Many people are well-acquainted with the concept of solar energy — photovoltaic panels produce electricity by being exposed to the sun. But not many people are familiar with how solar panels work. While there’s plenty of scientific literature explaining the photovoltaic effect, the actual panel itself is relatively simple — it contains silicon solar cells, an aluminum frame, glass casing, and wires.

That’s it. No moving parts, no liquids. While there are different types of panels — namely monocrystalline and polycrystalline panels — the physical composition of each is fundamentally similar. Solar systems don’t require you to climb up and tighten bolts or change fluids; in climates like New York that have four seasons and regular rainfall, there’s no need to brush dust off the panels either.

Solar panels simply work without interruption, which is why manufacturers are comfortable standing by their products for far longer than most other consumer technologies on the market.

All solar panels, regardless of type, can degrade in efficiency over time, but the allowable range of degradation can vary. While photovoltaic cells aren’t new, they’re affected differently on earth than they are in space. The primary causes of solar panel degradation arise from exposure to the elements, so panels with higher tolerances for exposure to harsh weather tend to have better warranties against degradation.

That said — panels are guaranteed to perform, not to degrade. In the past, standard performance warranties allowed for a minimum level of performance over twelve years, and then a lower allowable minimum over the following thirteen, totaling twenty five years.

Modern monocrystalline panels will also provide a twenty five year warranty, but it’s linear — meaning a panel that degrades in efficiency too quickly would trigger the warranty and get replaced. Homeowners can monitor their systems using a custom monitoring application. The current industry standard for acceptable linear degradation is generally around 80% production in year 25.

Some manufacturers, such as Q-Cell and Solaria, are able to offer higher production guarantees over 25 years. These panels warranty 85% and 86% production respectively in year 25, compared to the standard 80%. Again, panels aren’t guaranteed to degrade, but manufacturers that incorporate stricter manufacturing controls and higher end materials are more willing to stand by the performance of their panels.

If you live in a home that has a large overhanging tree branch, you may be wondering, “What happens if something falls onto my panel and breaks it?”

The same question applies in other circumstances in which a high speed or heavy object might crash into your panels. The answer to this question in both circumstances is that it would not trigger either warranty from the solar panel manufacturer, and you’d want to consult your homeowner’s insurance provider.

Once the solar system is installed on the home, it’s considered part of the property, just like a central heating unit. Many insurance providers don’t have specific riders for solar panels, although you should consult your specific insurer regarding your policy to make sure it is covered the same way as your siding, roof, kitchen, and so on.

You may remember from science class that there are different types of electrical current we use in day-to-day life — alternating current (AC) and direct current (DC). Alternating current moves in an oscillating flow that switches between positive and negative directions; direct current moves in a constant flow in one direction. A lot of technologies either receive or use electricity in DC, such as laptops or flashlights; AC electricity is highly efficient at transmitting power at low voltages and over long distances, which is why we use it to send electricity from power plants to our homes.

Solar panels produce electricity in DC, but our electrical grid and homes transfer electricity in AC. Solar systems use a device called an inverter to convert the electricity from DC to AC before it enters the power grid.

There are two different types of inverters used in solar systems — string inverters and microinverters. There are plenty of differences between the two, but manufacturers of both provide a warranty for the inverter performance.

String inverters are the more traditional type of inverter used in solar systems. They’re called such because each panel was wired from one to the next, connected on a “string”, and the system would feed into a central inverter. This central inverter would ideally be installed in a location protected from natural elements, such as on the side of the house in the shade or possibly in the garage.

There are some drawbacks to this traditional type of inverter, notably that the system output was measured by the least productive panel; in addition, if one panel stopped working, the entire system would shut down. Lastly, DC electricity loses efficiency when traveling over distances, which can have a measurable effect even on residential systems where the inverter is installed far from the arrays (some systems offset this with power optimizers; more on that later.)

The longevity of your string inverter may come down to the experience of your contractor. Inverters are designed to periodically handle higher-than-normal loads (e.g. on an exceptionally sunny day), but an inexperienced contractor might install a string inverter based on this peak capacity rather than the normal safe operating threshold. Since a string inverter converts power for the whole system, this would cause the inverter to burn out much quicker than expected.

String inverters typically come with 10-12 year warranties to cover their performance under proper installation. Details may vary between products so you should consult the spec sheet for specifics.