What is the system
worth keeping?

Value for your decision

What did Jacquelyn or Andrew pay? Will you get your money back? What does this system save or earn? Those are practical questions about value. Fair market value for tax purposes serves a different purpose. Our approach draws on more than 20 years of real-world deals, from individual homes to large solar and storage portfolios and utility-scale projects.

Choose an existing-system benefit / buyout calculation or a new-system cash purchase comparison. New purchases use estimated first-year output and entered service lives; cash cost is deducted separately from benefits. Simple and discounted payback use year-end cash flows and must remain recovered through the modeled life. Financing, tax benefits and future resale proceeds are not assumed. Why we built Solar Blue Book.

Storage program context

Massachusetts: Clean Peak certificates, SMART storage adders and ConnectedSolutions have distinct eligibility and payment rights. Certificates may be assigned to a program sponsor. Connecticut: Energy Storage Solutions has enrollment and dispatch-performance incentives, with rules changing for new participants April 1, 2026. Confirm the installed system’s vintage, participation and remaining term. Do not add an initial installation discount again as future annual revenue or double count the same certificate/dispatch payment.

What this first version does

Some utilities buy all generation instead of crediting rooftop self-consumption. Where that published arrangement applies, the calculator loads its generation price separately from household electricity charges. Separate generation-meter fees reduce system benefits and are assumed unchanged by a PPA/lease buyout. If storage does not net against retail sales under that policy, energy dispatch, shifting savings and charging costs are not simulated; only entered net program payments, upkeep and meter costs are valued.

Some utilities retain a per-kWh charge on solar consumed in the home. That editable charge is deducted on direct solar use and solar sent into storage, including charging losses. It follows electricity-rate escalation. It does not apply to exports or grid charging and is assumed unchanged by a lease/PPA buyout.

Where solar-plus-storage enrollment adds a battery fee, that increment is separate from the base solar charge. The model stops each component at its entered asset life. These are planning assumptions; actual billing after retirement can differ. No fee is assigned to standalone storage from a rooftop-generation tariff.

Where a solar standby charge applies, enter its billed AC capacity separately from panel DC capacity. This cost reduces solar benefits over remaining solar life, using the cost-escalation assumption. For a PPA/lease buyout, the model assumes this utility charge stays on the homeowner bill before and after purchase, so it is not deducted again as a new ownership expense. Storage-only value assumes existing solar standby is unchanged.

Where the selected tariff has an explicit minimum energy bill, it appears as an editable billing floor. Solar and storage share the remaining savings above that floor; it is not added as a fixed fee. This annual approximation assumes equal monthly use/imports and a constant nominal minimum.

For tariffs with demand charges, enter average monthly billed peak demand separately from energy use. The bill context retains that charge; this annual model assumes no solar or storage reduction in billed peak demand. A blank demand entry means unknown, and the displayed bill subtotal excludes it.

No ancillary-services or storage-program revenue is assumed. Net annual storage payments default to $0. Enter only payments supported by your enrollment and rights; exclude certificates or dispatch revenue already included in another payment.

It discounts remaining annual benefits and costs back to today. Solar benefits are self-consumed electricity plus export credits, or the Buy-All payment. Additional incentives count only if you affirm you own them. Storage value is incremental: energy shifted after efficiency losses and foregone solar-export credits, plus entered net program payments, less upkeep.

The annual model limits battery use by capacity, power, reserve, available cycles, and household demand. Solar-charged storage is additionally limited by solar surplus. It is not an hourly dispatch simulation. Flat-rate grid charging can produce a negative benefit because charging losses cost money. Full-retail net metering can similarly make solar-to-battery shifting less valuable.

For a PPA or lease, the separate buyout comparison includes avoided payments during the remaining term, less ownership costs during that term. It excludes unverified transfers of incentives, post-contract ownership assumptions, financing, taxes, and a personal backup-power premium. A quote below this modeled amount is not a recommendation to buy.

The sensitivity range changes annual production / selected benefits by ±10%, upkeep and repair costs by ∓10%, and the discount rate by ∓2 percentage points (floor 0%). These are planning scenarios, not statistical bounds.

EIA state-average rate starting points: August 2026, released October 23, 2026. These averages include charges you may not avoid and are not your utility tariff. Replace them with the variable rate applicable to your bill. PVWatts can help estimate production if measured output is unavailable. DOE solar and storage explanation.

Model · calculator inputs stay local, except when you explicitly request the optional address lookup described above. No calculator inputs are sent to AI. A downloaded report is saved on your device. Contact collection and provider sharing remain off.