The consultation is the moment when a reputable provider separates from a salesperson – and you steer it with your questions. Fifteen questions on roof, system, contract and service are enough to recognise depth of planning, honesty and willingness to serve. What matters is not just the answer, but whether it's concrete or evasive. (As of: July 2026)
Key points in brief
- A good consultation begins with listening and a site visit – not with a prepared closing offer.
- The most effective questions target the concrete: components by name, figures with assumptions, responsibilities with people.
- Four topic blocks cover everything: your roof and your consumption, the planned system, the contract – and service over the coming decades.
- Evasive answers are an answer in themselves: "brand quality", "we'll take care of it", "customary in the market" are non-statements.
- Take the questions with you in writing – reputable providers are glad about it, others get nervous.
Why the conversation decides more than the brochure
Brochures look good for every provider – modules gleam, returns glow, certificates adorn. What really makes a solar system a good or bad purchase over two decades is decided elsewhere: in the care of the planning, the honesty of the figures, and whether anyone picks up the phone in five years. Exactly these three things show up in the consultation – if you ask the right questions.
The common thread is simple: ask about the concrete. Every answer containing a name, a figure with its assumption or a named responsibility is a good sign. Every answer in the vague – "brand modules", "we'll take care of it", "customary in the market" – is worth a follow-up. How someone evades often reveals more than the topic itself.
Block 1: questions about your roof and consumption
Before the system is discussed, your house has to be discussed. Anyone who skips this block plans for the average instead of for you (why the site visit counts).
1. Were you on the roof – or are you planning from a satellite image? The answer separates planning from sales. Structure, tile condition and shading can only be seen on site. 2. How do you assess the condition of the roof skin and substructure? A system lasts 25–30 years – if a roof renovation is worthwhile beforehand, now is the moment. 3. How do you deal with shading? Trees, chimneys, neighbouring houses: the answer should name a concept (module layout, inverter choice), not soothing words. 4. How did you take my electricity consumption into account? System size and future demand (heat pump, EV) belong thought through together, not guessed.
Block 2: questions about the planned system
Now it gets technical – and this is exactly where it shows whether the quote is verifiable. These questions match the minimum technical information in a quote:
5. Which modules and which inverter – with type designation? Without names, no data sheet, no comparison, no warranty check. 6. How is the system sized – and why like that? The ratio of module to inverter output should be justified, not random. 7. What is the yield forecast based on? A serious figure names orientation, tilt and shading as assumptions – not a bare kilowatt-hour number. 8. What is included in the price – and what expressly is not? Scaffolding, electrical work, meter location, registrations: exclusions should be quantified. 9. Do you handle all registrations? Connection request, Pronovo, guarantee of origin, notification procedure, funding – several thousand francs of your remuneration hang on them.
Block 3: questions about contract and payment
The most beautiful plan is of little use without a clean contractual basis. This block protects you from the expensive surprises after the signature:
10. What does the payment plan look like? Instalments according to construction progress are customary in the industry – a high advance payment is a warning sign. 11. Which warranties apply – and who bears them? Product, performance and installation warranties are three different things with three debtors. 12. What happens with extra work on site? Fixed price or supplement by effort – and who decides what was "unforeseen"? 13. How binding is the date? A target date is normal, an empty promise is not.
Block 4: questions about service and the future
The system runs when the salesperson has long since moved on. This last block is the most often forgotten – and the most important for years 5 to 25:
14. Who comes when the inverter fails in six years – and within what time? The answer to this one question says more about the provider than any brochure. 15. Can I extend the system later – battery, wallbox? If planning is done today to be battery-ready (hybrid inverter, reserve space, empty conduits), that saves a multiple later.
How to classify the answers
You don't need any expertise to judge the quality of an answer – the tone usually gives it away by itself:
| Good sign | Warning signal |
|---|---|
| names concrete types, figures, names | "brand quality", "premium components" |
| explains the assumptions behind forecasts | gives only a single, round yield figure |
| quantifies exclusions openly | "we'll clarify that on site" |
| welcomes second quotes | pushes to sign "today" |
| has a named service organisation | "you're covered through the manufacturer" |
This classification doesn't replace a professional check – but it reliably filters whom you shortlist at all.
In the conversation we often notice after ten minutes whether a prospect ends up with us because they're unsure – or because they've already had two conversations and bring the right questions. The second group is our favourite, however paradoxical that sounds: anyone who asks about type designations, payment plan and the service case in year six forces no answer from us that we wouldn't give anyway – but they notice sooner that we give it. Our advice to everyone still at the beginning: ask every provider the same questions, us included. A conversation that can't withstand these fifteen questions saves you a contract that wouldn't have either.
Frequently asked questions
Do I have to be technically knowledgeable to ask the right questions?
No – the fifteen questions work without prior knowledge. You're not judging the technical answer itself, but whether it turns out concrete or evasive. Anyone can tell that.
How many consultations should I have?
At least two, better three – if only to be able to compare quotes fairly. Only in comparison does it show what an answer is really worth.
What if a provider takes my questions as distrust?
That is an answer in itself. A specialist company answers the fifteen questions routinely and often unprompted – irritation at follow-up questions is a warning sign.
Should I already close the deal with the first provider at the end of the conversation?
No. No serious offer expires within a few days; anyone pushing with "only valid today" wants to prevent comparison. Take the time a 25-year decision deserves.
Are the questions available to take away?
Yes – we provide the checklist together with our quote comparison aid, so you take the same yardsticks into every conversation.
Free initial consultation
Ask us these questions.
Free site visit, concrete answers with names and figures, all registrations included – check us with your own list of questions.
Want to calculate yourself first? Solar calculator with official roof data →
Prefer to talk? +41 78 830 83 35
Photovoltaics Switzerland – installation by a specialist company →
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 the consulting practice of ecoEn GmbH, Zurich region; Swissolar (recommendations on choosing a provider).
Last updated: 9 July 2026 · Author: ecoEn editorial team
