Mainspring IPO: Investment Opportunities & Pre-IPO Valuations

Company details

Mainspring is developing a new approach to generating clean, resilient, affordable electricity. Their research into high-efficiency methods of converting fuel to electricity led to the development and prototype of their first linear generator. This company was founded by John Connolly and Marshall Micheals in 1996 and is headquartered in Cambridge, MA.

mainspringenergy.com

Sector

Energy

Subsector

Clean Energy

Founded

2010

Headquarters

Menlo Park, CA, United States

Forge Price ¹

Price not yet available

Post-Money Valuation ³

$973.71MM

Total Funding

$803.94MM

LFR Price per Share

$xx.xx

Last Funding Share Class

Series F

Learn more about Mainspring

To invest in Mainspring pre-IPO

Can you invest in Mainspring pre-IPO?

Mainspring is a privately held company and is not publicly traded, therefore investing in Mainspring pre-IPO is only available to accredited investors. If you meet the accreditation criteria, you can learn more about Forge’s Secondary Marketplace and how to invest in private companies before their potential IPO. If you are not accredited, find out how to begin the process and qualify for new investment opportunities.

Can you sell shares of Mainspring before it goes public?

You can seek to sell your shares in Mainspring while it remains private. If you are considering selling, you can register today for free to get started. Once registered, a Private Market Specialist will guide you through any questions you might have. You may also continue to browse through our resources to help you understand the implications and procedures involved in selling your private market shares.

What is the pre-IPO value of my Mainspring shares?

To determine the value of your Mainspring shares, create a free account to gain access to Forge’s platform. In addition to the Forge Price, Forge Markets contains pricing information for hundreds of pre-IPO companies such as Last Closed Trade Price. A Private Market Specialist will also be available to assist you with any inquiries related to your Mainspring shares. You can also learn more about how to sell your private shares before getting started.

Is Mainspring a publicly traded company?

If you are interested in buying or selling private company shares, you can register with Forge today for free to explore your options. Registering gives you access to one of our Private Market Specialists who can guide you through the process of buying or selling. Learn more about how Forge might help you buy pre-IPO shares or sell pre-IPO shares.

To learn more about Mainspring potential IPO

Will Mainspring go IPO?

Mainspring has not yet filed for an IPO. However, it’s important to note that IPOs are not the sole avenue for a private company to transition to public trading. Private companies can also go public through alternative methods such as but limited to Special Purpose Acquisition Companies (SPACs), direct listings, or mergers and acquisitions. Find out which companies are eyeing an IPO on our Tech IPO Calendar 2025.

What is Mainspring’s IPO price?

The Mainspring IPO price does not exist at this time, as Mainspring is still a private company and has not yet conducted an IPO. To explore secondary market data and access private market pricing details and data that may be related to Mainspring register for Forge Markets, today.

When was Mainspring founded?

Mainspring was founded in 2010.

What is Mainspring funding to date?

Mainspring has raised $803.94MM to date.

