By Chris O’Brien, SunPower Corporation

5 June 2013 — Putting a solar panel on your roof isn’t the end of the story. Will it work as intended? Will it continue to produce the energy  promised? SunPower managing director Chris O’Brien, whose company offers warranties on its products explains some of the traps and how to avoid them.

We have reached a point in Australia where solar photovoltaic systems are viable and economically attractive alternatives to traditional sources of power. Highly efficient panels and reliable technology are critical to a successful solar investment, as are comprehensive, long-term solar power system warranties. Understanding these warranties is integral to making any investment decision in solar and can help consumers make a more informed choice.

What solar warranties cover and for how long

Most solar manufacturers offer customers separate “product” and “power” warranties, which can lead to confusion as the physical panel and the power generated are inextricably linked. If a panel begins to degrade or malfunction, it will therefore be producing less energy than expected. The reverse is also true. If a panel is producing less energy than expected, chances are high that it has begun to degrade or malfunction. In these instances, it can be difficult for consumers to determine if the core issue is covered under a product or power warranty.

Warranty lengths differ by manufacturer and geographic market, however most power warranties are for 25 years while product warranties typically range from two to 10 years.

Guaranteed power

Understanding how much power output a manufacturer or supplier guarantees that a panel will deliver is essential to assessing expected degradation and, therefore, minimum energy production of the complete solar photovoltaic system. The power output guaranteed at the end of the warranty term can also be used to gauge a system’s residual value.

Two types of warranty

There are two main types of power warranties: step and linear.

A step warranty is the most common, guaranteeing a minimum percentage of a panel’s original rating over time (90 per cent for the first 10 years, for example). It then steps down to a lower percentage (usually 80 per cent), which is guaranteed for the next period of time until there is another drop in guaranteed power or the warranty expires.

A linear warranty typically guarantees a minimum panel output of between 95 per cent and 97 per cent for the first one to five years with a degradation rate of between 0.4 and 0.7 per cent each year for the remaining years. Lower guaranteed degradation rates consequently translate to more energy over the life of the system. Under linear warranties, a panel can be guaranteed to produce 80 to 87 per cent of its original power output level at the end of the warranted period.

Avoiding a solar panel warranty claim

Selecting a robust and reliable panel is integral to reducing the need to make a warranty claim. Panel certifications, while helpful in ensuring the product meets a minimal performance and safety standard, are not designed to assess how a solar panel will function over its lifetime.

Third-party studies challenging the safety certification benchmark are helpful in evaluating a panel’s susceptibility to degradation and failure caused by environmental stresses.

One might consider studies conducted by Fraunhofer Institute for Solar Energy Systems, an international testing agency and the largest solar energy research institute in Europe with more than 60 years of experience conducting research on energy efficiency technologies.

PHOTON Laboratory GmbH is an organisation that has been testing solar panels independently since 2009. One of its studies is the long-term module yield test which observes more than 170 module types in an outdoor setting. This particular study measures a panel’s yield, or how many kiloWatt hours per kilowatt of installed power flow from the photovoltaic system to the inverter. The test is performed independent of other system components, in real-world conditions.

An informed customer will consider these and other prolonged testing from independent third parties as an indicator of panel reliability and performance.

Costs associated with fixing an underperforming solar panel

When calculating the return on investment of a solar asset, it is important to consider the likelihood that a panel will fail and the projected costs associated with fixing it.

With some warranties, a claim for an underperforming panel will result in a one-time payment at the current market rate for every watt below a panel’s warranted power level or a component replacement, dependent on the manufacturer’s discretion.

To minimise inconvenience and have a clear projection of lifecycle costs, any company considering a solar system installation should ask the following of their provider to better understand their recourse in the event of a warranty claim:

  • Is delivery of a replacement panel included as part of the warranty
  • Is installation of the new panel included as part of the warranty
  • Is removal of the troubled panel included as part of the warranty
  • Who is responsible for boxing and shipping it back to the manufacturer

Ensure manufacturers will be around to honour the warranty

In addition to proof of a solar manufacturer’s reliable core technology and ability to successfully serve customers over a product’s lifetime, economic stability of the company is crucial. Organisations with strong financial backing and a diverse offering of quality energy solutions will best suit consumers in the long run, should their solar system begin underperforming within the next 25 years.

Chris O’Brien is the managing director of SunPower Corporation in Australia. He says SunPower offers a 25-year combined power and product warranty on its solar energy systems.