold as a solar generator. The hardware is identical; the bundle only decides whether you can recharge without a wall outlet.

That matters for backup because a wall outlet is exactly what is missing in an outage. A box bought alone is a very large phone battery during an outage: it works until it is empty, then it is a brick until the grid returns. The panels are not an accessory in this use case, they are the recovery path.

This page is about the second question, which almost no listing answers: after the first night, what happens. It is not a ranking by capacity, because capacity alone is the least interesting number here.

Every listing carries three figures that matter and half a page of figures that do not. Reading them in this order prevents most of the expensive mistakes.

Capacity is deliberately fourth. It is the number every listing leads with, and it is the one that matters least on its own, because a bank that cannot be refilled is a countdown rather than a system.

For the output and surge side, the power station match calculator runs the three checks against your own load and names the smallest unit that clears them.

Survive means the box carries the kit until the battery is empty. Sustain means the panels replace what the kit uses, so day four looks like day one. The difference is arithmetic, and it is decided before the purchase.

A 300 W continuous kit uses 7,200 Wh a day. That is a lot: it assumes every appliance in the kit runs around the clock, which is what an average figure implies. Real kits cycle, so the honest comparison is against the duty-cycled figure, which is usually a third of it.

The lesson in that table is uncomfortable: doubling the battery buys hours, and doubling the panels buys days. Households buy the battery first because it is the visible part, then discover the panels were the constraint.

The battery sizing calculator starts from generation for the same reason, and the sun hours table gives the location figure that makes the arithmetic real.

Take the first row of the table below as the test case. A 1,024 Wh bank at 85 % depth of discharge gives about 870 Wh of usable energy, so a 150 W continuous load drains it in 5.8 hours. The same kit carries 400 W of panels, which at 4.5 sun hours and 80 % efficiency makes about 1,440 Wh a day, while the load uses 3,600 Wh across those 24 hours. The battery decides the first night and the panel decides whether there is a second one, and neither number substitutes for the other.

Solar input is capped per unit, and the cap is usually well below the panel array people imagine. A unit that accepts 400 W will never use an 800 W array fully; the extra panels sit in the sun doing nothing. That is why the input figure, not the panel count, sets the recharge time.

There is also a seasonal trap. Sun hours drop by half in winter across most of the country, so a pairing that sustains in July can drain in January on the same hardware. Sizing on the annual figure is the single most common error in this category, and it always looks fine in summer.

Avoiding it is simple: use the winter figure for anything that must work in winter, and accept the overproduction in summer as the cost of the guarantee.

Two practical examples of the cap biting. A 1,070 Wh bank paired with two 100 W panels recovers slowly even in July, and adding a third panel does nothing unless the station accepts it. A 2,042 Wh bank with two 200 W panels is the better shape of the same purchase, because the array and the bank grew together.

Thirteen bundles appear in the current US market, eight with a battery and panels together and five panels sold separately. The entries below are ordered by capacity for the kits, and by wattage for the panels; none of them is a recommendation to buy a specific model, and the figure to compare is the pairing, not the badge.

If you only want the three shapes that cover most households: the 768 Wh starter pairing for a phone-and-lamp outage, the 1,070 Wh kit with a 10 ms transfer when a desktop has to stay up, and the 1,024 Wh unit with a published 3,000 W surge when a motor is in the kit.

The panels matter as much as the boxes, so they are listed separately. Each of these is a folding panel that can feed a station directly, and the input cap on the station is what decides how many are useful.

One further panel, the Anker SOLIX PS400, is sold from the manufacturer's own store rather than through a retail listing, so it carries no link here. It is a 400 W bifacial option for anyone already inside that ecosystem.

For the station side on its own merits, the portable power station ranking compares the same boxes on capacity and output without the panel question.

Some units quote a transfer time in milliseconds. That figure describes how quickly the box switches from wall power to battery when the grid fails, and it decides whether a desktop, a router or a medical device keeps running or reboots.

Ten to twenty milliseconds is fast enough that most electronics do not notice. A second is not, and a unit that does not quote the figure at all is not necessarily slow, but you cannot tell from the listing.

This is the one place where a smaller box can legitimately beat a larger one for a specific job: if the thing you are protecting is a computer, the transfer time matters more than the kWh behind it.

These units output 120 V. That single fact rules out a list of appliances that people most want to run during an outage, and it is worth knowing before the purchase rather than after.

Everything else in a normal backup kit is 120 V and within reach: a fridge, lights, a router, a fan, a phone charger, a laptop, a CPAP without a heated humidifier. That list is genuinely enough for most outages, which is why the category sells at all.

Four figures, in order. Capacity tells you the size; continuous output tells you whether the kit starts; surge tells you whether the motor starts; solar input tells you whether it comes back. If the listing omits the surge or the input, the answer is that the seller has not told you, which is different from a no.

Then divide capacity by your kit's running watts. A 2,048 Wh unit at 85 % is 1,741 Wh, so a 300 W kit runs 5.8 hours, not eight. That single division corrects the most common expectation of this category.

Finally, compare daily generation against daily use. Four hundred watts of panels at 4.5 sun hours and 80 % efficiency is 1,440 Wh; if the kit uses more than that, the setup is a countdown. This is the number the marketing never puts on the page, and it is the one that decides day four.

Buying capacity only. A big bank with small panels is a countdown, and a big bank with a small inverter cannot start the load.

Sizing on summer sun. Winter halves the sun hours across most of the country, and an outage in January is not unusual.

Buying panels bigger than the input. The station cannot use what exceeds its cap, so the extra panel is decorative.

Assuming the box runs the house. It runs a kit, and the 240 V appliances are simply out of scope.

Forgetting the transfer time. The box can be full and still reboot the computer it was bought to protect.

If a figure here disagrees with a calculator on this site, the calculator is the source of truth and the changelog records every correction.

It leaves out price, deliberately, because a printed price is wrong within weeks and this site does not state product prices. It leaves out hands-on testing, because this site does not buy or test hardware. And it leaves out an ordered top pick, because the right answer depends on a kit and a location rather than on a product.

The honest version of this category is that two boxes with the same capacity can differ by a factor of two in what they are worth to a given household, and the difference lives entirely in the output, surge and input columns.

Three neighboring calculators cover the parts of this question that are not about the bank: the charge controller sizing calculator for the panel-to-battery side, the unit converter for amp hours and watt hours, and the system comparison calculator for whether storage pays at all.

Choosing between a battery and a fuel generator instead? See solar generator versus gas generator.

For the outage-length arithmetic behind these picks, see the outage capacity calculator.