Thank you to everyone who has commented.
The short follow up:
A question: If this bill is left unpaid and sent to collection could the solar company get a lien on my father's house for the amount owed?
The amount being billed is a percentage of the total cost of installation. It is a 10% figure billable if the contract is broken. I did not see any evidence that the house was altered. I think a crew was dispatched to his home and they were only preparing to begin the installation. If they solar company sued him and he had to appear in court the judge would see his mentality. It might take medical testimony after examinations to legally concrete but the judge would get a sense for his frailty and fuzzymindedness. By the time this got that far he might be too ill. He does have cancer. I am not paying the solar company any money. I like the idea of a pithy letter of refusal from a lawyer.
The long follow up, if interested:
Regarding the contract, there was a window of wiggle room but it was too late when we discovered the crew working at my father's house.
The solar company manager is unsympathetic to the idea that one of his salesmen took advantage of an old man.
Although there may be nothing illegal in what they did the solar company is not "blameless." Take a look at what the benefits are for investing in solar. Of those what would an 86 year old man gain from adding solar to his house? He certainly would not live long enough to see any savings in energy expenses compared to what he paid to have it installed. The salesman only cared about closing a deal. The salesman knew he was encouraging a frail old man to invest a lot of money in something and he would never reap the benefits being presented to him. (Someone might call fowl for using loaded language but these words describe the situation. Consider this whole story hypothetical if you need proof).
Some businesses exist on their skill at taking advantage of the elderly. People have an innate need to experience closure. When you start to lose your health there is a growing list of obstacles in the way of navigating through life. When you start to lose your memory you may not be able to see projects and tasks through to completion. Businesses and charities understand that they can tap into this by providing the easiest method of making a purchase or donation. When the elderly person makes a purchase or donation they are setting out to accomplish a task. They are sold on the idea that a purchase will be good for them before making the sale. A donation is a good thing. When completed, they receive a product or a token of gratitude for their effort. They feel like they have some purpose to their life again.
All day on typical TV stations catering to the elderly are commercials making it easy to purchase a product. My father gets stacks of mail soliciting donations. Business pitch their worthless junk as collectibles. My father was in the Marines. He gets tons of junk mail selling tokens of his veteran status.
My father used to build models. He stopped because he could no longer focus on the task and follow the instructions. One of his replacement activities is to go grocery shopping. He doesn't look for what he is out of. He just walks through the store buying this and that. He comes home having accomplished something. His refrigerator is so full of groceries I have to pack up a load each week to make room for the next round. At least he is getting something out of this even if it is not nourishment.
Elderly people are lonely. Yet they frequently want independence. My father never used to answer his front door. Now he will for something to do. I put up a No Soliciting sign because local homeless people had spread word that he would donate to anything. They come to his door pretending to be a charity. He took the sign down.
When I stopped him from driving he did everything he could to get around it. First he agreed but lied. I had to lock his car up with antitheft devices. He paid a locksmith to unlock and re-key his car. I disabled the car deflating tires and disconnecting cables. He figured out how to get it running. I did not want to make it so difficult that even I could not get it running if I had to but eventually I had to exceed his ability to figure it out. He finally gave up. It will take a mechanic to get it running as it was easier to disable than it will be to put it back together.
He may not remember everything when he needs or wants to but he remembers how to be stubborn.
It is easier said than done placing people in a better situation. He does not want to live in a retirement home. He does not want anyone living with him that would not be a coconspirator who would help him drive or buy whatever he wanted. He was brutal to the nurses when he was in the hospital a few years ago. Even when he was at his best he was a rather unsociable territorial grump. He likes who and what he likes and complains about what he doesn't like. Locating a caretaker he will accept and who will accept him is a challenge.
I am taking it in steps. He wasn't keeping up with his payments and damaged his credit before I realized it and could get him to a point of acknowledging it and allowing me to take over for him. The solar company will not see a dollar of that money. I'd like to report this incident to the Attorney General's office or something so it is on record at least.
Technically, my father may not meet the legal definition of mentally incompetent and I don't want to see him have to prove that for this solar company. He is a frail old man who was sold something very expensive he did not need and could not benefit from. I imagined a judge admonishing this business owner for unethical business practices preying on the weak.
Thank you all again.