Sum Ventures
SUM Ventures is an early-stage venture capital firm in Santa Monica, California that backs pre-seed and seed founders across fintech, proptech, AI and climate. Founded in 2016 as Startup Mavericks, its water exposure is occasional: Leviathan tracks a single water company, robotic-irrigation maker Irrigreen, across two rounds as of 2025.
Compiled by Antoine Walter, (don't) Waste Water, from official filings and direct intelligence in Leviathan.
The take
SUM Ventures is one of those generalist seed funds that found water almost by accident. It began life in 2016 as Startup Mavericks, the vehicle of Garrett Gilbertson, an Air Force Academy graduate and Afghan War veteran who chairs the Band of Angels group in Los Angeles, and it writes first cheques into fintech, proptech, AI and climate from offices in Santa Monica, San Francisco and Chicago.
SUM Ventures keeps water to a small corner of that portfolio. In the Leviathan database it shows up on one water company across two rounds: Irrigreen, the robotic-sprinkler startup whose single nozzle maps a lawn and lays down water only where it is needed. It is a proptech-flavoured water bet, the kind of deal a property-and-climate generalist reaches when water-saving hardware also happens to sell to homeowners.
SUM Ventures keeps good company on that one deal. The Irrigreen rounds put it alongside the funds that water actually specialise in, names like Burnt Island Ventures, Ulu Ventures and Echo River Capital, so even an occasional water cheque lands SUM in the room with the category's regulars.
SUM Ventures is, for a newcomer, a simple read. It is a broad early-stage fund that happens to hold a single, water-saving company, rather than a water investor. If you are mapping who backs water, SUM is a name that turns up at the edges, most often where smart hardware meets the home.
Water Commitment Score
Compiled from official filings, third-party records, and direct intelligence from investors and founders, in Leviathan · recomputed monthly · as of Jun 2026.
How they invest
Portfolio · 1 water companies
Invests alongside
Highlighted = profiled on (don't) Waste Water.
Frequently asked
- What does SUM Ventures invest in?
- SUM Ventures invests in pre-seed and seed-stage technology startups, with a stated focus on fintech and proptech and opportunistic bets across AI, climate and health. Based in Santa Monica, California, it backs founders at the earliest stages and supports them with mentorship and an advisor network through later growth rounds.
- Does SUM Ventures invest in water?
- SUM Ventures is not a dedicated water fund, but it makes occasional water-related bets. In the Leviathan database it is tied to one water company, the robotic-irrigation startup Irrigreen, which it backed across two rounds through 2025. (don't) Waste Water rates its overall water commitment Occasional.
- Who runs SUM Ventures?
- SUM Ventures was founded and is led by Garrett Gilbertson, its Managing Partner, a former US Air Force captain and Afghan War veteran who also chairs the Band of Angels group in Los Angeles. The senior team includes Raj Khoshoo, a former Siemens executive, and partner Derek Hu.
- Where is SUM Ventures based?
- SUM Ventures is headquartered in Santa Monica, California, with additional offices in San Francisco and Chicago. The firm was founded in 2016, originally under the name Startup Mavericks, and invests primarily in United States based early-stage technology companies.
- Is SUM Ventures the same as Greater Sum Ventures?
- No. SUM Ventures is an early-stage technology venture firm in Santa Monica, California, led by Garrett Gilbertson. Greater Sum Ventures is a separate, unrelated private investment firm. The names look alike but the teams, locations and strategies differ, so check the website at sum.vc to be sure.