1 n. — abbreviation
hydroelectric power; also hydro power.
Type: 5. Frequency — Hydro is a clipping of hydroelectricity, a type of power that is generated by converting the force of flowing water into electricity. According to 2012 statistics from Natural Resources Canada, 59% of Canada's electric power supply comes from hydro power, making the country the "third largest producer of hydroelectricity in the world" (see NRCan reference). The US, in comparison, derives most of its electric power from fossil fuels (67%) and only 7% from hydro power (see EIA reference). Boberg (2010: 121) marks hydro as a regionalism, noting that it is primarily used in British Columbia, Manitoba, Ontario and Quebec, the provinces that contain hydroelectric power plants. The earliest Canadian attestation of the term appears in the early 20th century (see the 1916 quotation), a period when hydroelectric power generation underwent significant expansion and sites began appearing across the nation (Canadian Encyclopedia, s.v. "hydroelectricity"). Internet search results indicate the term is most prevalent in Canada (see Chart 1) and that the term is used throughout the country (see Chart 2).
See also COD-2, s.v. "hydro" (1), which is marked "Cdn", ITP Nelson, s.v. "hydro" (1), which is marked "Canadian", Gage-1, s.v. "hydro" (1), which is marked "Cdn", and W-3, s.v. "1hydro" (2a), which is marked "chiefly Canada".
See also: Hydro Hydro-Electric
- 1911  Hon. Adam Beck turned on the Hydro power in the home of his birth here to-night, in the presence of almost the entire population of the thriving village. Baden is the first of the smaller towns and villages to use Niagara power, and this evening, the streets were illuminated for the first time with electricity generated at the falls. 
- 1916  The product of Niagara, according to [Sir Adam] Beck, is Hydro-Electric--familiarly abbreviated to Hydro [...]
- 1952  The cities of Alberta, also, have good sources of power, including coal, natural gas and hydro.
- 1962  [...] due to cheap hydro power, the Niagara Peninsula became one of the most industrialized parts of Canada.
- 1962  The advice to Nova Scotia's two major power companies [was] forget about hydro development.
- 1964  The B.C. government has introduced safety valve legislation in case its hydro laws are repudiated by the courts.
- 1979  In our fisheries, our oil and gas on the offshore, and our hydro and mineral potential in Labrador, we see rich possibilities for the future.
- 2009  It's not a perfect marker for industrial activity, because some industry runs off nuclear and hydro power, especially in Central Canada. 
- 2015  The publicly traded company, which grew from a Nova Scotia base, was under government pressure to move from high reliance on coal-fired generation to clean energy like wind power and hydro. 
2 n.
electricity as a utility.
Type: 3. Semantic Change — Hydro power has become the most common form of electricity in some provinces, distributed by commissions and corporations like Hydro-Québec, Hydro One in Ontario, and BC Hydro. The term hydro consequently experienced a semantic shift from describing water-generated power to household power, however generated. It thus became common to refer to anything associated with the utility as hydro, i.e. hydro bill (see the 1949 quotation). This can lead to confusion for those who associate the hydro prefix exclusively with water and confuse their hydro bill -- their bill for electricity -- with their water bill.
See also COD-2, s.v. "hydro" (4), which is marked "Cdn", ITP Nelson, s.v. "hydro" (2), which is marked "Canadian", Gage-1, s.v. "hydro" (2), which is marked "Cdn", and OED-3, s.v. "hydro" (n.2), which is described as being used in Canada.
- 1939  "[...] the telephone and hydro wires are down."
- 1942  The sparkle left the streets of cities and towns in Ontario and Quebec Sunday night as new dim out regulations went into force and centres turned out all but essential lights in an effort to conserve hydro.
- 1946  Food, hydro, water, telephone for September, forty dollars.
- 1949  Claude wrote out the address [...] on the envelope of the hydro bill he'd forgotten to pay.
- 1958  What about the hydro we've been waiting for, and the washing machine and stove and frigidaire to go with it?
- 1964  Added to these costs would be a minimum of $650 to $700 for winter berths, hydro and water service [...]
- 1973  With hydro rates already increasing, with fuel oil and gas rates almost certain to go up as a result of interprovincial feuding over energy rates, withdrawal of the proposed sales tax on light and heat is only good sense.
- 1989  Problem: I rent an old house that has no insulation. It is heated with electricity, and my annual hydro bill last year was $2300. But the rent is very low, which is why I am staying here. I would like to know if it would pay me to add some insulation, and if so, where. 
- 2000  It tells the tale of a pair of growers and their experiences producing cheap hydro set-ups using household and found materials.
- 2015  The new tenants - aided by government agencies - will pay $1,095 per month for a two-bedroom unit and $1,195 for a three-bedroom suite, with hydro included. 
Images:
Chart 1: Internet Domain Search, 9 Oct. 2014
Chart 2: Regional Domain Search, 26 Jun. 2016