Amory Lovins last year harvested from his small garden more than 30 pounds of bananas, along with guava, mango, papaya, loquat, passion and other exotic fruit. Nothing remarkable in that, except that the energy analyst and chief scientist of the Rocky Mountain Institute (RMI) does not live in the tropics but in an unheated house 6,500 feet up a mountain near Aspen, Colorado, where the temperature falls to -44C and where last week more than two feet of snow fell in less than 24 hours.

The fruit is grown in a greenhouse that is part of the sprawling, experimental, super-insulated house at Old Snowmass, built 30 years ago for $500,000 (£300,000) and an inspiration for a generation of energy thinkers, designers and sustainable builders. Visited by 100,000 people, it was the archetype for the European Passivhaus movement.

"Heating systems are so 20th century," he says. "We have found you actually save money by not putting in a heating system. It's cheaper. The monitoring system uses more energy than the lights."

On a visit to the Caribbean where the RMI is working with Carbon War Room NGO to help island states wean themselves off expensive diesel-generated electricity, Lovins recalls a visit in the mid-1980s from the originators of the Passivhaus idea, Bo Adamson of Sweden and Wolfgang Feist from Germany. "They realised that you could make heating systems far smaller but they hadn't realised that you could save energy by eliminating the heating kit completely."

Lovins has always maintained that energy conservation not only pays for itself, but that energy-saving technology can lead to higher quality of life at lower cost. He has advised many of the world's largest companies and dozens of countries how to reduce bills with renewables but has also challenged the giant car, aviation and construction industries to rethink the way they operate.

Thirty years since moving to Colorado from Britain, where he was Friends of the Earth's first-ever employee, the 66-year-old sees the energy revolution which he helped kick-start with a series of academic and policy papers now in full swing. "Since 2008, half the world's added electrical generating capacity has been renewable. Non hydro-electric renewables, chiefly wind and solar, were 49% of US and 69% of European capacity added last year.

"In three of the world's top four economies, China, Japan and Germany, there was more generation of electricity from non-hydro renewables than from nuclear in 2012."

Renewables have scaled up incredibly fast, he says. "Worldwide it is faster than mobile phones. More Kenyans now get first electricity now from solar than the grid. China got more generation from wind in 2012 than from nuclear and it added more generation from non-hydro renewable energy than fossil and nuclear combined. It is now the world leader in seven of the 10 renewable energies and wants to be top in all 10. It appears to have added 12GW of photovoltaics in 2012 – that's more than the total that have been installed in the US."

The US, which lagged behind for years, is shifting, too, he says. "The US is a giant laboratory. Different states are going at different speeds. Texas is best for wind, it now gets 10% of its energy from wind because it's good at business; Hawaii is ground zero, with one in 10 households now with a PV system.

"The energy intensity of the US economy has declined 50% in 10 years, mostly because of better design. In 2012 the energy used to make a dollar of GDP went down by 3.4% in one year. We can see a very clear way forward to trebling energy efficiency by 2050."

Most encouraging, he says, is that 14 states for electricity and 20 for natural gas now reward consumers for cutting bills. "That is the reverse of the use of electricity as a commodity. Electricity is an infrastructure, not a commodity. We need to reward the provider to give you lower bills".

Twenty years ago, Lovins proposed what he called the "Hypercar", a hybrid electric/hydrogen-fuelled family vehicle that had only a few parts, was made of lightweight carbon but was stronger than steel, used existing technologies, weighed half a normal car of its size, and could travel the equivalent of 300 miles to the gallon. It was designed to have next to no emissions and, using its batteries, could become a power plant on wheels when parked, eliminating the need for nuclear or coal-power stations.

2014, says Lovins, sees the commercial birth of the Hypercar, with the arrival of the all-carbon electric BMW i-3 family and the 313 miles per gallon Volkswagon XL1 with emissions of just 20g/km. "The car industry is notoriously slow to change," he says, but "you could say the era of the hyper car is starting now."

The most exciting energy conservation advances may be in the way new technologies and business models can be combined, he believes. He was the first to suggest that cars, which are on average used for just an hour a day, be used to generate and store electricity and then be able to despatch it back to the grid.

"Suppose I am a carmaker and I have two identical plug-in cars, one for £5,000 less than the other. Suppose that the car maker can use the battery of the cheaper one to sell to the grid at peak times … in other words a car-maker can profit from your stationary car."

"In the future I see radically cheap renewable energy and storage, new types of battery, super-windows, cheap ways to instal LEDs in large buildings to eliminate wiring, many advances in insulating materials, smart thermostats that learn what comfort you want and buildings that do not need heating or cooling."

But despite all the advances in technology and business models, Lovins weeps for Britain, where he lived for 12 years during and after a spell at Oxford University. He led the successful opposition in the 1970s to stop Rio Tinto digging up Snowdonia with a massive mine.

"Britain's plan for a fleet of new nuclear power stations is … unbelievable," he says. "It is economically daft. The guaranteed price [being offered to French state company EDF] is over seven times the unsubsidised price of new wind in the US, four or five times the unsubsidised price of new solar power in the US. Nuclear prices only go up. Renewable energy prices come down. There is absolutely no business case for nuclear. The British policy has nothing to do with economic or any other rational base for decision making."

In the end, he says, "economics tends to win over stupid policy. The energy revolution is under way but there are decades of playing out to be done. It's both encouraging and frustrating that it's not going faster. This work requires relentless patience."