"We believe if we invest in insulating people's homes, we can get their fuel bills down on a permanent basis," Ms Lucas told BBC Radio 4's Today programme
"It would also get our climate-change emissions down and could create hundreds of thousands of jobs.
"And crucially, for every £1 invested in this programme, it's estimated that £1.27 comes back to the economy in terms of the benefit in jobs and reduction on the NHS bill."
Ms Lucas said the government had "a woeful record on energy insulation", with the installation of energy-efficient measures in UK homes falling by 80% over the last two years.
The Green Party has called for a "progressive alliance" with the SNP, if it has MPs at Westminster in the next Parliament.
Ms Lucas ruled out backing a Conservative government, but said Green MPs could support a minority Labour administration on "a case-by-case basis".
Analysis, by Laura Kuenssberg, Newsnight chief correspondent
The Green Party's manifesto is full of big promises: a pension of more than £300 a week for a couple, renewable energy taking over from fossil fuels, a million new public sector jobs.
But they are having difficulty defending their numbers robustly. They claim they'll raise a massive £30bn extra from clampdowns on tax avoidance; very, very optimistic. And the man behind the manifesto's numbers, Brian Heatley, told me they couldn't really be sure how much their new wealth tax would raise because it hasn't been tried before.
They say they could make up any shortfall by reducing their planned cut to employers' national insurance contributions.
In one sense, refreshingly candid. In another way, extremely problematic for a party that wants to be taken seriously on a tax that they need to raise £20bn.
The Greens also say they would carry on spending more each year than the government gets from revenue. Does that mean deficits for ever? The party won't say.
In other news, Natalie Bennett has told Newsnight they don't want to ban the Grand National after all - more straightforward than working out government spending.
"That would give us a real opportunity to push Labour on the policies we know the public wants and which are at the heart of our manifesto," she said.
"Whether that's scrapping nuclear weapons or reversing the privatisation in our NHS, whether that's returning local schools to local control or bringing rail back into public ownership."
'Scrap road building'
Recently, Ms Bennett said the party's policy of a Citizens' Income of £72 a week for every adult in Britain would feature in the manifesto, but that it would take longer than one parliament for it to be implemented.
The cut in public transport fares would be paid for by scrapping new road-building programmes, while the party is also expected to pledge free social care for the elderly.
At the weekend, Ms Bennett said the 60% top rate of tax would apply to people earning over £150,000 and that it would raise £2bn a year.