Chief Appraiser Says
Reading the actual guideline text below — never a general AI guess
Here's what the guidelines say about solar panel types, inverters, batteries, and typical installed costs:
We have three main inverter choices: a string inverter (cheapest upfront, but one shaded panel can drag down the whole system's output) works best on simple unshaded roofs; microinverters (one small inverter at each panel, eliminating shading problems and offering panel-level monitoring) cost more upfront but typically come with the longest warranties, around 25 years; and power optimizers (a middle ground that puts a DC optimizer at each panel feeding into one central inverter) solve most shading issues without microinverter costs. For batteries, nearly all residential storage sold today is lithium-ion, with LFP (lithium iron phosphate) accounting for roughly 90% of new annual additions due to superior thermal stability, longer cycle life, and lower cost compared to the older NMC chemistry, while lead-acid batteries are legacy technology found mostly in older off-grid systems with much shorter usable life. The passages identify that typical installed costs exist for solar panels but do not provide the actual cost figures themselves.
Straight from Solar PV: Components & Typical Installed Costs (NREL, LBNL, EnergySage, BloombergNEF) — nothing added.
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© Copyright Notice: © 2026 Fannie Mae. Excerpts shown for research and reference only. Full document available at selling-guide.fanniemae.com. Reproduction restricted to Fannie Mae-approved lenders.
© Copyright Notice: © Freddie Mac. Excerpts shown for research and reference only. Full document available at guide.freddiemac.com. Reproduction restricted per Freddie Mac copyright policy.
© Copyright Notice: © Fannie Mae. UAD 3.6 / URAR reference materials shown for research and reference only. Full documents available at fanniemae.com/uad. Reproduction restricted per Fannie Mae copyright policy.
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than typical home rooftops. Bifacial panels, which capture light from both the front and back of the panel, add measurable output in ground-mount or elevated installations with…
Solar PV: Components & Typical Installed Costs (NREL, LBNL, EnergySage, BloombergNEF) · Solar_PV_Components_and_Typical_Costs.txt · Page 2
than typical home rooftops. Bifacial panels, which capture light from both the front and back of the panel, add measurable output in ground-mount or elevated installations with reflective surroundings, but the benefit is much smaller on a standard flush roof mount. Inverter types. An inverter converts the direct current (DC) electricity panels produce into the alternating current (AC) electricity a home actually uses, and the choice of inverter architecture is one of the bigger cost and performance decisions in a system design. A string inverter connects a series of panels to one central unit; it's the lowest-cost architecture, but one shaded or underperforming panel can drag down the output of the entire string, so it works best on simple, largely unshaded roofs. Microinverters place a small inverter at each individual panel, eliminating that shading penalty and providing panel-level production monitoring, at a higher upfront equipment cost; manufacturers typically back microinverters with the longest warranties in the industry, commonly around 25 years. Power optimizers pair a DC optimizer at each panel with a single central inverter, conditioning each panel's output individually before it reaches the shared inverter — a middle-ground architecture that solves the worst of string inverters' shading problem without the full cost of microinverters at every panel. Hybrid inverters combine a solar inverter and a battery inverter in a single unit, managing solar production, battery storage, and grid interaction together, and are the typical choice for homeowners who want to keep a future battery addition simple even if they aren't installing one immediately. Battery chemistry. Nearly all residential battery storage sold today is lithium-ion, and within that category the market has shifted decisively toward one chemistry. Per BloombergNEF's global energy storage market tracking, LFP (lithium iron phosphate) batteries account for roughly 90% of new annual lithium-ion storage capacity additions, driven by superior thermal stability, a longer cycle life, and a cost advantage over the alternative. NMC (nickel manganese cobalt) batteries, the older residential storage chemistry, are being phased out of home energy storage in favor of LFP, though NMC remains more common in electric vehicles where its higher energy density per unit of weight matters more than it does for a battery sitting in a garage or utility closet. Lead-acid batteries are a legacy technology found mostly in older off-grid systems, with a much shorter usable life than either lithium chemistry. Typical installed cost for solar panels. Two respected
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density per unit of weight matters more than it does for a battery sitting in a garage or utility closet. Lead-acid batteries are a legacy technology found mostly in older…
Solar PV: Components & Typical Installed Costs (NREL, LBNL, EnergySage, BloombergNEF) · Solar_PV_Components_and_Typical_Costs.txt · Page 3
