Solar panels

How to use this table

This table holds 22 solar panels normalized onto the same columns, so that units described differently by their manufacturers can be compared directly. Every row carries a confidence flag and a link to the datasheet or retailer page the figures came from, and every product has its own page with the numbers worked through for an off-grid build.

What is in here right now

The solar panels listed run from 100 to 550 W, with a median of 400 W. The median price works out at about $0.90 /W per unit, which is the figure worth comparing against rather than the sticker price.

Sort on any column by clicking its header. The comparison that usually settles a decision is not the biggest number but the price per unit alongside the specification that constrains your design, because that is where a cheaper product either is or is not a false economy.

What each column means

W

Rated output under standard test conditions in a laboratory. Real output is lower, and the gap is why system design uses peak sun hours and a loss factor.

Voc

Open-circuit voltage. Divided into a controller's input ceiling it gives the maximum panels in series, and it rises as temperature falls, which is the trap.

Vmp

Voltage at the maximum power point, which is where the panel operates when a tracker is doing its job.

Isc

Short-circuit current, used for fusing and combiner design.

Imp

Current at the maximum power point, which is what the wiring actually carries in normal operation.

Eff %

Watts per unit of area. It matters when space is the constraint and matters much less on open ground.

Cell

Cell technology, which affects low-light and temperature behavior more than it affects the headline rating.

lb

Weight, which decides how it is handled and mounted.

Fuse A

The largest fuse permitted to protect a string of these panels. A ceiling, not a recommendation.

Temp coeff %/°C

How much output falls per degree Celsius above the test temperature. Hot panels produce less than their rating.

Product wty

Product warranty, covering the item failing.

Perf wty

Performance warranty, covering output falling below a stated fraction of rating. A different promise from the product warranty.

Price

List or recorded retail price at the date noted. Prices move constantly.

$/W

Price normalized to the unit that allows fair comparison across different sizes.

A workable way to shortlist

Start with the array watts your load list and worst-month sun demand, then work backwards to a module count. Check the open-circuit voltage against the controller you intend to use, at your site's coldest temperature rather than at room temperature. Then compare price per watt, and only pay for efficiency if roof or rack space is genuinely the constraint.

Then read the individual product pages, which work each unit's published numbers through for an off-grid build and list the nearest alternatives in this table. The system planner sizes array, controller, battery, and inverter against each other rather than one at a time, which is how these choices actually interact.

Five ways people get this purchase wrong

1. Sizing the array on the annual average sun figure rather than on the worst month, then discovering the shortfall in December when every other load is at its peak.
2. Building a string to the controller's voltage limit as measured on a warm day. Panel voltage rises as temperature falls, and exceeding the limit destroys the controller outright rather than gradually.
3. Paying for efficiency where space is not the constraint. On open ground, more of a cheaper module is usually the better buy for the same total watts.
4. Skimping on the array run. Voltage drop between panels and controller is a percentage of every kilowatt-hour the system will ever produce.
5. Ignoring the winter horizon. A site that is sunny in June can lose the middle of the day to a ridge or a stand of conifers in December.

Every one of those is cheaper to avoid than to fix, and most of them are decided before anything is bought. That is the argument for building the load list and the system design first and shopping second, which is what the planner and the course are for.

Where these numbers come from

Figures are transcribed from manufacturer datasheets or primary retailer specification pages, recorded with a date and a confidence flag, and linked back to the source on each product page. Where a manufacturer publishes a figure without its test conditions, it is recorded as published and treated with the skepticism it deserves rather than quietly normalized.

Prices are list or observed retail at the date noted and move constantly, so they are here for the ratio rather than for the last dollar. The price index tracks market ranges over time, the open data page publishes these tables as CSV and JSON, and the methodology page sets out how the research is done. If a figure here no longer matches its source, the corrections page is how to say so; corrections are logged publicly rather than edited away.

Missing a product you are comparing? Tell us and it goes on the list. The tables grow from what readers are actually shopping for rather than from what is easiest to transcribe.

Common questions about solar panels

How many panels do I need?
Divide your daily energy use by the peak sun hours available in your worst month, then add roughly 20 to 25 percent for wiring, temperature, soiling, and conversion losses. That gives array watts; divide by the module rating for a count. Sizing on the annual average instead of the worst month is the most common way to end up short in December.

Are more expensive panels better?
Rarely in ways that matter off grid. Most current modules from established manufacturers perform close to their ratings and degrade slowly. Higher efficiency buys watts per unit of area, which is worth paying for when roof or rack space is the binding constraint and not otherwise. Compare price per watt, and remember racking and wiring do not get cheaper with a cheaper panel.

Can I mix panel models in one array?
Within a string, no, not sensibly: series-connected panels should match in current and ideally in voltage, because the string is limited by its weakest member. Different models can run on separate strings or separate trackers. If you expect to expand, buying enough of one model now is usually cheaper than matching a discontinued module later.

What does the temperature coefficient actually cost me?
Output falls as the panels heat up, so a hot roof in July produces meaningfully less than the rating suggests. In the other direction, cold raises voltage, which is what threatens a controller's input ceiling on a clear winter morning. The first effect costs you energy; the second can cost you equipment.

Is bifacial worth it?
On a ground mount over a reflective surface such as snow or light gravel, it can add useful yield in exactly the season an off-grid system is short. Flat against a roof it adds nothing. Judge it by the mounting you actually plan rather than by the specification.

Listings, inspection, and insurance

Safety listings are easy to skip past on a spec sheet and hard to add afterwards. Where a jurisdiction inspects an off-grid installation, unlisted equipment can fail the inspection outright. Where nobody inspects, insurers may still ask, and an appliance or a system component without a recognized listing is a reason some carriers give for declining a rural policy or a claim.

That matters more off grid than on, because rural policies are already a narrower market. Insurers commonly ask what the structure is, how it is heated, how far it is from a responding fire station, and whether the installation was permitted and inspected. Deciding to buy listed equipment and to hold the installation to code standards, even where nobody will check, is the cheapest form of that conversation going well.

Keep the paperwork with the systems binder: model and serial numbers, the datasheet as it read on the day you bought, the installation photographs before anything was closed up, and the receipts. Proving what you had is your job in a claim, and it is also what makes a sale straightforward years later. Lesson eleven covers the insurance and financing side, and the printable binder has a place for all of it.

This category inside a whole system

No component in an off-grid power or water system is chosen alone. The battery constrains the inverter, the inverter constrains the cable and the fusing, the controller constrains the array, the array is constrained by the worst month at your location, and the whole thing is constrained by the load list you started with. Choosing any one part in isolation is how people end up buying twice.

The order that works is: honest load list, then location data, then system voltage, then the components against each other, then the wiring and protection that make it safe. Lesson four covers the load list, the site report gives the location numbers for any address, the planner sizes the components as a set, and lesson six covers the part where mistakes start fires rather than merely costing money.

The other tables are next door: batteries, panels, inverters, controllers, generators, and pumps. For prices rather than specifications, the price index; for what to keep on the shelf, the spares reference; for the terms used here, the glossary.