Rondo Energy, Inc.

Overview

Rondo Energy builds electrically charged heat batteries for industrial plants. Resistive heaters warm stacks of refractory brick during cheap or surplus power hours, and air blown through the stack carries the heat out as superheated air or steam. The company was founded in 2020 by John O'Donnell and Pete von Behrens, both from concentrating solar thermal; Rondo's biography says O'Donnell co-founded GlassPoint Solar and, before that, Ausra. It is incorporated in Delaware as Rondo Energy, Inc. and uses an Alameda, California dateline on its releases.

Eric Trusiewicz has been chief executive since June 19, 2024, when O'Donnell wrote that Trusiewicz "has stepped up to lead Rondo Energy as CEO" and that he was moving to chief innovation officer. Rondo's biography says Trusiewicz joined as a strategic advisor in early 2021, after work as an entrepreneur in residence at Breakthrough Energy Ventures and more than a decade at a multinational cement company. Von Behrens is chief technology officer, Karim Ibrik chief operating officer and Tony Meneghetti chief financial officer. Rondo publishes no headcount and no board list.

The documented operating record is three units: a 2 MWh pilot at Calgren Renewable Fuels in California since 2023, a 100 MWh unit at a Holmes Western Oil Corp. site in Kern County whose commercial operation Rondo announced on October 16, 2025, and a 33 MWh unit at a Siam Cement Group (SCG) plant in Thailand that started in November 2025. One 100 MWh unit is under construction in Germany and two more are in development in Portugal and Denmark. Rondo's homepage says it has announced "11 commercial developments, including 8 RHB deployments"; no source located for this profile names eight units, and the company does not list them.

How the heat battery works

Rondo's product is the Rondo Heat Battery (RHB). Its how-it-works page describes "thousands of tons of brick" heated to as much as 1,500°C; the homepage gives a range of 1,100 to 1,500°C. Air flows up through the brick and leaves above 1,000°C, and the delivery rate is set by the air flow. Output options listed by Rondo are superheated air, superheated or saturated steam, and heated thermal oil. The battery itself discharges only heat. Where Rondo markets electric power, the steam drives a conventional steam turbine, as at the SCG unit, and its products page quotes "c. 4:1 ratio of heat:electricity delivery, case dependent" for that configuration.

Charging is meant to fit a short daily window. The homepage says 6 to 8 hours a day, the 2022 product launch said as little as 4 hours, and pv magazine USA quoted Rondo in October 2025 saying the Holmes Western unit charges "using only the six lowest-cost hours of electricity per day." The 2022 launch named two models, RHB100 and RHB300, without publishing specifications for either; the Thailand unit is an RHB33. Rondo's current product page says a single unit can be sized from 2 MWth to over 100 MWth. Latitude Media reported in December 2024 that Rondo enlarged its cast bricks from about 50 kg to cut labor, and that producing the larger bricks took about six months longer than expected.

Rondo quotes its efficiency several ways. The March 2023 Calgren release claimed "documented efficiency over 90%" for the pilot and said larger units store energy at over 98% efficiency. The October 2025 Holmes Western release claimed "round-trip efficiency above 97%." The products page says "97%+" and the homepage says 98%. Every one of these figures runs from electricity in to heat out; none is electricity to electricity. Rondo has not said whether the figures count fan and blower loads, steam generator losses or standby loss across a cycle, or over what period they were averaged, and no independent test report from a national laboratory or certification body could be located.

The other performance claims carry the same caveat. Rondo's how-it-works page gives standby loss of "less than 1% per day" and a "50-year life"; its homepage says "40+ year life." Neither life figure can be demonstrated yet, since the oldest unit began operating in 2023.

Deployments

Funding & investors

Rondo has announced two equity rounds with amounts. The $22 million Series A, announced on February 8, 2022, was led by Breakthrough Energy Ventures and Energy Impact Partners. On August 16, 2023 Rondo said it had "raised $60 million in a new financing"; the release gives no series letter. Existing investors Breakthrough Energy Ventures, Energy Impact Partners, SCG and TITAN Cement Group took part, joined by Microsoft's Climate Innovation Fund, Rio Tinto, SABIC, Aramco Ventures, SDCL Energy Efficiency Income Trust (SEEIT) and John Doerr. Six of the strategic investors joined a Strategic Investor Advisory Board. The two announced rounds add to $82 million, the figure Heatmap also reported as raised to date.

