How to Compare Solar Quotes — Step-by-Step

Step 1 — Collect at least three quotes

Before you can compare anything, you need a baseline. One quote gives you a number. Two quotes let you spot a difference. Three quotes let you identify a pattern and an outlier.

When requesting quotes, give every installer the same brief: the same approximate system size (or monthly usage in kWh), the same roof details, and the same question — ask for a fully itemised quote with all exclusions listed. Standardising the input makes the outputs comparable.

Request quotes in writing (PDF or email), not verbal. A verbal quote is worthless for comparison and provides no protection if the final invoice looks different.

Step 2 — Normalise the scope before comparing prices

This is the most commonly skipped step and the most important one. A solar installation quote is not just a product price — it includes (or excludes) a range of services and components that vary significantly between installers.

Before comparing any prices, check whether each of the following is explicitly included or excluded in every quote:

• • Transport and delivery — moving heavy panels, racking, and inverters to site
• • Earthing and surge protection — mandatory safety requirement in most countries
• • AC/DC isolators and distribution boards (ACDB/DCDB)
• • Cabling — DC string cable from panels to inverter, AC cable to switchboard
• • Switchboard upgrade — if your existing board cannot accept the solar connection
• • Net metering / interconnection application — utility fee to register your export
• • Permits and electrical inspections
• • Scaffolding or elevated access equipment — for multi-storey or steep-pitch roofs
• • Monitoring hardware and app subscription
• • Commissioning, testing, and handover training

A quote that excludes transport, earthing, and permits can look 15–25% cheaper while actually costing the same or more once those line items are added back. Add the estimated cost of any excluded items to each quote before comparing the totals.

Step 3 — Compare the solar panels

Solar panels are not interchangeable commodities. Check each of the following for every quote:

• • Brand and full model number — search the model on the manufacturer's website to verify it exists and match the specs. Budget installers sometimes quote non-existent or discontinued models.
• • Wattage (Wp) per panel — higher Wp is generally better but verify against the efficiency claim.
• • Technology — PERC is the current mainstream; TOPCon offers higher efficiency and lower degradation; HJT is premium. A cheaper PERC panel may produce less power over 25 years than a more expensive TOPCon.
• • Efficiency (%) — how much of the available sunlight the panel converts to electricity. Higher efficiency means fewer panels needed for the same output, useful for space-constrained roofs.
• • Product warranty — typically 10–15 years covering manufacturing defects. Shorter is a risk signal.
• • Performance warranty — the industry standard is ≥80% of rated output after 25 years. Some premium panels guarantee 87–90%. Read the actual percentage, not just the years.
• • Annual degradation rate — typically 0.5–0.7%/year. Lower is better for long-term output.

Step 4 — Compare the inverter

The inverter converts DC power from the panels into AC power your home can use. It is the most electronically complex component and statistically the most likely to need replacement during the system's 25-year life.

• • Type — on-grid (grid-tied, no battery support), hybrid (battery-ready), or off-grid. Hybrid costs more upfront but avoids a full replacement if you add batteries later.
• • kW rating vs array size — the inverter's AC output rating should be appropriately sized to the panel array's DC capacity. An undersized inverter clips output on sunny days; an oversized one wastes money.
• • MPPT inputs — multiple MPPT channels let the inverter handle panels on different roof orientations or with partial shading independently.
• • Brand reputation and local support — inverters from brands with local distributor support are significantly easier to warranty-claim or replace.
• • Warranty period — typically 5–10 years standard. Some brands offer extended 10–12 year warranty for a fee. Factor this into the total cost.

Step 5 — Compare the battery (if included)

Battery storage is the area where misleading specifications are most common. The key points:

• • Usable kWh vs nominal kWh — always ask for usable capacity. A "10 kWh" battery at 90% depth of discharge gives 9 kWh usable. At 80% DoD it's 8 kWh. Some quotes list nominal without clarifying DoD — this is a deliberate or careless omission.
• • Chemistry — LFP (lithium iron phosphate) is the current standard for home storage: safer (no thermal runaway risk), longer cycle life, wider temperature tolerance. NMC (lithium nickel manganese cobalt) is older and carries higher risk. Avoid quotes that don't specify chemistry.
• • Cycle life — how many full charge/discharge cycles the battery will complete at rated capacity. LFP typically 3,000–6,000 cycles. At one full cycle per day, 3,000 cycles is ~8 years.
• • C-rate — the discharge rate relative to capacity. A 1C battery can discharge its full capacity in one hour. Lower C-rates limit backup power for high-draw appliances.
• • Warranty — look for both years and cycle count. "10 years or 4,000 cycles, whichever comes first" is a standard form.

