Homeowners in Vancouver planning to build laneway housing units in their backyards are experiencing sticker-shock when they apply to have electrical power hooked-up to the new units, according to one designer.

Bryn Davidson, who runs Lanefab Custom Homes, said he was originally told by city staff it would cost just a few hundred dollars to hook up power to the new backyard rental units.

"We were told from the city and other people that we would be able to just run off of an upgrade to the main house for about $500," said Davidson.

But now that his clients are going ahead with their projects, BC Hydro has revealed the price for hook-ups will be up to $20,000 for some homeowners.

"Through the process of dealing with these first ones, we were originally told [by BC Hydro] it would be between $20,000 and $30,000, and now they're saying between $8,000 and $20,000," said Davidson.

BC Hydro was not available for comment early Monday morning, but Davidson said the power company said the overhead power lines are at capacity, so the new lines will have to be run underground.

One of Davidson's clients, Agnus Mendoza, said she can't believe staff at BC Hydro appeared to be so unprepared for the new homes and were not more upfront about the potential costs.

Mendoza says she's already spent more than $4,000 on development fees and was hoping to break ground on her unit this week before learning of expensive hook-up fee.

"They should have been more proactive and said, 'Look guys, the city is planning this. What are we going to do? What should our policy be?'" said Mendoza.

In July, Vancouver City Council approved the building of new laneway housing units or the conversion of existing garages into housing in an effort to increase density in urban areas and allow homeowners to generate more rental income.

Estimates to build a typical 500-square-foot laneway housing unit range from about $110,000 to more than $200,000, plus about $40,000 for water and sewer hook-ups, and now it looks like homeowners will have to foot the bill for the new the BC Hydro charges as well, said Davidson.