In a savings market where the average no-notice account available on the high street pays a measly 0.66%, a cash ISA offers an average of 1.7%, and inflation is above 2%, investors are being forced to consider alternative forms of income.
So the new wave of renewable energy investors are not necessarily environmentally-motivated individuals, keen to put their money where their mouths are. They are as likely to be neutral on the subject of climate change as ardent believers. They might not even like the look of wind farms.
The rise of the retail investor has not come a moment too soon. Returns from renewable energy projects have been falling as subsidies have come down, so the VCs and private equity managers that were so keen on throwing everything into renewables seven years ago are no longer in the market. They don't get out of bed for less than 15%!
This has left renewable energy developers, and institutional investors looking to refinance existing projects, in limbo. And while bank funding might be an option, traditional lenders often have strict criteria on the size and type of projects they are willing to lend to, and interest rates may be prohibitive. Enter retail investors, who are quite happy to accept a return of 6% as long as the risk is commensurate.
And renewable energy projects are appealing. They offer a relatively predictable flow of revenue, partly from electricity prices and partly from subsidies, which rises in-line with inflation. Running costs are low: it's the installation, not the operation, which costs. Demand for clean energy is only going one way. And that's not to mention the availability of direct investments in projects - without the intermediation of costly fund managers and IFAs.
Developers and asset managers have not been slow to wake up to this potential. Foresight Group recently raised £150 million from investors, including retail investors who, for a minimum of £1,000 each, could earn a 6% ISA-able target annual return from their share of eight of the UK's biggest solar parks.
July saw a flurry: the Renewable Infrastructure Group raised £300 million, Greencoat Wind £260 million and Bluefield Solar £130 million from public markets. Infinis, the renewable energy arm of Guy Hands' Terra Firma private equity group, is planning a flotation this month (November), which could be valued at up to £1.5 billion. If this goes ahead as proposed, more than £2 billion of renewable energy will have become available in 2013 to anyone buying shares on the stock market by Christmas.
That represents about one fifth of the £10 billion total capital investment in the Power and Gas sector in 2011, according to Energy UK figures; and a third of the total invested in renewables in the UK in 2012, according to research from Pew Charitable Trusts, which put the total ploughed into renewables last year at £5.9 billion.
Then there are the smaller scale bonds that have appeared - a retail bond from Good Energy paying 7.25% over four years just smashed its £15 million upper target three weeks early. Another similar offer - Secured Energy Bonds, which are still available, pay a slightly lower 6.5%, but have a shorter three-year term. A lesser known developer called A Shade Greener is also punting a £10 million bond. Meanwhile, Ecotricity is rumoured to be considering another after its successful Eco Bonds raises in 2010.
Next are crowd-funded renewables projects, which are available from as little as £5. The only provider of these currently is Abundance Generation, which is authorised by the Financial Conduct Authority. It has raised £3.5m for various projects since its first raise in 2012 and currently has a solar project on school and nursery roofs in Nottinghamshire open for investment.
The contribution of community co-operatives is another growing force. Community renewables organisations such as Pure Leapfrog long for the UK to replicate the success of Germany and Denmark, where people-owned power is mainstream.
And although community renewables are still a tiny part of UK energy generation, the sector could grow to 89 times its current size, according to a recent report by Respublica, the think tank. The main barrier to growth is the human capital involved in getting the projects off the ground. Every renewables venture needs a committed, clever and experienced pool of people with different skills to develop them and raise the finance.
The sector also enjoys strong support from politicians. When Greg Barker MP bangs the drum for the "big 60,000 replacing the Big Six", this is what he is talking about. Ordinary people have the power to shatter the traditional energy market, creating competition in the generation of clean energy and effectively owning their own supply - good for the planet and for energy security.
We could be much less dependent on foreign energy sources if our gas is replaced by wood heat from a community boiler and our electricity comes from a wind turbine at the end of the road. In the long term, a greater proportion of renewables and a falling proportion of fossil fuel generation will have a downward impact on household bills. And of course, there's the Return on Investment to be made: a potential profit to rival comparable alternative investments, such as buy to let.
Of course there are risks, and the amount of risk and its nature depends on the individual product or project an investor is looking at. But roughly: if it hasn't been built yet it is more risky; if it is unregulated it is more risky; and if the developer is inexperienced it is more risky.
As with any type of investment, you could lose all your capital. Products with a longer term bear greater risk as your capital is tied up for longer. Liquidity may be an issue if you are likely to need to unlock the money before the end of the term. If you invest now in something that lasts for 20 years, then inflation falls and interest rates rocket, the return you receive might start to look less appealing and you might struggle to find a buyer if your investment is not a publicly-traded stock.
However economic forecasters are not expecting either of these things to happen in the near term. The sector (and people in it) is approaching maturity. Technology is advancing rapidly. And the financiers structuring the deals that are cropping up can tell the difference between a solid investment and one that should never come to market.
As my boss Julia puts it: "The bottom line is that UK consumers, are ready for green energy and willing to invest in it, whereas the Big Six are dragging their heels on investing in a sustainable energy future for the UK, because they have so much invested in the past. Let's leave them to it and create our own energy companies!"
Rebecca O'Connor is editor for Trillion Fund, the renewable energy investment platform.
