| EMERALD VALLEY WASTEWATER COMPANY LLCPortland, OR · Active | Portland, OR | LLC | Jun 23, 2016 | Active |
| NORTHWEST NATURAL HOLDING COMPANYPortland, OR · Active | Portland, OR | Corporation | Mar 7, 2018 | Active |
| NORTHWEST NATURAL GAS COMPANYPortland, OR · Active | Portland, OR | Corporation | Jan 10, 1910 | Active |
| BENTS COURT WATER COMPANY, LLCPortland, OR · Active | Portland, OR | LLC | Jul 16, 2018 | Active |
| NW NATURAL WATER OF OREGON, LLCPortland, OR · Active | Portland, OR | LLC | Oct 10, 2018 | Active |
| LAKESHORE WATER COMPANY, LLCPortland, OR · Active | Portland, OR | LLC | Oct 12, 2018 | Active |
| SEAVEY LOOP WATER COMPANY, LLCPortland, OR · Active | Portland, OR | LLC | Oct 12, 2018 | Active |
| SOUTH COAST WATER COMPANY, LLCPortland, OR · Active | Portland, OR | LLC | Oct 12, 2018 | Active |
| SUNSTONE WATER, LLCPortland, OR · Active | Portland, OR | LLC | Mar 15, 2019 | Active |
| SUNSTONE INFRASTRUCTURE, LLCPortland, OR · Active | Portland, OR | LLC | Jun 10, 2019 | Active |
| NW NATURAL RNG HOLDING COMPANY, LLCPortland, OR · Active | Portland, OR | LLC | Nov 4, 2020 | Active |
| NW NATURAL RENEWABLES HOLDINGS, LLCPortland, OR · Active | Portland, OR | LLC | Aug 31, 2021 | Active |
| NW NATURAL OHIO RENEWABLE ENERGY, LLCPortland, OR · Active | Portland, OR | LLC | Aug 31, 2021 | Active |
| NNG FINANCIAL CORPORATIONPortland, OR · Active | Portland, OR | Corporation | Aug 23, 1984 | Active |
| NW NATURAL WATER SERVICES, LLCPortland, OR · Active | Portland, OR | LLC | Feb 6, 2023 | Active |
| PUMICE INFRASTRUCTURE, LLCPortland, OR · Active | Portland, OR | LLC | Jun 4, 2024 | Active |
| KB PIPELINE COMPANYPortland, OR · Active | Portland, OR | Corporation | Feb 21, 1991 | Active |
| TOLEDO RENEWABLE ENERGY, LLCPortland, OR · Active | Portland, OR | LLC | Jun 18, 2025 | Active |
| SUNRIVER WATER LLCSunriver, OR · Active | Sunriver, OR | LLC | Jan 29, 1998 | Active |
| SUNRIVER ENVIRONMENTAL LLCSunriver, OR · Active | Sunriver, OR | LLC | Jan 29, 1998 | Active |
| NW NATURAL GAS STORAGE, LLCPortland, OR · Active | Portland, OR | LLC | Jul 31, 2009 | Active |
| SALMON VALLEY WATER COMPANYPortland, OR · Active | Portland, OR | Corporation | Jan 3, 1968 | Active |