Most people getting solar quotes are comparing documents that don’t really line up. One is two pages and a price. Another runs to twelve pages with the important detail on page nine. A third quotes a bigger system for less money and doesn’t explain why.
You don’t need to be an electrical engineer to judge them. You need to know the handful of things that decide whether the system performs, and the gaps that should make you ask harder questions.
Start with the design, then the price
The most useful question to ask about any quote is: what consumption was this system sized against?
A properly designed quote will show that somebody looked at how you use electricity: your bills, your day/night split, when your load happens. One that wasn’t designed will just propose whatever fills the roof, or whatever hits a familiar price.
This matters because most of the value of a solar system comes from the electricity you use on site. Exported units are worth a good deal less than units you avoid buying. A system sized to your roof instead of your consumption can generate plenty and still pay back poorly.
If a quote arrived without anyone asking to see a bill, treat that as a warning sign.
Check that the equipment is named
Every quote should tell you, specifically:
- Panel: manufacturer, model, wattage per panel, and how many
- Inverter: manufacturer, model and rated output
- Mounting system: manufacturer, and whether it is specified for your roof type
- Battery, if included: manufacturer, model, usable capacity (not just nominal capacity)
“Tier 1 panels” is not a specification. Neither is “premium inverter”. Phrases like that leave the installer free to substitute, and that is exactly what you want pinned down before you sign.
On batteries, watch the difference between nominal and usable capacity. They are different numbers, and the usable figure is the one you’ll actually get.
Look for what is missing
Quotes mislead by leaving things out far more often than by getting things wrong. The usual gaps:
Scaffolding. On a two-storey house this is a real cost. If it isn’t mentioned, ask whether it’s included.
Electrical works. Does the price include any consumer unit upgrade, earthing or bonding work the installation needs? These sometimes turn up mid-job and get charged as extras.
Grid application and registration. Connecting a system means paperwork with the network operator. Someone has to do it. The quote should say who.
Grant handling. If the installer is applying on your behalf, the quote should say so. If you’re expected to do it yourself, you should know that before you sign.
Making good. Who repairs and reinstates anything disturbed during the install?
Roof access assumptions. Some quotes assume scaffold-free access that your site doesn’t allow.
The warranties are separate
People hear “25-year warranty” and assume it covers the whole system. It almost never does. There are normally three separate warranties from the manufacturers:
- Panel product warranty, covering the panel itself failing
- Panel performance warranty, guaranteeing the panel still produces a stated percentage of its original output after a given number of years
- Inverter warranty, usually much shorter than the panel warranties
Then there’s a fourth, and in practice it matters most: the installer’s own workmanship warranty, covering the installation itself. Panels rarely fail. Roof penetrations, cable runs and mounting are what cause problems, and those are the installer’s work, not the manufacturer’s.
Ask how long the workmanship warranty runs, and what happens to it if the company stops trading.
Inverters also have a shorter life than panels and should be expected to need replacing at least once over the life of a system. A quote that shows 25 years of operation with no inverter replacement is leaving a cost out.
Treat savings projections with care
Almost every quote has a savings or payback figure. These are the least reliable numbers in the document, because they rest on assumptions that are rarely written down:
- What unit rate was assumed, and does it go up over time?
- What export rate was assumed?
- What share of generation was assumed to be used on site?
- What annual degradation was applied?
- Was the inverter replacement cost included?
A projection is only as good as those inputs. If they aren’t written down, the figure is decoration. It’s entirely reasonable to ask an installer to show you the assumptions behind their number. If they can’t, that tells you plenty.
Check the installer as well as the quote
For a domestic grant you need an SEAI-registered installer, and electrical work in Ireland must be done by a registered electrical contractor. You can check both yourself, and you should, instead of trusting a logo on a PDF.
Beyond registration, ask:
- Who does the work, employed crews or subcontractors?
- Who do you ring in three years if something stops working?
- How long has the company been trading under its current name?
Aftercare is where installers differ most, and you can’t see it at the point of sale.
Questions to ask
If you take nothing else from this, take these:
- What did you size this system against?
- What share of the generation do you expect us to use on site?
- Is scaffolding included?
- What electrical works are included, and what would be charged as an extra?
- How long is your workmanship warranty?
- Who handles the grant application and the grid paperwork?
- What happens if the survey finds something the quote didn’t allow for?
Any competent installer will be comfortable answering all seven. If a quote gets vague under those questions, you’ve learned something useful before committing to anything.
If you’d like a quote laid out this way, with the design reasoning and the assumptions written down, get in touch. We’ll also happily read through a quote you’ve had from someone else and tell you what we’d ask about it.