As far as we know, there's no source of infinite energy.

If you mean "lots of energy", well, depends upon your perspective. By historical standards, you have incredible amounts of energy available at a very cheap price.

One article I like highlights what light has cost. A snippet:

https://bigthink.com/the-past/genius-and-blood-how-cheap-light-transformed-civilization/

We have forgotten how unrelentingly dark the pre-industrial world was. Switch on a nightstand lamp or kitchen light, and you instantly and effortlessly summon into existence more illumination than was available to entire pre-industrial households. Artificial light has historically been the expensive privilege of the wealthy and powerful, while simultaneously being laborious and dirty to produce and maintain, and extremely limited in availability and quality for nearly everyone — but most especially for the world’s poor, which until industrialization was basically everyone. 

It is difficult to fathom just how expensive light was in the pre-industrial world. In what is now the United Kingdom, the price, adjusted for inflation, per million-lumen hours of artificial light was >£40,000 (or roughly $50,000 USD) in 1302 CE. This is the cost-to-light output equivalent to running ten modern 13W LED bulbs for just 7 hours.

While a home lit exclusively with candles may well appear a mark of poverty today, in the 1300s, it was a sign of significant wealth. Good candles made of bees’ wax provided the best light for the time, but their production required expensive materials and specialist skills. A limited supply of natural bees’ wax and laborious artisan manufacturing kept good candles out of the reach of all but the wealthiest individuals. The extreme cost of artificial light was, first and foremost, a technical problem. The demand for a bright, clean-burning illuminant was considerable; however, no one had managed to develop a technology that would allow a practical way of producing it inexpensively and at scale.

The quality, brilliance, and cost of artificial light had remained fundamentally unchanged for thousands of years. Prior to industrialization, artificial light was not only dim, dirty, and dangerous but also a cripplingly expensive time-cost in human labor. Matt Ridley summarized the problem most persuasively in his book The Rational Optimist: How Prosperity Evolves:

Ask how much artificial light you can earn with an hour of work at the average wage. The amount has increased from 24 lumen-hours in 1750 BC (sesame oil lamp) to 186 in 1800 (tallow candle) to 4,400 in 1880 (kerosene lamp) to 531,000 in 1950 (incandescent light bulb) to 8.4 million lumen-hours today (compact fluorescent bulb). Put it another way, an hour of work today earns you 300 days’ worth of reading light; an hour of work in 1800 earned you ten minutes of reading light.

We've very quickly become accustomed to our fabulous wealth compared to that of our ancestors, though, and now think of this as nothing.