How to Read Solar Proposals and Quotes: What to Look For (and What to Watch Out For)

Most homeowners receive a solar proposal and have no idea how to evaluate it. The numbers look impressive, the savings projections are compelling, and the salesperson seems confident. But proposals from different companies for the same roof can vary wildly — in price, in projected production, in equipment quality, and in what assumptions are baked into the savings numbers.

This guide gives you the framework to read any solar proposal critically — so you know what questions to ask and what red flags to watch for before you sign anything.

I'm Dave Simmer, a NABCEP-trained solar designer based in Scituate. I've been reviewing proposals and designing systems on the South Shore since 2011. Here's what I look at.

Start here: the five numbers that matter most

1. System size (kW)

The system size tells you the total generating capacity being proposed. Make sure it's actually appropriate for your usage (find out what size solar system do I need?). Divide your annual electricity consumption (in kWh, from your electric bills) by 1,200 — that gives you a rough target system size in kW for a Massachusetts location. If the proposed system is significantly larger or smaller than that number, ask why.

2. Projected annual production (kWh)

This is the estimated electricity your system will produce each year. It should be close to your actual annual electricity consumption (see how to calculate your solar savings). If projected production is 30% higher than your usage, you're likely being sold an oversized system. If it's 40% lower, you're being undersold. Both are problems.

3. Cost per watt

Divide the total system cost by the system size in watts. A 10 kW system at $33,000 is $3.30/watt. This is the best apples-to-apples comparison metric across proposals of different sizes. In Massachusetts in 2026, a competitive residential install is roughly $3.00–$3.75/watt before incentives.

4. Payback period

A realistic payback period for a well-designed Massachusetts system is 5–9 years (read is solar worth it in Massachusetts?). If a proposal shows a 3-year payback, scrutinize every assumption carefully. If it's showing 12+ years, something is off — either the system is poorly designed or the savings projections are too conservative.

5. Year 1 savings vs. Year 1 loan/lease payment

If you're financing, the proposal should show your estimated Year 1 electricity savings alongside your Year 1 payment. For the math to work in your favor, savings should be in the same ballpark as — or exceeding — your monthly payment. If the payment is significantly higher than the savings, understand why before you sign.

What to look for in the production estimate

Production estimates should be based on your actual roof — not a generic formula. Ask how the estimate was calculated. Quality proposals use software like Aurora Solar or PVWatts that accounts for your specific roof orientation, pitch, shading, and local solar irradiance data for your area.

Be cautious of production estimates that seem optimistic. Some companies inflate production projections to make the payback period look better. If a company is projecting 15% more production than another company for the same roof and system size, ask them to explain the difference.

What incentives are factored in — and are they accurate?

Most proposals show a "net cost after incentives" number. Make sure you understand exactly which incentives are included and whether they're accurate (see the full Massachusetts solar incentives guide).

For Massachusetts homeowners in 2026:

• The federal ITC has expired and should not be included
• The $1,000 Massachusetts state tax credit is real and applicable
• The sales tax exemption is real — no 6.25% sales tax on equipment
• SMART payments are real but modest (~$0.03/kWh over 10 years)
• Net metering credits are real and significant

If a proposal is factoring in a federal tax credit that no longer exists, that's a serious problem — either the company isn't current on policy or they're inflating the incentive stack to make the net cost look lower. Check what incentives are still available in 2026.

Equipment: what are you actually getting?

Solar panels

The proposal should specify the panel manufacturer, model, and wattage. Look up the panel's specifications and warranty. Quality panels carry 25-year product and performance warranties. Performance warranties typically guarantee that the panel will still produce at least 80–90% of its rated output after 25 years.

Be cautious of proposals that list generic "Tier 1" panels without specifying brand and model. You deserve to know exactly what's going on your roof.

Inverters

The inverter converts DC electricity from your panels to AC electricity your home uses. The two main types are string inverters and microinverters. Microinverters (like Enphase) are installed on each panel individually, which improves performance in partial shading and makes system monitoring easier. String inverters are less expensive and perform well on unshaded roofs. The proposal should specify which type and what brand. Read Enphase vs. SolarEdge — which is right for your roof?

Racking and mounting

The racking system is what attaches your panels to your roof. It should be from a reputable manufacturer and appropriate for your roof type. Cheap racking is a long-term problem — your panels are going to be up there for 25+ years through New England winters.

Red flags to watch for

• Production estimates that don't reference your actual roof and actual usage
• Federal tax credit included when it no longer applies
• Payback periods under 4 years without a clear explanation of assumptions
• Equipment listed generically without brand and model specifics
• No mention of SMART enrollment process
• High-pressure sales tactics or artificially short quote expiration windows
• Savings projections that assume electricity rates will rise at 5–6% per year — while rates have risen, aggressive escalator assumptions inflate 25-year projections significantly

The bottom line on evaluating proposals

A good solar proposal is transparent about its assumptions, specific about its equipment, realistic about its projections, and honest about what you're actually getting for your money. If something feels off — if the savings seem too good, if the equipment isn't specified, if the net cost depends on incentives that don't apply — trust that instinct and ask questions.

I'm always happy to review a proposal you've received from another company and give you an honest read on whether it makes sense (or get an estimate from Solar Dave). No sales pitch, no pressure — just a second set of experienced eyes.

Already have a quote in hand? I'll review it line by line — see my Compare a Solar Quote tool.

Frequently Asked Questions