OneSun

What OneSun does

OneSun (One Sun, Inc.) is a privately-held commercial solar engineering, procurement, and construction (EPC) contractor headquartered in Graton, California, founded in 2009 by Warren Brown. The company designs and installs grid-tied solar photovoltaic systems for commercial, industrial, agricultural, municipal, and educational customers across Northern California, with documented projects in Sonoma County, San Francisco, Sacramento, San Jose, and the North and South Bay regions. Reported cumulative installed capacity exceeds 12 million kW (as stated in source data; figure appears inconsistent with company size and is likely a units error for ~12 MW), spread across more than 700 commercial installations.

The firm's technical offering combines turn-key PV system delivery with web-based monitoring, SCADA integration, and ongoing operations and maintenance services. OneSun has expanded beyond pure PV into adjacent product lines including solar-powered EV charging stations deployed on public schools and thermal cogeneration systems, the latter made possible through a partnership with Cogenra Solar that produced what the firm describes as the first dairy co-generation solar project in the United States. Core inverter partnerships include Enphase Energy for microinverter-based commercial systems.

OneSun operates a project-based revenue model with contract values visible in the $1M-$12M range per major deployment (e.g., 2.4 MW Sonoma County schools, 1.6 MW Constellation Brands), supplemented by recurring O&M and monitoring revenue. The firm is privately funded, with disclosed capital raises of $5.85M in November 2010 and $35.3M in December 2011 — totals that are unusually large for a sub-100 employee regional EPC and likely include project financing or tax equity rather than operating capital alone. The go-to-market emphasizes public-sector bidding (school districts, municipal buildings), known brand-name commercial customers (Williams Selyem, Clover Stornetta, Wells Fargo Center for the Arts, First Northern Bank), and agricultural/winery verticals where the firm has built a visible book of business.

Name

OneSun

Legal name

One Sun, Inc.

Website

https://onesuninc.com

Company type

Private

Founded year

2009

Operating status

Operating

Headcount range

51–100 employees

Short description

OneSun is a Northern California commercial solar EPC contractor founded in 2009, serving wineries, agriculture, schools, municipal, and industrial clients with grid-tied PV, EV charging, and cogeneration systems across Sonoma County, San Francisco, Sacramento, and the Bay Area.

Ownership category

akta.pro rank

Product category

Commercial Solar Installation Services (EPC)

NAICS

Solar Electric Power Generation (221114)

SIC

Cogeneration Services & Small Power Producers (4991)

akta.pro primary industry

Solar EPC & Construction (Utility-Scale, Rooftop, Balance of System) (EUAMABAB)

akta.pro secondary industries

Commissioning, Testing & Energization Services (Pre-Commissioning, Grid Code Compliance) (EUAMAFAK), Solar Balance-of-Plant EPC (Piles/Foundations, Trenching, Combiner Networks) (EUAEADAJ), Electrical Balance-of-Plant EPC (MV Collection, Cabling, Earthing, Lighting) (EUAEADAB), Civil & Site Works EPC (Earthworks, Roads, Drainage, Foundations) (EUAEADAA)

Keywords

• Commercial solar installation
• Solar EPC services
• Photovoltaic systems
• Solar financing
• Solar maintenance services

Headquarters

HQ city

Graton

HQ country

United States

HQ region

North America

Offices1 record

Markets served

GTM type

B2B

Offering type

Services

Cost components

Personnel, Operations, Supply Chain, Marketing or Sales, Technology or R&D, Infrastructure

Revenue model

1. Solar System Design and Installation: Full EPC (Engineering, Procurement, Construction) turn-key services for solar PV systems. The company designs custom systems, procures materials, and constructs installations for commercial, industrial, municipal, and agricultural clients. Revenue is generated through upfront project fees for system design and installation.
2. Solar Lease Agreements: Through strategic financial partners, One Sun facilitates lease agreements where clients make monthly payments for a fixed period (usually 10 years). At the end of the period, clients can purchase the system. This option requires no up-front costs.
3. Power Purchase Agreement (PPA): Third-party financing where clients buy electricity from the power provider at a fixed rate below market price. Requires no up-front capital. May include a buy-back opportunity.
4. Maintenance Services: Preventive and corrective maintenance for grid-tied commercial and industrial photovoltaic systems. Services include visual/electrical inspections, module cleaning, infrared scans, inverter maintenance, thermal imaging, battery health audits, and remote diagnostics.