Step 6 — Check warranties end-to-end

A complete solar installation requires four separate warranties to be fully covered:

1. Panel product warranty — covers manufacturing defects. Typically 10–15 years.
2. Panel performance warranty — guarantees minimum output over 25 years.
3. Inverter warranty — covers the electronics. Typically 5–10 years.
4. Battery warranty — covers cells and BMS. Typically 5–10 years or cycle count.

Additionally, check the installer workmanship warranty — this covers the installation work itself (roof penetrations, mounting, wiring). Industry standard is 5–10 years. A budget quote with a 1-year workmanship warranty is a significant risk, particularly for roof integrity.

Verify that the warranty provider is the manufacturer or a creditworthy insurer — not just "the installer guarantees it" verbally. If the installer goes out of business in year 3, a verbal workmanship guarantee is worthless.

Step 7 — Evaluate the installer's credentials

The equipment is only as good as the installation. A misaligned panel string, undersized cable, or poor roof penetration can cause performance loss, safety hazards, or voided warranties. Check the following:

• • Accreditation / certification — CEC accreditation (Australia), MCS certification (UK), NABCEP certification (US), MNRE empanelled installer (India).
• • Insurance — public liability and workers' compensation. Ask for a certificate.
• • Years in business and local references — an installer who has been operating in your area for 5+ years with verifiable local references is lower risk than a new entrant.
• • Post-installation support — who do you call if the monitoring shows degraded output in year 4? Is there a local service team?

Step 8 — Calculate full-scope cost per kW

Once you have added back all excluded items to each quote (step 2), divide the adjusted total by the system size in kW. This gives a full-scope cost per kW figure that makes quotes directly comparable regardless of system size differences.

Example: Quote A is ₹3,20,000 for 5 kW = ₹64,000/kW. Quote B is ₹2,80,000 for 5 kW but excludes earthing (₹8,000), net metering (₹5,000), and transport (₹4,000) = true cost ₹2,97,000 = ₹59,400/kW. Quote B is cheaper on adjusted cost-per-kW even though Quote A's headline price looked lower — but only if the equipment quality is equivalent.

Sort your adjusted quotes by cost-per-kW, then layer in the equipment quality differences. The cheapest per-kW quote with equivalent equipment and credentials is the starting point for your decision — not the cheapest headline number.

Step 9 — Verify equipment claims independently

Before signing anything, take 10 minutes to verify:

• • Search the panel model number on the manufacturer's website — does the spec sheet match what the quote says?
• • Check whether the panel is on your country's approved product list (CEC approved, ALMM listed in India, MCS certified in the UK).
• • Search the inverter model on the manufacturer's site — does it match the kW rating quoted?
• • For batteries, check the datasheet for the exact usable kWh and cycle life figure — not what the installer wrote in the quote.

Solar Padtal automates this step — we cross-reference quoted equipment specs against manufacturer databases and flag any mismatches or unverifiable models.

Step 10 — Assess payback period and ROI

A solar installation is an investment, and the payback period is the most useful single metric for comparing value — how many years until the energy savings repay the upfront cost.

Calculate it simply: adjusted total cost ÷ annual bill savings = payback years. Annual savings depends on your usage (kWh/month), your tariff rate, and your self-consumption ratio (how much of the solar generation you use directly vs export). Typical residential payback ranges from 4–7 years in Australia and India, 6–10 years in the UK and Germany, and 5–8 years in the US.

Be cautious of payback calculations provided by the installer — these often use optimistic assumptions about future tariff increases, self-consumption, and system performance. Use a conservative estimate and treat the result as a range, not a precise figure.

Frequently asked questions