How Much is Too Much Solar?

By Liz Ross, Ph.D. Candidate in the Applied Social and Health Psychology program, a trainee in the CSU InTERFEWS Program, and a graduate intern at the National Renewable Energy Laboratory

It’s the year 2030 in Fort Collins, CO, and you’re interested in installing solar panels on your home. Many of your neighbors are already enjoying the benefits of having solar on their homes — their energy bills are cheaper because they produce their own electricity; their property values have increased because rooftop solar is desirable to buyers; and their carbon footprint is lower because their energy source relies on the sun.

You get bids from solar contractors, and you’re ready to switch to solar. However, when you contact Fort Collins Utilities, to your dismay, they tell you that you’re not allowed to install the panels on your home. Although many residents have enthusiastically adopted solar panels, they didn’t do so uniformly — some neighborhoods, including your own, saw more solar installations than others. This means that the city has to turn away interested users, like yourself, before the feeder lines, which distribute electricity to customers, become overwhelmed. Could this problem have been prevented? Using certain types of analyses, called hosting capacity analyses, we might have been able to predict this problem and help the city prevent it, allowing you and others to install solar panels freely.

My research team and I are currently attempting to do just that.

Electric grids are currently designed with a specific purpose — to deliver electricity to our homes and businesses. Traditionally, electricity is created at one point along the grid and is then distributed by feeder lines. When rooftop solar panels are installed, the feeder lines suddenly have to deal with multiple electricity input points; electricity enters the grid at the traditional generation site and at each building that has rooftop solar installed. Further complicating the situation, certain parts of the city might see greater increases in solar installation than others. For example, areas with more rental properties might have less rooftop solar installed than areas with more owner-occupied homes. In addition, older homes might be less suitable for rooftop solar than newer homes.

This is not a problem if the number of rooftop solar installations does not exceed a certain amount; however, if enough homes install rooftop solar, problems could arise. Each feeder line has a capacity limit, meaning that it can only handle a certain amount of additional generation. Once a certain amount of rooftop solar is installed, those capacity limits can be violated. At that point, the city would have to either restrain the expansion of rooftop solar or upgrade the electric grid to increase the feeders’ capacity limits, which could lead to delays in service.

My Colorado State University research team and I (Dr. Patricia Aloise-Young and Jerry Duggan) are social and computer scientists, and we are conducting analyses to help the city stay ahead of this potential problem. Traditional ways of studying feeder capacity limits do not take into account the fact that certain neighborhoods are likely to see greater rates of installation than others. To remedy that, we are using existing data regarding patterns in current solar panel adoption to create a model that describes the different rates of adoption across the city. Our model will tell us the probability that each residential property in Fort Collins will install solar, and we can then incorporate those probabilities into the traditional capacity limit analyses to get a more accurate picture of where rooftop solar installations are likely to increase in Fort Collins and whether our feeders will be able to handle it. These analyses can also help inform policies, including financial incentives, to increase solar in undersubscribed neighborhoods.

If we find that there are likely to be violations, the city can make informed decisions about potential grid upgrades that would increase the capacity limits of the necessary feeders, before potential solar customers are turned away. If we find that there are not likely to be violations, then the city can count on continuing solar adoption to help meet its climate goals.

Now in 2030, instead of turning you away, Fort Collins Utilities gives you the go-ahead to install solar on your home, due in part to our analyses. Happily, you can now reap the benefits of rooftop solar that you’ve seen others experience. Additionally, the city is prepared for your neighbors and others to install rooftop solar. Following our methods, other municipalities have also been able to prevent issues, and in our city and in others, these analyses helped make the solar rollout process smoother. City planners anticipated potential roadblocks and overcame them before they become serious issues, which ultimately helped to speed up the energy transition, to reduce the carbon footprint of our electricity grid — and to bring the benefits of the energy transition to you.

About the Author:

Liz Ross is a PhD candidate in the Applied Social and Health Psychology program, a trainee in the InTERFEWS program at Colorado State University, and a graduate intern at the National Renewable Energy Laboratory. Liz applies social science methods to climate change mitigation and works on projects dealing with just energy transitions and sustainable behavior adoption.


Advanced hosting capacity analysis. (n.d.). from