It may sound like a pipe dream to householders emerging from a winter of punishing bills but the first ever home with no electricity bills has completed its first winter trial.
The striking-looking building in rural Bruetten, in Switzerland's Zurich canton, cost 6.1 million CHF (4.8 million GBP) to build using state of the art energy saving technology.
Now - after enduring their first freezing, wet and foggy Swiss winter - the block's first tenants have revealed they hardly noticed not being wired up to mains electricity at all.
The whole building is covered in hi-tech solar panels with giant energy storage battery cells in the basement that can retain power for three days.
Two water tanks - with a capacity of a quarter million litres - store heat, which is later recycled into the heating system.
Even the still warm bathwater is reused and fed back into the central heating.
First resident Daniel Marty lives there with his girlfriend in one of nine flats and said they hardly noticed the difference.
He said: "The washing machine could not be used at certain times because of the shortages.
"But that happened rarely and I was not affected."
Residents had to consume half the amount of energy of an average Swiss household, dropping to 2,200 kilowatt per hour from 4,400.
But Marty explained: "We did not have to change our lifestyle. The only difference was that we were able to check how much energy we were using."
Experts monitoring the project say they have now learned they need improved ways of storing solar energy.
Joerg Sigrist - whose company Umwelt Arena built the house - said: "The house works and we have discovered possibilities to improve the heat storage.
"In a case of emergency we could have turned off the less important energy users, such as the elevator."
But if new Swiss energy laws are adopted next month (May) what seems cutting edge now may become day to day life.
Switzerland will need to reduce its electricity consumption by 43 percent in the next 18 months.
Sigrist explained: "With this house, we wanted to show what is possible even today."