TL;DR: If you are replacing Kapacity.io, the closest options are Boost Biomes, ThereCraft, Apollo Atomics, Inc.. The table below compares 12 alternatives on what they do, stage, size and status.
Every alternative below is compared on what it actually does, not just its category — so you can see which one genuinely replaces Kapacity.io (YC Summer 2021).
Last verified:
The three closest alternatives to Kapacity.io are:
| Alternative | What it does | Stage | Team | Status |
|---|---|---|---|---|
| Boost Biomes | — | YC Summer 2019 | 12 | Inactive |
| ThereCraft | — | YC Summer 2017 | 1 | Active |
| Apollo Atomics, Inc. | We make the most compact nuclear reactors | YC Spring 2026 | — | Active |
| Helion Energy | Building the world's first fusion power plant | YC Summer 2014 | 150 | Active |
| Airthium | Decarbonized heat and power cheaper than fossil fuels | YC Summer 2017 | 18 | Active |
| Rewbi | A stealth mode startup. | YC Summer 2024 | 3 | Active |
| Inviscid AI | Real-time Physics Simulations for Industrial Facilities & Data Centers | YC Winter 2026 | 2 | Active |
| Bright | Sunrun for the developing world | YC Winter 2015 | 100 | Active |
| Paces | Agentic AI for Power Projects and AI Infrastructure | YC Summer 2022 | 48 | Active |
| Rise Reforming | We turn waste gases into valuable supply-secure chemicals | YC Summer 2026 | 4 | Active |
| Evoly | Smart electric & water meters as a service | YC Summer 2022 | 4 | Active |
| Green Energy Exchange | We deliver affordable renewable energy direct to customers and are… | YC Winter 2019 | 3 | Inactive |
It depends on your size. Boost Biomes is the closest match on what Kapacity.io actually does. If you need something more established, sort the table by team size — larger teams generally mean more support and a longer track record. If budget is the constraint, the earlier-batch companies are usually the ones still competing on price.
Kapacity.io has been acquired, which often means pricing, roadmap or support changes. That is the usual reason people start looking at this list.
Every company here is Y Combinator-backed and was matched to Kapacity.io on what it actually does — its own description of its product — rather than on a broad category label. Batch, team size and operating status come from the YC directory and are shown as-is. We do not rank by payment.
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