Email Sherry Listgarten About this blog: Although climate change has a huge impact on the planet, it is still an abstract concept for many of us. This needs to change. I hope readers of this blog can better understand how our climate evolves... (more) About this blog: Climate change, although it has a huge impact on the planet, is still an abstraction for many of us The concept. This needs to change. I hope that readers of this blog will have a better understanding of how our climate has evolved and how they want to respond, and will feel comfortable asking questions and exchanging opinions on this topic. It is important that we reach a consensus on the impact of basic science and climate change in order to understand our future actions and policy choices. My background is not climate science, and I am not even particularly green; I hope this helps make this blog more relevant. I studied mathematics and neurobiology on the east coast, and then moved here in 1987 to study as a graduate student in computer science. After working in the technology industry for about 25 years, I retired a few years ago to better align my time with my priorities. I like spending time outdoors and deeply feel our responsibility to this incredible planet we call home. (hide)

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Excellent summary! There is only one comment that the "full" panel may have one or more circuit breakers, which no longer power any appliances in the home, especially if it has been remodeled before. I have an orphan 20A circuit breaker, which controls nothing, and a 220v circuit in the garage that used to power the dryer. This task is now served by the circuit in the subpanel, but if I don't know, I might think the panel is full.

Excellent articles/blogs, most readers can easily understand. Sometimes your other posts with all the graphs and statistics are a bit difficult for fools like me to handle.

Great article. What is not mentioned is the consideration that homeowners want to add solar panels or battery storage, which may be worth writing a separate blog. The rules for adding solar circuit breakers are different from the rules that apply to load circuit breakers, because solar energy (and battery storage) powers the home instead of consuming it. Based on my experience as a solar installer, I found that adding solar energy to homes with electrical panels rated at 100A (or lower) limits the size of the solar installation. Many families have been told to upgrade their services to 200A or higher to support larger solar installations. This can be expensive, especially if the home has underground services. I want to point out that upgrading service lines is not always necessary. There are new electrical panels for connecting solar energy. For example, a panel with a 125A main circuit breaker and a 225A rated bus can support larger solar installations without the need for utility companies to upgrade service lines to the home. If your existing panels do not have sufficient busbar ratings for photovoltaic systems greater than 5kW, and you can use more space for the circuit breaker, please consult a qualified electrician to find out what options are available for you in addition to service upgrades .

good article. It is worth noting that if the house has solar energy (or other renewable energy), the optional method 220.87 cannot be used.

These comments are great, thank you! @Eric, thanks, I will add this comment to the post. @Marc, thank you for letting me/readers know about this new type of panel, it makes a lot of sense. @Eeyore, great point. Ideally, electrical unions disconnect and mark isolated circuits, at least those without sockets or equivalent circuits. When I wrote this article, I discovered that my parents had two (large) circuit breakers on a separate panel labeled "Scope". The new series replaced the old series, but electricians never disabled the old circuit or changed the label. Oops. @Lyle, glad you like this article! Generally speaking, it is difficult for me to know what level of detail readers like. As you have noticed, I tend to include data (especially visual effects) because I think it is important for people to be able to see the facts/data behind the text. Sometimes even if you don’t fully understand the picture, it’s fun to look at the picture. But in the end I can never be sure which posts will be popular. I once wrote an article called "Pipelines, Power Lines, and Expropriation Fields" and I thought it had almost no readers (has such a title?), but I was totally wrong. My daughter made fun of me saying that "your electric panel" is also a terrible title. Well, at least it is readable! Thanks for your comment :)

@Eric, thank you for pointing out the new ban in the latest code cycle. I saw that a new exception was just added in the recent code cycle that prohibits solar customers from using section 220.87 to determine the adequacy of panels for new planned equipment. By completely banning solar customers from using the 220.87 method, this seems to over-limit the problem, because it can be said that 80% of the solar feed circuit breaker rating will be added to 125% of the historical load, which will get the panel load to reflect the code Worst-case scenario allowed. For example, a person with a 100A panel and a 4 kW AC output inverter and an 8 kW historical maximum 15-minute (net) load will be allowed to add a 10 kW additional equipment nameplate load. (24-4-10) (24 kW panel capacity-4 kW inverter maximum output-8 kW maximum load X 1.25 factor) In order to solve climate change, we need to make it easy to do the right things.

Thank you very much for this series and previous posts, such as the installation of heat pump water heaters. It is nice to see real-world examples and understand important but rarely mentioned issues, such as the calculations used to determine the simultaneous load on the panel.

@Mondoman: I am glad it helps! I have been using this information to fill out my HPWH license. It's so fun to watch the electric board. By the way, thanks to Tom Kabat of Menlo Park, he has been taking the lead in pointing out the surprising flexibility and capacity of our switchboards.

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