B.C. New Democrat energy critic John Horgan is warning B.C. residents to brace for what he's calling rate shock under an NDP government when it comes to their electricity bills.

Horgan said recent Hydro documents filed as part of the Crown corporation's environmental plans for its proposed Site C hydroelectric dam reveal financial losses, power surpluses and low prices, all signalling higher Hydro rates for consumers.

He said the Site C environmental impact documents filed last week by Hydro to federal and provincial environmental agencies reveal a huge loss on the horizon.

"Rather than doing what any reasonable person would do, we have instead been buying high and forcing BC Hydro to sell low. The consequences over the life of the next government, if you combine the cost of our liabilities to the cost of the marketplace over the course of the next government, BC Hydro will lose $1 billion," Horgan said.

He says the documents also show Hydro accumulating and forecasting huge power surpluses, which suggests Site C doesn't need to proceed immediately.

Horgan says if the NDP wins the May election, British Columbians can expect delays in Site C for at least two years and perhaps more, but he used the word rate shock when asked how Hydro's fiscal situation will impact ratepayers.

Energy Minister Rich Coleman said that the BC Hydro situationis is one of short-term pain for long-term gain.

"There is a deficit in the price during periods of time of a long-term contract, but that's no different than when W.A.C. Bennett built the dams. He built dams that were more expensive to power back in the 50s and 60s, but long term, over the term of the dams, they've proven to be a really good economic advantage for B.C. to keep power rates down for people."

The NDP says it wants The B.C. Utilities Commission to take an independent look at the situation.

With files from the CBC's Stephen Smart