Hydro-electric dams or GCHP's - which one has better return on investment?

The Nelson River drains an area of 344,500 square miles (892,300 square kilometers) in the Canadian Prairies. Manitoba Hydro has built a number of dams on the river and has proposed to build several more over the next 10 years. One of the next dams that is proposed is called the Keeyask Dam. It will produce 695 mW of power and is projected to cost $6.2 billion. That's a capital investment of $8,920 for each kW of power it will produce. Let's compare this to a GCHP system in a typical home.

About 10,000 residential GCHP systems have been installed in Manitoba since the early 1980's...more heat pumps per capita than any other Canadian province. The average residential heat pump system in a typical Manitoba home costs about $25,000 to install. 

According to Manitoba Hydro, there are about 127,000 electrically heated homes in the Province. If a home is converted from electric resistance heating to a GCHP system, peak electrical demand will drop approximately 7.5 kW. If all of the electrically heated homes were converted to a GCHP system, it would reduce peak electrical demand in the Province by about 952 mW. That's 257 mW more power than will be produced by the proposed Keeyask hydro-electric dam. And guess what...it would cost less to convert the 127,000 homes to geo than to build the dam. About $3.0 billion less, for 257 more mW.

And what makes it even more interesting, MB Hydro would not even have to pay to convert the homes. By simply financing the cost of the installations for the homeowners they would reduce the homeowners electricity bills enough to pay for the installations and still have some money left over. So what makes more sense? Build a hydro-electric dam, with all the environmental issues, at a cost of $8,900 / kW, or install GCHP systems at a cost of $3,300 / kW to reduce the use of electricity. The kWh that is produced by the dam can be sold outside the province to boost the economy...so can the kWh that isn't used in the Pr