The most reliable warning signs aren't price questions but process questions: a quote without a roof visit, pressure with expiring "promotional prices", high advance payments, missing technical details and warranty promises without a tangible warrantor. Each individual signal is a reason for follow-up questions – from two of them on, you should put the quote aside. (As of: July 2026)
Key points in brief
- Dubious providers are rarely recognised by their logo and almost always by their approach: speed, pressure and non-commitment on technical matters.
- The most expensive mistakes don't happen with the price, but with what is missing from the quote – scaffolding, electrical work, registrations, structural assessment.
- A reputable quote comes after a site visit, names components with type designations and stands up to the technical minimum-information checklist.
- Beware of payment plans: instalments by progress are customary in the industry – not 80 or 100 per cent in advance.
- Getting a second quote is not a declaration of distrust but standard – reputable providers welcome the comparison.
Why solar in particular? A market in gold-rush mode
Solar systems are in demand, the funding landscape is attractive, and the entry barriers for sales firms are low – you can sell systems without ever having set foot on a roof, and hand the installation to changing subcontractors. The great majority of providers work cleanly. But the environment also attracts structures whose business model isn't the system but the closing of the contract. The good news: these structures give themselves away – reliably and early, if you know what to look for.
The 9 red flags at a glance
| # | Warning signal | Why it matters |
|---|---|---|
| 1 | Quote without a site visit – only a satellite image and a phone call | Structure, tile condition, meter location, cable routes: unseen = unplanned. Supplements follow |
| 2 | Time pressure – "promotional price only valid this week" | A correctly calculated quote doesn't lose its validity in four weeks. Pressure replaces arguments |
| 3 | High advance payment – 80–100% before installation begins | Your money then secures the provider's liquidity, not your project |
| 4 | No type designations – "brand modules", "quality inverter" | Without a type, no price comparison, no warranty check, no inspection on delivery |
| 5 | Lump sum without a scope of services – scaffolding, AC work, registrations unclear | What isn't in it comes onto the bill later – or simply stays undone |
| 6 | Warranty promise without a warrantor – "25 years warranty on everything" | Product, performance and installation warranties are three different things with three debtors |
| 7 | No tangible company – no Swiss address, no references in the region, letterbox structure | Whoever is meant to bear the liability needs to still be findable in five years |
| 8 | Return promise with a pinpoint landing – "pays back in 7.2 years, guaranteed" | Serious calculations state assumptions and ranges; there are no guarantees for the future |
| 9 | Registrations are "your business" – grid operator, Pronovo, GO, funding | Whoever passes off the administrative part saves at your remuneration's expense – that's where several thousand francs lie |
Important for context: a single signal can have a harmless explanation. A provider showing three of them has none.
The three most expensive tricks in detail
The remote-diagnosis quote. The satellite image shows the roof area – not the brittle tiles, not the 1978 substructure, not the full meter cabinet. What would have been noticed on the site visit becomes "unforeseeable extra work" on the building site. Rule of thumb: no contract before an inspection – with us as with any specialist company, the site visit is part of the process.
The expiring promotional price. The classic of door-to-door and telephone marketing: the price is valid "only if signed today". The aim is to prevent quote comparison – because the offer doesn't survive it. Turn the tables: a provider whose price can't withstand comparison has already made the decision for you.
The warranty smokescreen. "25 years warranty" sounds reassuring – but on what? The module manufacturer's performance warranty covers gradual loss of output, not the inverter's failure and certainly not an installation error. Who bears what has to be in the quote; the breakdown belongs to the minimum technical information. And: a warranty is worth as much as the company behind it – see flag 7.
How to check in 15 minutes
1. Company check: commercial register entry (zefix.ch), registered office, active since when? Reference systems in your region that you can name and, if in doubt, visit? 2. Quote check: go through the items against our comparison checklist – missing items are questions, evasive answers are answers. 3. Process check: was there a site visit? Is the payment plan tied to construction progress? Are the connection request, Pronovo and GO registration expressly included? 4. Second quote: get at least one comparison quote – how to compare quotes fairly we've described separately.
The saddest calls we receive begin with "the system runs, but…": the salesperson is no longer reachable, the Pronovo registration was never made, the scaffolding was "not in the price", and nobody feels responsible for the warranty case. Strikingly often the same pattern lies behind it – contract signed at the kitchen table, under time pressure, without anyone ever standing on the roof. Our honest assessment: the damage almost never arises from bad modules – hardware is decent almost everywhere today. It arises from missing planning, missing items and missing people responsible. Exactly the three things you can check in a quarter of an hour before signing.
Frequently asked questions
Is a very low price automatically a warning sign?
No – but it's worth a question: where is the saving made? Sometimes the answer is legitimate (simple roof, standard components, lean structure), sometimes not (chain of subcontractors, missing items). The differences: cut-price providers vs. specialist companies.
May I withdraw from a signed solar quote?
For door-to-door sales and contracts initiated by phone, Switzerland provides a statutory right of withdrawal of 14 days; for quotes you obtained yourself, in principle not. When in doubt, act quickly and preserve the deadline in writing.
Are door-to-door and telephone salespeople inherently untrustworthy?
No – but the combination of cold calling, time pressure and closing a contract without a site visit is statistically the environment in which most problem cases arise. Have the quote left with you and review it in peace – a reputable provider has no problem with that.
What about offers of "free solar system" or rental models?
Behind those are contracting or rental models – not inherently untrustworthy, but the total cost over the term is practically always above purchase. Calculate the full costs over 20 years before signing "free".
How, conversely, do I recognise a reputable provider?
Site visit before the quote, complete technical details, a transparent payment plan, clearly regulated warranties, registrations included, references in the region – and composure at the sentence "I'll get a second quote as well".
Free initial consultation
The counter-design: a quote that withstands its own test.
Site visit, complete items, payment plan by construction progress, all registrations included – check us with our own checklist.
Want to calculate yourself first? Solar calculator with official roof data →
Prefer to talk? +41 78 830 83 35
Photovoltaic installer for your region →
Swissolar-certified specialist company · ESTI installation authorisation (Art. 14 NIV) · in Zurich since 2017 · over 150 systems completed · a personal answer from the specialist company, no call centre
Sources: Empirical data from installation practice; consumer-protection publications on door-to-door sales; CO (right of withdrawal for door-to-door sales).
Last updated: 9 July 2026 · Author: ecoEn editorial team
