Start with price per watt, but do not stop there
A solar quote for a 10 kW system at $32,000 and one for a 6 kW system at $18,000 are hard to compare as lump sums. Price per watt normalises everything. Divide total price by system watts (system kW × 1,000): $32,000 ÷ 10,000 = $3.20/W and $18,000 ÷ 6,000 = $3.00/W. Now you're comparing apples to apples across different system sizes, states, and equipment tiers.
Why location and contract structure matter
Labor, permitting, interconnection, roof complexity, equipment, storage, and installer overhead vary by market. Financing can create an even larger difference: two proposals with similar monthly payments may have very different APRs, terms, dealer costs, and total scheduled payments.
A complete proposal is easier to verify
Ask every installer to state the exact equipment models, year-one production, assumed degradation, cash price, financing terms, roof work, interconnection scope, workmanship coverage, production guarantee, and exclusions. Wattcrunch flags missing fields because uncertainty hidden in a proposal often matters more than a small price difference.