How Home Solar Works in 2026

The pieces on a typical roof

Most grid-tied homes have modules, racking, an inverter, and a connection to the main electrical panel.

A photovoltaic module is a sealed sandwich of cells, glass, and a frame. Cells produce direct current when light hits them. The Department of Energy's solar photovoltaic overview is a short public description of that step. Racking holds the modules to the roof structure. It is not decoration. The lag bolts and flashing are what keep water out of the deck.

An inverter turns direct current into alternating current the house can use. String inverters put that job in one box, often on a wall. Microinverters and DC optimizers do part of the work at each module, which can limit how far shade on one module drags down the others. Neither design removes the need to look at the roof.

The system lands in the main service panel, behind a disconnect the utility and the fire department can find. A production meter or the inverter's monitoring tells you what the array made. The utility meter still records what you bought, and on many tariffs what you exported.

A battery is optional equipment, not a required part of making solar electricity. Batteries and backup covers what a battery can and cannot keep running. If the sales visit treats the battery as mandatory before anyone has asked what you want on during an outage, slow the conversation down.

Kilowatts and kilowatt-hours

Kilowatts are the size of the system. Kilowatt-hours are the energy it makes, or that you buy.

A 7 kW system is a capacity rating, usually in direct-current watts of the modules. It is not a promise of 7 kW every hour. Output moves with sun angle, clouds, heat, and shade. Over a month the useful number is kilowatt-hours, the same unit as the usage line on a bill.

Berkeley Lab's August 2026 data update reported a median U.S. residential system size of 7.7 kW for 2025 installs, with most systems roughly between 5 and 12 kW. That is a description of what was installed, not a target for your roof. A small efficient house in a mild climate can be well served by less. A large all-electric house in a hot climate can need more than the roof can hold.

Our estimate starts from the bill you type and a state average price, then illustrates covering 70 to 90 percent of that annual bill before shade. Sun hours change the illustrated size in kilowatts. They do not, in that illustration, change the dollar range, because the dollars are a share of the bill. Read that sentence twice before you compare it with a proposal. A proposal prices equipment. Our page does not.

What the sun actually does on a roof

Production follows the weather and the calendar. A south-facing, unshaded roof makes more than a shaded east-facing one, and hot modules make a bit less than cool ones.

Peak sun hours are a way to describe the resource: how many hours of full-strength sun the energy in a day would equal. NREL's National Solar Radiation Database is the public record behind tools such as PVWatts. A statewide figure hides the difference between a coastal roof and a desert roof. City pages on this site use a metro-level approximation and say so.

Azimuth is the compass direction. In most of the United States, south-facing arrays produce the most across the year. East and west still work. West can line up better with late-day air conditioning, which matters when the utility pays less for midday exports than it charges for evening purchases. Tilt is the slope. A roof that is already near latitude tilt is convenient. A flat roof can use tilted racks if the structure and the wind design allow it.

Heat is the part of the brochure that gets skipped. Crystalline modules are rated at a mild cell temperature. On a hot roof they run hotter, and output drops a little for each degree. That is one reason a sun-hour map is not a production guarantee. Snow and cloud cover, which matter in our active states, cut production the other way. Soiling does the same job more slowly.

Shade is local and often decisive. A vent pipe, a chimney, or a neighbor's oak can cut a string of modules even when the rest of the roof is bright. Our form asks for a rough shade description and reduces the illustrated range. It is not a shade study. A site visit with a sun-eye tool, or at least a honest look at the horizon, still has to happen before a price means anything.

The grid is still part of the system

Unless you have a battery and the right transfer equipment, a grid-tied array shuts off in an outage so it does not energize a line a lineworker is repairing.

That shutdown is a safety rule, not a defect. People are sometimes surprised by it because the sales story sounded like independence. Independence from the utility, if that is the goal, is a battery and a critical-loads panel, designed on purpose. Even then, a battery has a finite number of hours. Whole-home backup of air conditioning through a long outage is a large battery, not a slogan.

During ordinary days the house uses solar first, buys the rest from the utility, and may export the surplus. What that surplus is worth is net metering, or whatever replaced it on your tariff. Some utilities still credit a kilowatt-hour with a kilowatt-hour. Others pay an avoided-cost or time-varying export rate that is well below the retail price. Our estimate values offset energy at the state average retail price so the math is visible. If your export credit is lower, the real bill impact is smaller. The page says that because hiding it would make the estimate look like a quote.

You will still have a utility relationship. Minimum bills, customer charges, and demand charges do not disappear because modules are on the roof. Time-of-use rates can make the hour of production matter as much as the annual total. Bring a recent bill to any serious conversation. The rate schedule name on the bill is more useful than a statewide average.

How long the equipment is expected to work

Many module warranties run 25 years for product defects and a separate performance guarantee. That is a contract, not a prediction that nothing will fail.

NREL's review of field degradation, the Jordan and Kurtz paper, found that a median module lost about half a percent of output per year, with a wide spread. Newer products can do better or worse. A half percent per year is about 12 percent over 25 years, which is why performance warranties often promise something in the neighborhood of 85 to 92 percent of nameplate at year 25. Read the warranty you are offered. The number is not universal.

Inverters often carry a shorter warranty than modules. A string inverter replacement is a known mid-life cost. Microinverters spread that risk across the roof and can be more expensive up front. Racking and flashing should last with the roof, but a reroof means the array comes off and goes back on. If the roof is near the end of its life, do the roof first or get the removal and reinstall priced in writing. Skipping that is how a cheap solar price becomes an expensive roof job.

Monitoring is how you notice a failure. A system that quietly produces 30 percent less for a year is a lost year. Ask who watches the portal, what happens if the installer closes, and whether you can see production without their login. Those are ordinary ownership questions, not gotchas.

What our estimate is doing with your bill

We divide a typical monthly bill by the 2025 EIA state average price to sketch usage, then illustrate offsetting most of that usage.

EIA's Table 2.10 price is utility revenue divided by kilowatt-hours sold. EIA explains that this average is not a rate schedule. It includes delivery, generation, and many fees, blended across every residential customer in the state. It is a fair public input for a first look and a poor substitute for the tariff on your bill.

The dollar range is 70 to 90 percent of the annual bill before shade, or less if you tell us the roof is shaded. The 25-year figure is 20 to 25 times the annual number. It ignores the cost of the system, loan interest, degradation, rate changes, and export rules. We print those omissions next to the number. If a proposal's savings chart does not list its own omissions, ask for them.

After the estimate, you can request a call. American Solar Savings introduces you to a local installer. We do not install the system and we do not set the price. The installer should do a site visit before anyone treats a number as a bid.