The ICO said the fine handed to Home Energy & Lifestyle Management Ltd (Helms) was the largest it has issued for nuisance calls.
It ruled that the Glasgow-based firm breached marketing call regulations with its campaign which "made people's lives a misery".
The ICO said its investigation found that Helms made more than six million calls as part of a massive automated call marketing campaign offering "free" solar panels.
An organisation should have people's permission - which specifically names the company concerned - to make automated calls, but the ICO said it found this was not the case.
In the period from October to December last year, the ICO received 242 complaints about the calls.
One complainant said they had been waiting for news of a terminally ill family member and could not ignore the phone, and felt powerless against the automated calls.
Another said they felt as though their home had been invaded as the answer machine filled up with calls from the company, the ICO said.
The investigation also found that the calls were "misleading" because the solar panels were not necessarily free as implied by the recorded message.
Steve Eckersley, head of enforcement at the ICO, said: "This company's ignorance of the law is beyond belief. It didn't even bother to find out what the rules were and its badly thought-out marketing campaign made people's lives a misery.
"The monetary penalty is for a significant amount because of the clear failings of the company, and the number of people affected by its deliberate and unlawful campaign.
"It should be a warning to other companies to think before they launch into a campaign."
Home Energy & Lifestyle Management told the BBC that the campaign had stopped before the ICO investigation commenced and blamed another company for the issues raised.
In a statement from its lawyer the company told the BBC: "Helms had significant difficulty in fully co-operating with the ICO, owing to the failure of the third-party company to give any information to verify and explain the extent of the calls made."
It said the ICO had "seemingly disregarded" its representations and vowed to appeal, as well as taking action against the other company.
Which? executive director Richard Lloyd said: "A bumper £200,000 fine by the ICO should make nuisance callers sit up and take notice. We now also need to see senior executives held personally accountable if their organisation makes unlawful calls.
"With the Government looking at making caller line ID mandatory for marketing calls and increased action from regulators, telecoms providers must now play their part and use technological fixes to help cut off nuisance calls."
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