clock menu more-arrow no yes mobile

5 Things You Need to Know About Solar | This Old House: Live

Ask This Old House home technology expert Ross Trethewey breaks down the five most important things to consider before installing solar panels on a house.

Are you looking to install solar panels on your house, but not sure where to begin? From panel types to financing, we break down the 5 things you need to know about adding solar to your home.

Is your house a good candidate for solar?

The ideal candidate for solar is a house that has:

A New/Young Roof

The typical roof lasts about 20-30 years. If your roof is old, please put a new roof on before installing solar on it. Solar systems last at least 25-30 years, or longer. If the roof structure is old, you may need to get a structural engineer to verify the load imposed by the solar system is adequate.

Minimal Shade

If there are trees or other obstructions that cause the majority of your roof to be shaded, then solar might not be the best option. Maybe I’m stating the obvious, but the panels need sunlight for them to work, so more shade means less available energy.

Few Obstructions

The more solar panels you put on your roof, the more solar production they are capable of. However, if you have obstructions like dormers on your roof, those areas of the roof will provide less area for panel. Obstructions also make the installation more challenging and often create shade in mornings and afternoons when the sun is lower in the sky.

A South-Facing Roof

At least in the Northern hemisphere, the south side of any building gets more sunlight, so south-facing roofs can generate more electricity. However, don’t be disappointed if you have an east/west roof, since it’s not a deal breaker; they lose about 20% in output when compared to a solar array oriented south.

Types of Solar Panels

Holding a solar panel

Another thing to consider is what type of panel you’d like to have installed. There are three main types:


These are panels that are made up of solar wafers manufactured from a single silicon crystal. These are considered premium panels and have some of the highest efficiencies, usually about 17-22% more than other panel types.


Similar to mono, however, these wafers are made from melting many silicon fragments together to form a single wafer to collect energy. They’re less efficient than mono (typically 13-17% efficient) but at a lower price point.

Thin Film

A process of applying layers of PV material to a substrate that can produce electricity. They have the lowest efficiency of the three types (typically 10-13%), but they are lightweight and can be flexible.

The technology is still pretty new and developing on this one. Some of these products are being integrated with common building materials such as roof shingles or windows. Ross sees this trend growing and thinks there’s a potential that in 5-10 years, this could be the more standard form of solar.

Inverter Types

Solar energy creates DC, or direct-current, power. Our houses use AC, or alternating current. To convert the sun’s energy from DC to AC, the solar panels require an inverter. There are three main types:

String-inverters/‘Central Inverters’

These inverters connect all the panels together as one unit, which means that the panels can only produce as much energy as the weakest panel in the array. This is the most common inverter type for solar installations and it’s also the most cost effective.

Power Optimizers

Similar to a string inverter system, but each panel gets an “optimizer’, which allows each panel to perform at its individual maximum capacity. It still requires a central inverter to convert the energy, and its price point typically falls in the middle between string-inverters and micro inverters.


These inverters convert the energy from DC to AC at each individual panel, thereby eliminating the need for a central inverter all together. This system offers optimum performance, especially on roofs with lots of shading/obstructions, but it is the most expensive and has the most moving parts. One other advantage is it allows for future expandability of the system, so if you wanted to add more panels to the same system later, this might be the best choice.

How to Finance Solar Panels

There are three main models that you can look into for payment:

Own (purchase with cash)

This purchasing method is when you buy the entire unit outright, which is an expensive upfront cost. Since you own the panels, you’re also responsible for upkeep and maintenance on the panels. However, owning the panels makes you eligible for tax credits/rebates/SREC’s. Financially, this is typically the best option, as it eliminates your electric bill and pays for itself sometimes as soon as 7 years.


Similar to owning the panels, in this circumstance you’d pay off the panels by spreading out the cost over a longer time period, typically 10 years and paying some interest. This can often be structured while paying sometimes as little as $0 down. The monthly payments are usually a little bit more than an energy bill, unless you are in a location with robust solar rebates or SREC’s.


In this case, you are effectively renting your roof to a third party who puts solar panels on it. The lease or PPA (power purchase agreement) is structured in a way so that you save a small percentage, typically 10% off your electric bill. You aren’t responsible for maintenance on the panels, so there is less risk, and you also do not have to pay any money out of pocket, but it’s the least financially rewarding.

Another Quick Note: With all loans and leases be sure to read the fine print of the agreement with respect to selling your home, and end of lease. You want to make sure they are transferable in the event you sell your home.


If you purchase your panels, there are a couple types of warranties offered:

Manufacturer ‘Performance’ Warranties

These protect the panels to ensure they produce close to their maximum power over their lifespan. They are typically structured as at least 90% capacity for the first 10 years and 80% after that with a typical life expectancy of at least 25 years.

Manufacturer ‘Equipment’ Warranties

These ensure that the manufacturer will replace the panels, cables or inverters if they fail due to damage. However, they typically do not cover the labor to replace.

Installer Warranties

For a fixed time period (typically 1 year, but sometimes up to 5 years), these will cover the labor costs if any part of the system malfunctions.

The good thing about solar is there are very few moving parts, so there are very few items to fail. That being said, make sure you keep the squirrels out with a squirrel/critter guard, they love to chew wires!

In general, before you commit to solar, ask friends, family, and neighbors for reputable solar companies. Do your research online; there is a host of solar quoting companies and lead generation services out there. Make sure you choose one that is financially solid, has a decent company lifespan, and has proper certifications. It varies state by state, but North American Board of Certified Energy Practitioners (NABCEP) certified is a must. Also, I like to see Certified Solar Roofing Professional (CSRP) along with some others.

Good luck!