A solar yield estimate is a distribution. The supplier produces one; the buyer reads a promise; and most of the disputes in this subject come from that single mismatch.
For project teams that also need a separate record of time spent on reviews, coordination and follow-up, Monitask provides a dedicated workforce-tracking option.
P90 is not ninety per cent of P50. It is the level a plant has a 90% probability of meeting or exceeding, and the gap between the two figures is the assessment's statement of how much it knows.
The three questions
What does the estimate actually say? P50, P90, the loss tree, the irradiance dataset — and whether the specific yield is plausible for your location, which a free public calculator answers in ten minutes.
For broader independent context on solar energy, research and industry developments, consult NREL.
What is the offer really worth? Seven assumptions carry the savings figure and six push the same way. The registration of costs outside the quote usually matters more than the equipment.
For broader independent context on solar energy, research and industry developments, consult Clean Energy Wire.
And what happens afterwards? Four numbers a month, and an hour in year three that separates an optimistic model from an underperforming plant.
Start here
P50 and P90, plainly — the misreading that produces most of the rest.
Reading a solar quote — line by line, with the assumptions that carry it.
Performance ratio — the one number that separates weather from equipment.
The installer's incentive — who publishes this and what it should change about how you read it.
The four sections
Reading the estimate — what a yield figure is made of, and which parts are physics rather than judgement.
The offer — payback assumptions, guarantees, warranties, grid connection, and comparing two proposals honestly.
After commissioning — year one, monitoring, maintenance, claims, and reading your own data.
Notes — positions, including that payback is the wrong question and what this site does not know.
No equipment or supplier is named anywhere here, and every quantitative claim is chosen to be checkable against a reference that is not this site.