Solar power is contagious. These maps show how it spreads.

Brad Plumer for VOX:  Rooftop solar is expanding rapidly in the United States — by some estimates, a new system goes up every four minutes. There are plenty of reasons for that, from falling prices to generous federal subsidies to innovative leasing schemes.

But there's another, little-discussed factor here: Residential solar power is contagious. Yep, contagious. Studies have found that if you install solar photovoltaic panels on your roof, that increases the odds that your neighbors will install their own panels.

SolarCity, the largest solar installer in the United States, just published some fascinating data on this "contagion" effect. The company has installed 230,000 rooftop systems nationwide (often by allowing customers to lease panels rather than buy them upfront). It says fully one-third of customers were referred by a friend or neighbor.

SolarCity has also made some neat animations showing the "contagion" effect in action.  View here:

Small-scale solar power growing in the United States

By Daniel J. Graeber for  Small-scale solar installations in the United States account for about a third of the overall capacity on the grid, a report from the federal government said.

The U.S. Energy Information Administration estimates total U.S. solar-power output in September, the last full month for which data are available, at 3.5 million megawatt hours. Of that, just more than 30 percent came from small-scale solar installations.

"Generation from roof-top photovoltaic systems has become an increasingly important part of total solar generation in the United States," EIA AdministratorAdam Sieminski said in an emailed statement.

A September report from the Solar Energy Industries Association, with support from green energy market adviser GTM Research, found second quarter residential solar capacity grew 70 percent year-on-year to 473 megawatts.  Cont'd...

Are Energy Free Homes Practical?

Energy free residences are not only practical but they are the dwellings of the future. Let's hope that home builders start thinking zero net energy as they design upcoming housing subdivisions.

Mechanical ventilation and heat recovery System with integral heat pump

This article explains: some background to our bungalow design, why we had the original mechanical ventilation and heat recovery system installed; why we chose the latest system and our experience with both systems.

What Size Air Conditioner Do I Need?

Many people mistakenly buy larger air conditioning units than they need because they believe that a larger unit will both operate and cool their house more efficiently. In truth, a larger unit could be less efficient.

The Cutting Edge of Sustainable Home Design

One university's quest to revolutionize the built environment.


BeyWatch is a 30-month research project supported by the European Commission (DG Information Society and Media) aiming at ICT tools for environmental management and energy efficiency. BeyWatch develops an energy-aware and user-centric solution, able to provide intelligent energy monitoring/control and power demand balancing at home/building & neighbourhood level.


How many of us defrost frozen meat with running water instead of letting it thaw in the fridge? How many times do you use the hose to sweep off the driveway when a broom can be just as effective?

Greenroofs benefits outweigh costs, even in desert environment.

The only severe downsides of having greenroofs in a desert climate are cost of installing it, and then the water use for irrigation. But as we'll see, the water needed for irrigation is more than covered by available greywater.

Rebuilding a Green New Orleans

All in all, I am impressed with some of the strides that have been taken in rebuilding the coast with green in mind. While by no means is it an end to the challenges on being more efficient and using more alternative energy, it is a a start.

Engineered Garden

I started my sustainability project with a theme, "Grow What You Can Eat." It was my hope to use natural free resources water and solar energy to live a more sustainable lifestyle. Though the progress may be slow, I am proud to see the changes that my neighbors and other communities have made in realizing the value of this global issue to be solved by each one of us. As a specialist in the education and implementation of water conservation and rain water harvesting, we all should take small steps with end goal of someday achieving total sustainability.

First Renovated Residential High-Rise Worldwide to Reach Passive House Standard

Fraunhofer ISE Accompanies the Energy Renovation and Monitors Operation

Residential Geothermal Install Case Study

When Tim and Tracy Gilchrist sought an alternative way to heat and cool their non- traditional home in Laurentian Valley, Ontario, little did they realize what a noticeable impact their decision would have on their children and pets.

It's Not About Being Green

Before you decide to hop onto the green building bandwagon, look towards the final destination. Sustainable, integrated, whole-building design is where to head.

Greening Affordable Housing

The green building techniques used by HEB are not radical, and should be accessible to any builder.

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