We Replaced the Letter of Credit with 400 Lines of Public Code
Small solar installers pay 20–40% more for panels and inverters than utilities do, because they buy alone. Techs.Solar's Group Purchasing Orders let them buy together — and the hardest problem wasn't logistics. It was trust: who holds a group's money while a container crosses the sea?
Our answer: nobody.
The Problem Nobody Talks About
Aggregated procurement is an old idea with a stubborn bottleneck. Ten small companies pooling €100,000 for a container of solar equipment need an answer to one question before anything else: who holds the money?
The traditional answers are painful for SME-sized deals:
- A bank Letter of Credit costs 1–3% plus fees and weeks of paperwork. Banks barely want sub-€500K LC business.
- An external escrow agent adds their own fees, their own counterparty risk, and their own paperwork.
- "Just trust the coordinator" is how group-buying horror stories start.
The trust cost — not the logistics — is what keeps small installers paying retail. We decided to attack exactly that line item.
What We Built
For every group order, we create a single-purpose escrow program on a public ledger (Gnosis Chain — an EU-friendly, low-cost network). Its rules are fixed at creation and are physically unchangeable afterwards — by us, by the supplier, by anyone. The rules are short enough to summarise completely:
Money in.
Only pre-registered group members, only their exact committed amounts, only in EURe — euro e-money issued by Monerium, an authorised EU e-money institution, regulated under MiCA — the EU's 2024 Markets-in-Crypto-Assets regulation that frames e-money and stablecoins — and redeemable 1:1 for bank euros by law. Members just send a SEPA transfer. No exchange rates, no volatility, no "crypto" anywhere in the user experience.
Money out, to the supplier.
Three slices — 30% when the order enters the production queue, 40% when the goods are on the ship, 30% on arrival and customs clearance. Each slice requires cryptographic sign-off from two independent parties (for example, the manufacturer and the shipping line). Nobody — including us — can release the major payments alone.
Money out, back to the members.
Every stage has a deadline. When a deadline passes unmet, members' refund rights switch on automatically, by clock — no committee, no customer-service ticket, no dependence on Techs.Solar even existing. Members holding >51% of an order's value can also vote to unwind it early.
There is no third path.
No admin withdrawal, no fee siphon, no upgrade switch. 100% of the goods payment ends with the supplier or back with the members, and anyone can verify this on the public ledger in real time.
Emergency brake exists.
Held jointly by three independent parties, usable only by two of them together. It can only pause supplier payments while something is investigated — it cannot touch funds, and it can never block member refunds. It expires by itself after 30 days, so nobody can freeze a group's money indefinitely.
"Is This a Crypto Thing?"
It's a ledger thing. The euros stay euros: MiCA-regulated e-money, fully reserved, issued by a licensed EU institution, redeemable at par by law — never sitting on our balance sheet, never exposed to a coin price.
What the public ledger contributes is something a bank statement can't: rules that execute themselves and books that anyone can audit, live, without permission. The escrow code is currently with an independent security audit firm, and we've published a full dress rehearsal on a public test network — complete order lifecycles, deliberately failed orders with automatic refunds, emergency-pause drills, and attack attempts, all rejected and all publicly recorded. No real order runs before the audit closes.
What It Changes Commercially
| Bank LC | Escrow agent | GPO smart escrow | |
|---|---|---|---|
| Cost on a €100K order | €1,000–3,000 + fees | €1,500+ | under €5 of network costs |
| Setup time | weeks | days–weeks | minutes |
| Verifiable by members | no | no | yes, live, by anyone |
| Survives the coordinator failing | n/a | poorly | by design |
That deleted cost line — plus the paperwork weeks — is precisely what made group purchasing impractical at SME scale. Remove it, and ten three-person installer companies can buy a container with the financial discipline of a multinational's procurement department.
The Legal Layer (Because Code Is Not a Contract)
The escrow is the operational layer of a real, lawyer-drafted Member Agreement under Greek law, signed with qualified e-signatures recognised EU-wide (eIDAS), with EU-wide enforceability of its jurisdiction and governing-law choices (Brussels Ia / Rome I). The point isn't "code replaces law" — it's that the code makes the fast 99% of outcomes self-executing, while the contract stands behind the slow 1%. And because MiCA harmonised e-money across the EU, the same architecture opens any EU market without per-country banking or escrow setup — which is exactly our expansion plan.
See It Live
The smart contract is currently deployed on Gnosis Chiado (Ethereum's EU-friendly testnet) and has completed a full dress rehearsal: complete order lifecycles, deliberately failed orders with automatic refunds, emergency-pause drills, and adversarial attack attempts — all rejected, all on the public record. You can browse five demo scenarios — from a freshly funding GPO to one that completed end-to-end — directly from your installer dashboard.
Installer login required · no real funds · no real chain calls
Verify Our Security
This isn't a marketing claim. Every result below comes from a recorded run and says which contract version it covers. The contract repository is currently private; the live CI link is added here when it is published.
Continuous integration — view live runs
CI badge link activated after public contract repo is pushed (follow-up PR).
| What's been verified | Result | Where to verify |
|---|---|---|
| Unit + integration tests | 73 passing on the current contracts (194 across the repository, incl. the retired design) · 94.9% line coverage of the current contracts (13 Sept 2026) | CI run on the current contracts (link added when the repository is published) |
| Static analysis (Slither) | Runs on every change. Last full triage: 0 high, 0 medium true positives — on the previous contract version; triage of the current contracts pending | Triage record in repo /docs/slither-triage.md |
| Property-based fuzzing (24h Echidna) | Previous contract version: 500M+ call sequences, 6/6 invariants held. Not yet re-run on the current contracts | Campaign log in repo /echidna-24h.log |
| Live Chiado rehearsal | Previous version: S1–S5 run on Chiado; S3 and S5 failed our commercial criteria and drove the redesign. Current version: rehearsal in progress (Sept 2026) | Deployment record in repo /docs/chiado-deployment-record.md |
| Professional security audit | Pending — not yet commissioned, and required before real orders run at scale. Meanwhile, a separate independent review (an AI audit session with no prior involvement, 13 Sept 2026) found 14 issues; the high-severity ones are fixed in the current contracts. | Audit report linked here when completed; the independent review's findings and fixes are on record in the contract repository |
What this does NOT prove (honest disclosure): the CI verifies all 194 tests pass against the source. It does not prove the tests themselves are complete, or that no logic bugs exist outside test coverage — that is what a professional audit is for, and it is still pending. Of the checks above, only the automated test suite must pass on every change (static analysis runs alongside it as an advisory check); fuzzing and the live rehearsal are run separately, and the table says which contract version each one covers. They are a defence layer, not a replacement for the audit.
Become a Founding Installer
We're selecting the founding members of the first pilot Group Purchasing Order now — 5–10 installers, ~€50K target volume, panels from a Tier-1 manufacturer with Monerium-native settlement. If you're a solar installer in the EU and want utility-grade pricing with provable fund safety — without a bank in the middle — we want to talk.
PUBLIC LAUNCH
16 September 2026
Technical note for the curious: one immutable contract per member, multi-signature milestone approvals, refund rights that open when an order ends, and a pause guardian that can never move funds — the test-network contract addresses are public, the code will be published before mainnet, and the professional audit (pending) will be published when it is done. We're happy to nerd out — reach us via the contact form.