Around 5,000 soon-to-be recipients of roof-mounted solar panels in Northampton's council houses will only see the benefits if they use energy during the day, a social housing chief has admitted.
Thousands of social homes are set to be with a free solar panel as part of a partnership with a private energy firm and management organisation Northampton Partnership Homes (NPH).
But recipients will have to change their energy using habits to reap the benefits from the panels - which council papers claimed would save up to £200 a year.
NPH Chief executive Mike Kay says the panels will not store any "excess energy" - but will supply a home with free electricity "when it's light."
He said: "One of the most important things a lot people don't realise is how you adapt your lifestyle.
"If you are putting your washing machine on, do it when it's generating electricity it's free electricity."
And of those who work during the daylight hours in winter, he said: "Most people leave when it's between 7.30 and 8 in the morning, by which time it's light anyway.
"It is about getting into the habit of putting your appliances on then."
If the panels are generating excess electricity, the surplus is then sold to the national grid, with the proceeds going to the private energy firm Saliis
When the Chron reported that the solar panel scheme was given the go-ahead on February 7, a handful of people got in touch to say that their roof-mounted panels had delivered little or no reduction in their bill.
NPH completed an installation on 1,400 Northampton social homes in January last year, though some panels were not connected to the National Grid until autumn.
But Mr Kay believes that in most cases this because a household's energy consumption has gone up as a result of having a panel installed.
"I have seen some people in bigger houses reduce their bill by £00-£400 a year as a result.
"I have seen others whose bills haven't reduced but their consumption has gone up. that means they could be generating more heat, more light that they weren't before. That has to be good for them.
"This could go some way in alleviating fuel poverty."
It is not yet known which part of Northampton will begin receiving the panels first. But Mr Kay said contractors will also leaflet areas where they are completing installations there - offering private homeowners the chance to have a roof panel fitted as well.
"The contractor wants economies of scale," Mr Kay added. "They don't just want to do three houses on this street and then move on to another. If you are interested you can email them your details."
The installations are set to start in spring and be completed in around a year's time. Residents will also have the choice of opting out.