Ontario to impose 25% tariff on power to three U.S. states

It helps when you read past the headlines, and read the actual quote from him.

“If these tariffs persist, if the Trump administration follows through on any more tariffs, we will immediately apply a 25 per cent surcharge on the electricity we export,”

Sorry to naysay you here, but one sides import is another's export. Also, the first sentence from the Wikipedia entry on tarrifs.

A tariff is a tax imposed by the government of a country or customs territory, or by a supranational union, on imports or exports of goods.