Why solar quotes vary
If three companies measured the same roof and still disagreed, you are usually comparing different spreadsheets, not different physics.
Same roof, different math
Think of each quote as a bundle of assumptions. Small changes in inputs can swing system size and price without anyone being dishonest.
Quote A
8.4 kW
Higher usage guess
Quote B
7.2 kW
Conservative shade model
Quote C
9.1 kW
Different setback layout
Factors that move the number
- Annual usage estimate
If one proposal uses a higher kWh/year guess, system size and price move even when the roof is the same.
- Roof model & shading
Different shade tools, setback rules, and fire paths change panel count and string layout.
- Battery size & backup goal
Partial backup vs whole-home ambition changes inverter and battery stack, and sometimes the main panel work.
- Cash vs finance & dealer fee
“Low monthly” often hides dealer fees and total interest. Cash price and financed price are not the same comparison.
- Electrical upgrades
One bid may assume a main panel swap or service upgrade; another may omit it until later, then the price jumps.
What to do next
Use the 60-second $/W benchmark for a fast band from a few numbers, or full quote audit to paste a proposal and get questions before you sign. Read the flagship guide: Why three quotes, three sizes.
Local context examples: compare the Amherst guide for tree-shade and EV stacking issues and the Williamsville guide for larger-home sequencing and multi-panel scope.
FAQ
Is one quote automatically lying if the kW differs?
Not necessarily. Assumptions differ. The job is to surface which inputs moved (usage, shade, setbacks, equipment, financing, electrical scope).
Should I just pick the middle price?
Price without scope is meaningless. A cheaper quote that omits panel work can become the most expensive project after change orders.