There is no national answer
Whether you need permission depends on your state, your utility and sometimes your city. The same kit can be explicitly legal in one state and require a full interconnection agreement a border away.
This is general information, not legal or electrical advice. Rules are changing quickly. Confirm with your own utility and local code official before installing anything that connects to your home wiring.
What Utah changed
Utah passed legislation explicitly permitting small plug-in solar systems without the formal interconnection process a full rooftop array requires. It was the first US state to carve out that exemption, and it is the template other states are looking at.
What to ask your utility
- Do you permit small plug-in or balcony solar systems?
- Is there a wattage threshold below which no interconnection agreement is needed?
- Do I need to notify you, even if no agreement is required?
- Does my meter handle back-feed without penalising me?
Get the answer in writing. Front-line staff are frequently unfamiliar with the category and may guess.
The meter question
Older mechanical meters can spin backwards when power flows the other way, which utilities do not like. Most modern smart meters simply record it. If you are on an old meter it is worth establishing what happens before you generate anything.
HOAs and landlords
Separate from the legal position entirely. An HOA can have views on what is visible from the street even where the state permits the equipment. See solar for renters for how to approach that conversation.