TGEN vs CLNE

For growth investors, Tecogen Inc.

(TGEN) is the stronger pick with 19. 7% revenue growth year-over-year, versus 2. 2% for Clean Energy Fuels Corp. (CLNE). Analysts rate Tecogen Inc. (TGEN) a "Buy" — based on 4 analyst ratings — the highest consensus in this comparison. The "better buy" depends entirely on your goals: growth investors should weight revenue trajectory, value investors should weight P/E and PEG, and income investors should weight dividend yield and streak.

Over the past 5 years, Tecogen Inc.

(TGEN) delivered a total return of +180. 2%, compared to -73. 8% for Clean Energy Fuels Corp. (CLNE). Over 10 years, the gap is even starker: TGEN returned -3. 2% versus CLNE's -26. 9%. Past returns do not guarantee future results, and the stock with the higher historical return may already have its best growth priced in.

By beta (market sensitivity over 5 years), Clean Energy Fuels Corp.

(CLNE) is the lower-risk stock at 1. 19β versus Tecogen Inc. 's 3. 43β — meaning TGEN is approximately 188% more volatile than CLNE relative to the S&P 500. On balance sheet safety, Tecogen Inc. (TGEN) carries a lower debt/equity ratio of 13% versus 18% for Clean Energy Fuels Corp. — giving it more financial flexibility in a downturn.

By revenue growth (latest reported year), Tecogen Inc.

(TGEN) is pulling ahead at 19. 7% versus 2. 2% for Clean Energy Fuels Corp. (CLNE). On earnings-per-share growth, the picture is similar: Tecogen Inc. grew EPS -57. 9% year-over-year, compared to -173. 0% for Clean Energy Fuels Corp.. Over a 3-year CAGR, TGEN leads at 2. 7% annualised revenue growth. Higher growth typically commands a higher valuation multiple — check whether the premium P/E or P/S is justified by the growth rate using the PEG ratio.

Tecogen Inc.

(TGEN) is the more profitable company, earning -30. 5% net margin versus -52. 3% for Clean Energy Fuels Corp. — meaning it keeps -30. 5% of every revenue dollar as bottom-line profit. Operating margin tells a similar story: CLNE leads at -22. 1% versus -26. 3% for TGEN. At the gross margin level — before operating expenses — TGEN leads at 36. 3%, reflecting greater pricing power or product mix advantage. Stronger margins indicate durable pricing power, lower cost of revenue, or higher mix of software/services. They are one of the clearest signs of business quality.

None of the stocks in this comparison currently pay a material dividend.

All are effectively zero-yield and should be held for capital appreciation rather than income.

For long-horizon retirement investors, Clean Energy Fuels Corp.

(CLNE) is the stronger choice — it scores higher on the combination of lower volatility, dividend reliability, and long-term compounding (low volatility (β 1. 19)). Tecogen Inc. (TGEN) carries a higher beta of 3. 43 — meaning larger drawdowns in market downturns, which matters significantly when you cannot wait years for a recovery. Both have compounded well over 10 years (CLNE: -26. 9%, TGEN: -3. 2%), confirming both are viable long-term holds — but the lower-volatility option typically results in less emotional selling during corrections. Retirement portfolios generally favour predictability over maximum returns. Consult a financial advisor before making allocation decisions.

These companies operate in different sectors (TGEN (Industrials) and CLNE (Energy)), which means they face different economic cycles, regulatory environments, and macro sensitivities — making direct comparison nuanced.

In terms of investment character: TGEN is a small-cap high-growth stock; CLNE is a small-cap quality compounder stock. These fundamental differences mean investors should not choose between them on a single metric — the "better stock" depends entirely on which of these characteristics aligns with your investment strategy.