Several strategic checks came without amounts. TITAN joined the Series A in 2022 and said in July 2023 that it had expanded its investment. SCG invested in September 2022 under a letter of intent to develop and expand use of the technology. H&M Group Ventures invested in June 2024, which FashionUnited reported was its first investment in decarbonization technology. Axios reported in June 2024 that Trusiewicz said Rondo was preparing to raise more than $100 million. No valuation has been disclosed by Rondo or any investor.

The only SEC filing is a Form D filed on June 17, 2022, reporting $25,116,635 of equity sold to 7 investors, with first sale on January 4, 2022. No source explains the gap with the announced $22 million. No Form D exists for the 2023 round; the absence of a filing does not by itself show how much was raised. Rondo's homepage says it has announced "more than $160 million in funding" without a breakdown. The two equity rounds plus the €75 million European package below come to roughly that, but that reconciliation is Blizzard Power's inference, and the package is conditional project finance rather than corporate equity.

The European package was announced on June 26, 2024 as €75 million of "grants and venture debt, subject to funding conditions," from Breakthrough Energy Catalyst and the European Investment Bank under the EU-Catalyst Partnership, backed by InvestEU. The EIB's project page (reference 20230665) shows €35 million of EIB financing to Rondo Energy Inc. against a total project cost of €78 million, covering three 100 MWh RHB100 units in Germany, Denmark and Portugal; it was approved on June 24, 2024 and signed on December 11, 2024. Neither Rondo nor the EIB states the Catalyst grant amount. Subtracting the EIB loan from the €75 million total gives €40 million, which is arithmetic. How much of either has been drawn is not public.

SCG is also Rondo's manufacturing partner. In June 2023 the companies said an SCG facility in Thailand had 2.4 GWh a year of heat battery production capacity and would be expanded to 90 GWh a year; a spokesperson told Electrek the expansion would come over the next few years, with no date. MIT Technology Review repeated the 2.4 GWh figure in October 2025. Sources differ on whether the Thai plant makes brick material or complete units, and no source shows capacity above 2.4 GWh a year built or reports actual output. No Rondo manufacturing site in the United States could be located.

Market & competition

A heat battery competes with a gas boiler on the price of the energy that charges it. US industrial customers paid an average of 9.77 cents per kWh for electricity in July 2026, per EIA's Electric Power Monthly Table 5.3 released September 24, 2026, and $4.58 per thousand cubic feet for natural gas, per EIA series N3035US3 released September 30, 2026; EIA flags the 2025 and 2026 electricity figures as preliminary. At 3,412 Btu per kWh and about 1,037 Btu per cubic foot, that is roughly $28.60 per MMBtu for electricity against $4.42 for gas, a ratio of about 6.5 to 1. On 2025 annual averages (8.62 cents and $5.23) the ratio is about 5 to 1.

Allowing for an 85% efficient gas boiler and taking Rondo's claimed 98% at face value, the battery matches July 2026 gas heat on energy cost alone when charging power costs about $17 per MWh, or about $20 per MWh at 2025 gas prices, before any capital cost. These conversions are Blizzard Power arithmetic on the EIA series. On these numbers, a heat battery charged at average industrial tariffs does not compete with gas on fuel cost, which is consistent with Rondo's first full-scale unit running on its own off-grid solar and with its pitch to charge in the cheapest hours of the day.

Rondo has published no delivered heat price. The one number on record is a target: Canary Media reported in October 2025 that O'Donnell said Rondo is targeting $30 per megawatt-hour for the energy storage services its heat batteries provide, and that the Holmes Western project is "not close" to that price. Whether the target includes the electricity is not stated. In an October 2022 presentation to the California Air Resources Board, Rondo put electric thermal storage at 1.5 times the cost of natural gas before Inflation Reduction Act credits and 0.8 times after, without giving absolute prices or naming the credits.