Pricing tiers

Go-to-market motion1 record

Distribution channels1 record

Marketing channels7 records

Core offering

OneSun designs, procures, and installs turn-key grid-tied commercial solar photovoltaic, cogeneration, and thermal systems for businesses, agricultural operations, wineries, schools, and municipal facilities in Northern California. The company offers full EPC delivery from site assessment and feasibility through grid interconnection and post-installation monitoring, complemented by preventive maintenance, performance monitoring, and financing facilitation (leases and PPAs).

Product overview

OneSun is a commercial solar installation company offering EPC (Engineering, Procurement, Construction) turnkey services for grid-tied solar systems in Northern California. The core product is the Grid-Tied Solar Photovoltaic System, which is complemented by specialized modules including Solar Cogeneration Systems for facilities requiring hot water (such as dairies and food processors), Solar Thermal Systems for commercial thermal energy needs, and Solar-Powered EV Charging Stations. Installation options span Rooftop Mount Systems, Ground-Mount Systems, and Carport/Parking Structure Systems. Supporting services include Web-Based Performance Monitoring for real-time system oversight, Preventive and Corrective Maintenance Services with options like Automatic Sprinkler Cleaning Systems, and flexible Financing Options (Lease, PPA, and Cash Purchase). The company serves diverse markets including wineries, agriculture, food processing, manufacturing, warehousing, public works, and schools.

Differentiator

Problem solved

Functional benefit

Products and services

• Grid-Tied Solar Photovoltaic (PV) Systems Commercial and industrial grid-tied solar electric systems with photovoltaic panels, inverters, and net metering capabilities for businesses, wineries, agricultural, and municipal clients in Northern California.
• Solar Cogeneration Systems Hybrid solar systems combining photovoltaic electricity generation with thermal energy capture for facilities requiring large amounts of hot water, such as dairies and food processing operations.
• Solar Thermal Systems Commercial flat-plate thermal systems capturing solar energy for hot water production in industrial, municipal, and winery applications requiring significant thermal energy.
• Solar-Powered Electric Vehicle Charging Stations Solar-powered EV charging stations using solar panels to collect energy with modules for electric vehicles; compatible with all EV brands including Chevy Volt, Nissan Leaf, and Tesla; available with optional automated payment processing.
• Preventive and Corrective Maintenance Services Scheduled visual and electrical inspections, infrared scans, module cleaning, inverter maintenance, thermal imaging, battery health audits, and 24/7 remote diagnostics for commercial photovoltaic systems in Northern California.
• Solar Financing Options (Cash, Lease, PPA) Facilitated financial solutions including cash purchase with tax credit eligibility, operating leases with fixed monthly payments (typically 10 years) and end-of-term purchase option, and Power Purchase Agreements (PPAs) with no up-front capital and electricity purchased at fixed rates below market price.

Quantifiable outcome

• 20% to 40% reduction in electricity expenses in first year of operation
• +4 more outcomes

Named customers21 records

Segments5 records

Ideal customer profiles4 records

Technology focussed No

API detail

Has API

No

API docs

API detail

Core technology

AI maturity

App detail

Feature5 records

Partnerships

Five partnerships are on record, tiered core and minor.