density per unit of weight matters more than it does for a battery sitting in a garage or utility closet. Lead-acid batteries are a legacy technology found mostly in older off-grid systems, with a much shorter usable life than either lithium chemistry. Typical installed cost for solar panels. Two respected national data sources currently show somewhat different figures, and the difference itself is informative: Lawrence Berkeley National Laboratory's "Tracking the Sun" report, a Department of Energy national laboratory study drawing on a broad sample of actual installed systems, puts the national median cash-purchase price in a roughly $3.10-$3.50 per watt range. EnergySage's 2026 marketplace data, which reflects competitively-bid quotes from installers on its own platform, shows a lower average of roughly $2.60 per watt, translating to about $31,135 for a 12kW system before any incentives. The gap between the two is a reasonable, honest one: EnergySage's sample reflects installers actively competing for a homeowner's business through its marketplace, while LBNL's broader sample captures a wider range of deals, including ones that never went through competitive bidding. Neither number is "the" price for a specific roof — actual bids vary by market, roof complexity, and which of the equipment choices above a homeowner selects. What that price is typically made of: equipment (panels, inverter, racking, wiring) generally represents 40%-50% of the total; labor and installation make up a meaningful share of the remainder; and soft costs — permitting, interconnection fees with the utility, system design, and sales overhead — are often the most underestimated piece of the total price, and a large part of why cost per watt doesn't fall in a straight line as system size grows. A larger system spreads those same fixed soft costs over more panels, which is why, for example, a 10kW system typically costs closer to 1.7 times a 5kW system rather than a full 2 times as much. Typical installed cost for battery storage. EnergySage's 2026 marketplace data puts the average installed battery cost at roughly $1,037-$1,128 per kWh of usable storage, with a wide range depending on brand and installation complexity — from around $651/kWh on the low end to roughly $1,510/kWh on the premium end. A common whole-home backup configuration uses a 13.5 kWh battery, which works out to approximately $15,228 installed before incentives at the marketplace average price. Homes seeking true whole-home backup, including heating and cooling loads, often need two
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same market, to extract what buyers are actually paying for it. Lawrence Berkeley National Laboratory's peer-reviewed "Appraising into the Sun" study is the leading public…
Solar PV: Real vs. Personal Property & Valuation (Fannie Mae, Freddie Mac, FHA, VA, UAD 3.6) · Solar_PV_Real_vs_Personal_Property.txt · Page 4
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same market, to extract what buyers are actually paying for it. Lawrence Berkeley National Laboratory's peer-reviewed "Appraising into the Sun" study is the leading public research supporting this method, and found that paired-sales results and cost/income-based estimates tend to converge when both are done carefully — but the guidance is clear that cost and income approaches can only support a market-based adjustment, never substitute for one. What this means for appraisers. Before assigning any value to a solar installation, confirm ownership documentation exists and is unambiguous — don't assume based on appearance. Where value is supported, build the adjustment from paired sales in the local market wherever comparable data exists, using cost or income evidence only as a supplement, never as the sole basis. Document the ownership status explicitly in the Energy Efficient & Green Features section as UAD 3.6 requires, and note leased or PPA systems as personal property present on the property without folding their value into the sales comparison grid. If a battery is also installed. Home battery storage is increasingly sold alongside solar panels, and the same ownership-based rule described above governs a battery exactly the way it governs the panels themselves: an owned or fixture-financed battery can be considered for contributory value under the same standard appraisal requirements, while a leased battery or one tied to a separate financing agreement that allows repossession is personal property and must be excluded, regardless of how permanently it appears to be wired into the home's electrical system. The practical complication is that battery attachment to solar systems is newer than solar panels themselves, and because far fewer home sales involve a confirmed owned battery than involve confirmed owned panels, the paired-sales market data an appraiser or agent would need to isolate a battery's own distinct contribution to price is considerably thinner than the data available for panels alone. That doesn't change the ownership rule — it just means an appraiser is more likely to find solid market support for a solar panel adjustment than for a battery-specific one in most markets today, and an agent should set expectations with a seller accordingly rather than assuming a battery adds a comparable, well-documented premium the way an owned solar array increasingly does. What this means for real estate agents preparing a listing. Determining whether solar panels add value to a specific house, and by how much, is appraisal work —