Commercial solar proposals are easy to compare on price and hard to compare on substance. These five questions surface the difference.
Ask every contractor the same five. The answers tell you more than the bottom-line figures do.
1. What portion of this system’s annual production will my building consume on site?
This is the single most revealing question you can ask, and many proposals cannot answer it.
Under California’s Net Billing Tariff, electricity your building uses is worth the full retail rate you avoid paying. Electricity exported to the grid earns avoided-cost value instead — and midday exports, which is when a solar array has surplus, earn among the lowest values in the schedule.
A contractor who sized the system to your load will have this number ready. A contractor who sized it to your roof will not. If the answer shows heavy export and the savings model still credits those exports at retail value, the payback figure on the cover page is not achievable.
2. What is this sizing based on — and did you use interval data?
Twelve monthly totals tell you how much electricity you used. Interval data tells you when, which is what actually determines the right system size.
If nobody asked you for interval data, nobody modeled your load shape.
3. Does this project require a utility service upgrade?
If your existing electrical service cannot accommodate the new generation, an upgrade carries its own engineering, its own cost, and its own place in the utility’s queue. It is frequently the longest single item in a project.
You want this identified before you sign, not discovered in month three. Ask directly, and ask what the timeline looks like if the answer is yes.
4. Who actually performs the installation?
Many solar companies sell the job and subcontract the work. That is not automatically bad, but it changes who is accountable when something needs correcting, and it changes who you are dealing with in year four.
Ask who will be on your roof, who holds the license, and who you call for warranty service.
For our part: our own team completes the installation. We never subcontract the job to others.
5. What does the warranty actually cover, and for how long?
There are two separate warranties and they are easy to conflate.
- Workmanship — the installation itself, covered by the contractor.
- Equipment — provided separately by each manufacturer. Panels typically carry a product warranty of roughly 10 to 15 years and a performance warranty of 25 to 30. Inverters generally run 12 to 15 years, with extended coverage available from most manufacturers.
Extended inverter coverage is often worth considering. Inverters run continuously under real thermal stress, and their high-power electronics age. Ask what is recommended and why — the reasoning should come from field experience, not from a brochure.
A Bonus Question
If the proposal includes battery storage, ask what specific problem the battery solves in your building, and ask to see the interval data that shows the problem exists.
For a daytime commercial operation, the answer is sometimes genuine — demand charges that do not coincide with production, significant evening load, or an outage that would cost you real money. Often it is just in the template.
Request a free consultation and put these questions to us.