Hey everyone! I have a flat-roof property where I installed a large solar array, around 30kW, but SDG&E (the utility in San Diego) only has a 26kVA transformer serving several homes. I've read mixed opinions – some say that my solar production decreases the load on the transformer, while others suggest it could actually increase stress and risk damaging it. I'm curious if adding more solar panels might cause any issues. Additionally, how should I best use my excess production given that SDG&E's rates are high? What would happen if the transformer failed? I'm looking for solid technical insights, not just opinions. Thanks!
3 Answers
It's definitely a concern, especially since states like Hawaii have stopped compensating for solar production due to high installations. The risk increases when you have multiple homes backfeeding energy, which can indeed blow the transformer. If it goes out, power will be lost for your entire neighborhood, and utilities might not take kindly to exceeding your permitted limits.
From what I've read, transformers can usually handle more power than their rated capacity, especially in areas with steady wind that keeps them cool. However, if too many neighbors start generating extra power, it might strain the transformer. If it fails, everyone on that transformer loses power, including those with solar setups. Utilities often aren't designed to handle every house backfeeding power at once, so caution is key!
Yes, it's possible to damage a transformer if you exceed its capacity with your solar array. The load on the transformer actually reflects the difference between production and consumption. If your solar input is high and consumption is low, the transformer can overheat and fail. Just be cautious because if you don’t have the proper permits, you might be financially responsible for any damages. It’s best to monitor your system and think about smart load management to optimize your energy use.
Totally agree! Also, consider looking into smart meters that can help limit your system’s exported power so it stays within safe levels. It’ll help you avoid unnecessary risks.

Right! And outages will depend on the specific utility practices in your area, which might not be up to date with all the new solar installations.