Outside studies come with sponsors. Brattle's October 2023 study for C2ES and the Renewable Thermal Collaborative, a coalition of industrial heat buyers, found that "thermal batteries can be cost-competitive with natural gas in much of the US even today, though the strength of the business case depends on the configuration of electricity supply, location, access to wholesale power prices, any greenhouse gas (GHG) price that may be applied, and eligibility for policy support." Brattle's June 2024 presentation of the study used a gas benchmark of $6 per MMBtu, above the July 2026 industrial price. Jeff Rissman of the policy think tank Energy Innovation put thermal battery heat at $35 to $62 per MWh-thermal in the locations Energy Innovation studied, in a September 2023 interview with Thermal Processing; the electricity price behind that range was not located.

US tax treatment is unsettled. Section 48(c)(6) of the Internal Revenue Code defines thermal energy storage around building heating and cooling, so a unit that sells only process steam does not obviously qualify for the Section 48E storage credit; one that feeds a steam turbine may fit the branch for storage that delivers energy "for conversion to electricity." Section 45X sets a $45 per kWh credit for battery modules that do not use cells, and the final rules, as summarized by Mayer Brown, include thermal batteries in that category, but the credit applies to US production, and Rondo's stated capacity is in Thailand. Both readings are inference from the statute and law-firm summaries; no IRS guidance on industrial process-heat storage under Section 48E, and no claim of either credit by Rondo or a customer, could be located.

Under the EU Emissions Trading System, the 13,000 tonnes a year Covestro expects to save would be worth about €1.07 million a year at the €82.40 per tonne EU allowance price reported on October 5, 2026, a gross figure that ignores Covestro's free allocation, which is not public at site level.

Most competitors are private. Antora Energystores heat in carbon blocks and can discharge power through thermophotovoltaic cells; it closed a $550 million Series C in July 2026, began commissioning a 5 GWh system at POET's Big Stone City, South Dakota ethanol plant in May 2026, and on October 1, 2026 announced a 5.8 GWh "multi-day thermal energy storage project" at Pratt Energy's biorefinery in Kansas, with no power rating, timeline or cost given. Electrified Thermal Solutions, an MIT spinout using conductive firebrick, said in September 2026 that two Joule Hive units, 20 MWh initially, are to be deployed for Holcim, and that its first commercial-scale unit at Southwest Research Institute has logged more than 1,000 hours.

In Europe, Kraftblock's 20 MWh unit at Tata Steel's Jamshedpur works, which stores waste heat at about 500°C, was commissioned in May 2025, and Kyoto Group inaugurated a 56 MWh molten salt Heatcube at KALL Ingredients in Hungary in October 2025 under a 15-year heat-as-a-service contract. Brenmiller Energy, renamed BrenX Ltd. in July 2026, reported no revenue in the first half of 2026 and disclosed substantial doubt about its ability to continue as a going concern. By energy capacity, Holmes Western is nearly twice Kyoto's unit and one-fiftieth of Antora's Big Stone system.

Key considerations

Rondo has published no operating data for any of its three running units: no operating hours, cycle counts, availability, energy charged or delivered, steam tonnage, measured efficiency or measured standby loss. Calgren has run since 2023 and Holmes Western since about August 2025. Until those numbers appear, the 97% to 98% efficiency figures, the less-than-1% daily standby loss and the 40- or 50-year life rest on Rondo's own statements.

The full-scale reference unit sits on an oil field with its own solar array and no grid charging. The European units are Rondo's first 100 MWh systems in chemicals, brewing and an industrial park, and the Heineken unit charges partly from the grid, which puts tariffs back into the economics. Covestro's end-2026 start-up is the next public test. GreenLab has already missed its 2025 date.

The capital record stops in 2023. Rondo has announced no equity round since the $60 million in August 2023, and the raise of more than $100 million that Trusiewicz told Axios in June 2024 Rondo was preparing has not been announced. The €35 million EIB loan and the Catalyst grant are conditional and tied to three named projects. Rondo's headline counts (11 developments, 8 deployments, more than 400 MWh of announced projects and 3 GWh of partnerships on its homepage) carry no project list behind them, and the largest commercial prospect, Aramco, is an MOU.

Production capacity is 2.4 GWh a year at a partner's plant in Thailand, and the 90 GWh expansion has no date. Whether US buyers can claim Section 48E for heat-only units, and whether any Rondo hardware could earn Section 45X without US production, are unresolved on the public record.

Sources