Mainspring funding rounds and valuation

Funding history chart

Funding round details

	Funding Date	Share Class	Amount Raised	Price per Share	Post-Money Valuation	Key Investors
	04/14/2025	Series F	$229.38MM	$xx.xx	$973.71MM	Amazon, Dcvc, Gates Frontier, General Catalyst, Khosla Ventures, Lgt Group, Lightrock, Marunouchi Innovation Partners, M&G Investments, Pictet, Temasek
Price per Share $xx.xx Shares Outstanding 61,651,237 Liquidation Pref Order 1 Liquidation Pref As Multiplier 1.0x Conversion Ratio 1.0x Dividend Rate 8.0% Cumulative Non-cumulative Participating Non-participating Participation Cap -- Key Investors Amazon, Dcvc, Gates Frontier, General Catalyst, Khosla Ventures, Lgt Group, Lightrock, Marunouchi Innovation Partners, M&G Investments, Pictet, Temasek
	04/14/2025	Series F-1	$28.62MM	$xx.xx	$973.71MM	Amazon, Dcvc, Gates Frontier, General Catalyst, Khosla Ventures, Lgt Group, Lightrock, Marunouchi Innovation Partners, M&G Investments, Pictet, Temasek
Price per Share $xx.xx Shares Outstanding 9,615,458 Liquidation Pref Order 1 Liquidation Pref As Multiplier 1.0x Conversion Ratio 1.0x Dividend Rate 8.0% Cumulative Non-cumulative Participating Non-participating Participation Cap -- Key Investors Amazon, Dcvc, Gates Frontier, General Catalyst, Khosla Ventures, Lgt Group, Lightrock, Marunouchi Innovation Partners, M&G Investments, Pictet, Temasek
	09/21/2022	Series E	$284.47MM	$xx.xx	$1.04B	Bill Gates, Cpp Investments, Fidelity, Fine Structure Ventures, Hanwha Power Systems, Khosla Ventures, Lightrock, Lineage Ventures, Princeville Capital, Shell Ventures
Price per Share $xx.xx Shares Outstanding 35,251,855 Liquidation Pref Order 2 Liquidation Pref As Multiplier 1.0x Conversion Ratio 1.2x Dividend Rate 8.0% Cumulative Non-cumulative Participating Non-participating Participation Cap -- Key Investors Bill Gates, Cpp Investments, Fidelity, Fine Structure Ventures, Hanwha Power Systems, Khosla Ventures, Lightrock, Lineage Ventures, Princeville Capital, Shell Ventures
	09/21/2022	Series E-1	$18.91MM	$xx.xx	$1.04B	Bill Gates, Cpp Investments, Fidelity, Fine Structure Ventures, Hanwha Power Systems, Khosla Ventures, Lightrock, Lineage Ventures, Princeville Capital, Shell Ventures
Price per Share $xx.xx Shares Outstanding 2,467,100 Liquidation Pref Order 2 Liquidation Pref As Multiplier 1.0x Conversion Ratio 1.2x Dividend Rate 8.0% Cumulative Non-cumulative Participating Non-participating Participation Cap -- Key Investors Bill Gates, Cpp Investments, Fidelity, Fine Structure Ventures, Hanwha Power Systems, Khosla Ventures, Lightrock, Lineage Ventures, Princeville Capital, Shell Ventures
	05/04/2021	Series D	$108.35MM	$xx.xx	$440.31MM	40 North Ventures, Aep, Bill Gates, Chevron Technology Ventures, Clearsky, Devonshire Investors, Equinor, Kck, Khosla Ventures, Princeville Capital
Price per Share $xx.xx Shares Outstanding 20,055,578 Liquidation Pref Order 3 Liquidation Pref As Multiplier 1.0x Conversion Ratio 1.1x Dividend Rate 8.0% Cumulative Non-cumulative Participating Non-participating Participation Cap -- Key Investors 40 North Ventures, Aep, Bill Gates, Chevron Technology Ventures, Clearsky, Devonshire Investors, Equinor, Kck, Khosla Ventures, Princeville Capital
	01/24/2018	Series C	$84.3MM	$xx.xx	$245.46MM	American Electric Power, Bill Gates, Centrica Innovations, Kck, Khosla Ventures, Louis M. Bacon, Statoil Energy Ventures
Price per Share $xx.xx Shares Outstanding 19,546,914 Liquidation Pref Order 4 Liquidation Pref As Multiplier 1.0x Conversion Ratio 1.1x Dividend Rate 8.0% Cumulative Non-cumulative Participating Non-participating Participation Cap -- Key Investors American Electric Power, Bill Gates, Centrica Innovations, Kck, Khosla Ventures, Louis M. Bacon, Statoil Energy Ventures
	08/29/2017	Series B	$40.04MM	$xx.xx	$110.16MM	Undisclosed Investors
Price per Share $xx.xx Shares Outstanding 10,569,940 Liquidation Pref Order 5 Liquidation Pref As Multiplier 1.0x Conversion Ratio 1.0x Dividend Rate 8.0% Cumulative Non-cumulative Participating Non-participating Participation Cap -- Key Investors Undisclosed Investors
	07/01/2011	Series A-1	$7MM	$xx.xx	$25.97MM	Undisclosed Investors
Price per Share $xx.xx Shares Outstanding 3,708,413 Liquidation Pref Order 5 Liquidation Pref As Multiplier 1.0x Conversion Ratio 1.0x Dividend Rate 8.0% Cumulative Non-cumulative Participating Non-participating Participation Cap -- Key Investors Undisclosed Investors
	07/01/2011	Series A	$2.86MM	$xx.xx	$25.97MM	Undisclosed Investors
Price per Share $xx.xx Shares Outstanding 3,169,952 Liquidation Pref Order 5 Liquidation Pref As Multiplier 1.0x Conversion Ratio 1.0x Dividend Rate 8.0% Cumulative Non-cumulative Participating Non-participating Participation Cap -- Key Investors Undisclosed Investors

Access Stock Price

Private companies exploring an IPO

					Last Funding Round
Company		Forge Price	Forge Price Change ⁵	Last Closed Trade	Share Class	Post-Money Valuation	Price per Share	Amount Raised
	OpenAI	$469.47	-0.01%	$xx.xx	Funding Round	--	--	--
	Anduril	$40.88	-3.86%	$xx.xx	Series G	$30.5B	$xx.xx	$2.5B
	Cerebras	$31.35	-0.16%	$xx.xx	Series F-1	$2.87B	$xx.xx	$420MM
	Figma	$38.00	+0.03%	$xx.xx	Series E	$10B	$xx.xx	$200MM
	Kraken	$31.63	+11.77%	$xx.xx	Series B	$5.52B	$xx.xx	$52.5MM
	Netskope	$14.50	+8.45%	$xx.xx	Series H	$7.5B	$xx.xx	$300MM
	Shein	--	--	$xx.xx	--	--	--	--
	Klarna	$37.31	+21.02%	$xx.xx	Unknown	--	--	--
	Discord	$239.72	+6.61%	$xx.xx	Series I	$15B	$xx.xx	$500MM
	HeartFlow	--	--	$xx.xx	Series E	$1.65B	$xx.xx	$305MM

See Tech IPO Calendar

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Updated on: Jul 9, 2025

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Mainspring IPO