• Enphase EnergycoreTechnology or Integration · 19 November 2012Enphase microinverter technology used in major projects including the Wells Fargo Center for the Arts 400kW installation. Enphase provides power electronics for the solar installations enabling optimized energy production and monitoring.
• Cogenra SolarcoreTechnology or IntegrationStrategic partnership for solar cogeneration systems. One Sun installed the first solar cogeneration system on a dairy in the U.S. with Cogenra technology. Cogenra provides hybrid systems that create more power via heat and electricity combination, especially suited for facilities requiring large amounts of hot water like food processing and winery operations.
• PG&EcoreTechnology or IntegrationPacific Gas and Electric Company - utility provider for grid interconnection and net metering. One Sun interfaces with PG&E for tie-in and interconnection services. Coordinates for PG&E Rule 21 interconnections and ongoing utility relationships.
• SMUD (Sacramento Municipal Utility District)coreTechnology or IntegrationSacramento Municipal Utility District - utility provider for grid interconnection and net metering in Sacramento service territory. Coordinates for SMUD interconnections alongside PG&E for Northern California coverage.
• Solar RichmondminorOthersCity-sponsored program from which One Sun employs trainees transitioning to the renewable energy sector. Community workforce development partnership supporting local hiring and training.

Scale indicators8 records

Recent moves6 records

Expansion highlights5 records

Direct peers

• Borrego Solar: Commercial and industrial solar EPC contractor operating across multiple U.S. states with turnkey design-build services. Highly comparable to OneSun's C&I EPC turnkey model, though at significantly larger scale and broader geography.
• REC Solar (Duke Energy Renewables): Commercial solar EPC and developer serving C&I customers with turnkey installations. Direct comparable in service offering, now backed by Duke Energy balance sheet, which contrasts with OneSun's independent regional positioning.
• SP Solar (Solar Provider Group): Commercial solar EPC and finance provider serving C&I clients across multiple U.S. markets. Comparable in offering turnkey EPC, PPAs, and leases to mid-market commercial customers like OneSun's winery and school segments.
• Namaste Solar: Employee-owned commercial and residential solar installer with strong regional brand (Colorado) and emphasis on quality installation. Comparable mission-driven, mid-sized C&I EPC peer to OneSun.
• Baker Electric Solar: Southern California-based commercial and residential solar EPC. Closest geographic peer to OneSun with similar C&I focus, contractor-license foundation, and turnkey project delivery model.
• Solar Optimum: California-based commercial and residential solar installer with strong SoCal presence. Comparable as a regional California C&I EPC competing in the same broader market as OneSun.

Others

• GRID Alternatives: Nonprofit solar installer focused on low-income and workforce development projects. Comparable solar installer operating model and OneSun's Solar Richmond workforce partnership make it an ecosystem/values-aligned peer rather than direct competitor.

Regional players

• Sullivan Solar Power: San Diego-based solar installer with both residential and commercial focus. Geographic peer operating in California's southern markets; partial overlap in C&I commercial solar work.

Broad incumbents

• Tesla Energy (SolarCity legacy): National solar and storage provider with commercial offerings and Tesla balance sheet. Indirect competitor at the larger end of the C&I market where scale, financing, and battery integration matter.
• SunPower (Commercial / Total Energy Solutions): National commercial solar developer with strong California presence and full suite of panels, inverters, and turnkey C&I services. Represents the broad incumbent against which regional EPCs like OneSun compete for large accounts.

Market position

Strengths4 records

Weaknesses4 records

Competitive moat4 records

Key risks6 records

Key highlights6 records

Customer concentration

• Facebookfacebook.com/pages/One-Sun-Inc/200184426704339?sk=wall
• LinkedInlinkedin.com/company/one-sun-inc-

Compliance7 records

Revenue estimate

Valuation estimate

Number of profiles

Profiles1 record

Funding overview

Funding rounds2 records

Investors

Funding detail is available on the Subscription and Enterprise plan.Contact sales →

M&A

Investments

M&A and investment is available on the Subscription and Enterprise plan.Contact sales →

Frequently asked questions about OneSun