Field manual · Prices verified November 2026
When the street goes dark, your house doesn't have to.
A working primer on residential and small-business microgrids and nanogrids: what each component does, how to size it, what it costs in 2026, and how long it actually keeps the lights on.
01 · Basics
Microgrid, nanogrid, or just a battery?
The National Electrical Code defines a microgrid as an electric power system that can operate in island mode, with interconnected loads and energy sources that can disconnect from and reconnect to the utility [32]. The defining capability is not the solar panels. It is the ability to island: open a connection to the grid, keep your own loads running from local sources, then resynchronize safely when utility power returns.
A plain grid-tied solar system cannot do this. Under IEEE 1547 and UL 1741, grid-tied inverters must stop exporting when the grid fails so line workers are not energized by your roof [33]. Islanding requires three additions: storage or a generator to form the grid locally, an inverter able to run in grid-forming mode, and a transfer device that isolates your building.
A nanogrid is the same idea at the smallest scale: one building, one owner, usually one inverter bus feeding a set of backed-up circuits. Most home battery installations are nanogrids in practice, even if marketed as whole-home microgrids.
Nanogrid
One battery or hybrid inverter backing critical circuits: refrigerator, lights, network, furnace blower, medical devices. Often a single 10–15 kWh LFP unit.
Residential microgrid
Whole-home backup with multiple sources (PV, two or more batteries, optional standby generator or EV), a microgrid interconnect device and load management to shed big appliances.
Small-business microgrid
Often three-phase service, a commercial ATS or switchgear, refrigeration and point-of-sale as critical loads, and demand-charge management as a second revenue line.
Four operating states every system must handle
- AGrid-parallel. Solar serves loads first, charges the battery, and exports surplus under your utility interconnection agreement.
- BTransition. The grid drops. The transfer device opens within milliseconds to seconds and the inverter becomes the voltage and frequency reference.
- CIslanded. Loads run from battery and solar, with a generator or EV as a reserve. The energy management system sheds non-critical loads to stretch runtime.
- DResynchronization. When stable utility power returns, the system matches voltage, frequency and phase before closing back onto the grid, per IEEE 1547 timing rules.
02 · Architecture
Watch the energy move
Switch operating modes to see how power flows through a typical AC-coupled home microgrid. Select any component for a plain-language explanation.
Swipe sideways to see the full diagram.
03 · Core components
What each box does, what to ask, what it costs
Solar PV array
Panels produce DC power whenever light hits them. In a microgrid, the array is the only source that refills the battery during a long outage, so its size sets how many days you can ride through, not just how much you save.
A useful rule of thumb: each kilowatt of array produces roughly peak sun hours × 0.8 kWh per day after wiring, heat and inverter losses. In northern Virginia, at about 4.3 peak sun hours, a 10 kW array averages roughly 34 kWh a day, far less in December.
Questions for your installer
- Microinverters, string inverter with optimizers, or DC into a hybrid inverter? This determines whether the array keeps producing when the grid is down.
- What is the shading-adjusted production estimate by month, not just annually?
- Does the rapid-shutdown solution (NEC 690.12) work during islanded operation?
2026 price markers
- Median quoted price, H1 2026
- $2.57/W [1]
- Median system (~12 kW) before incentives
- $30,712 [1]
- Texas state median
- $2.00/W [2]
- Illinois state median
- $3.07/W [2]
- National benchmark (SEIA/WoodMac)
- $3.36/W [3]
- 4 kW system average
- $3.64/W [4]
- 10 kW system average
- $2.86/W [4]
Homeowners lost the 30% 25D credit for systems finished after December 31, 2025 [5][6].
Battery storage: lithium iron phosphate vs. solid-state
For any system you can buy and permit in 2026, the answer is lithium iron phosphate (LFP). Solid-state batteries are real in laboratories and early EV programs, but there is no mainstream, UL 9540-listed solid-state home storage product to design around today [14]. Industry analysts expect residential solid-state around 2030 or later, at two to three times LFP cost at introduction [15].
| Attribute | LFP (LiFePO₄) | NMC | Semi-solid | Solid-state |
|---|---|---|---|---|
| 2026 status | Mainstream Powerwall 3, Enphase 10C, FranklinWH aPower 2 [9][11] | Legacy Older home units; dominant in EVs | Niche A few home products [16] | Not available No mainstream stationary product [14] |
| Thermal stability | High; resists thermal runaway | Lower; needs more fire mitigation | Improved over liquid cells | Expected best (non-flammable electrolyte) |
| Cycle life / warranty | 6,000+ cycles; 10–15 yr warranties [11] | Typically fewer cycles | Vendor-specific | Unproven in stationary use |
| Pack cost (BNEF 2025) | $81/kWh [13] | $128/kWh [13] | — | — |
| Installed home cost | $700–1,300/kWh [12] | Similar or higher | 40–80% premium [16] | 2–3× LFP at launch (projected) [15] |
| Energy density | Lower (fine when weight doesn't matter) | Higher | Higher | Highest |
| Best use today | Default choice for homes and small business | Replacement for existing NMC systems | Pilots with tight space limits | Watch list; plan a future retrofit path |
What the numbers on the spec sheet mean
- Usable kWh is energy; continuous kW is how many appliances can run at once. A Tesla Powerwall 3 stores 13.5 kWh and delivers 11.5 kW continuous [9].
- Surge / locked-rotor amps decide whether a well pump or central AC can start. Ask for a soft-start kit on compressors.
- End-of-warranty capacity (often 70% at 10 years) tells you what you will have in a decade [9].
- UL 9540 and UL 9540A: the system listing and the fire-propagation test report your fire marshal will ask for [29][30].
2026 price markers
- Tesla Powerwall 3, typical installed
- $13,473 [9]
- Average battery install, H1 2026
- $15,650 [34]
- Powerwall expansion unit
- ~$5,900 [10]
- Stationary pack price drop, 2025
- −45% to $70/kWh [13]
Falling pack prices have not fully reached installed prices; labor, permitting and electrical work are most of the bill.
Bi-directional (hybrid) inverters
The inverter is the brain of the island. A bi-directional unit converts DC to AC for your loads and AC back to DC to charge the battery. In an outage it becomes grid-forming: it sets voltage and frequency for the whole house.
AC-coupled vs. DC-coupled
- AC-coupled: the battery has its own inverter and sits beside an existing solar inverter. Easiest retrofit; small round-trip loss from converting twice. Most all-in-one home batteries work this way.
- DC-coupled (hybrid): panels and battery share one inverter. Higher efficiency, one box to service, popular in new builds and off-grid-capable systems.
Listings that matter
Look for UL 1741 SB with IEEE 1547-2018 grid-support functions, required by many utilities for new interconnections [33]. Confirm the continuous kW, surge rating and whether 120/240 V loads stay balanced in island mode.
Automatic transfer switches and islanding devices
Something has to physically separate your building from the utility before your batteries energize the wiring. There are three common approaches:
- Automatic transfer switch (ATS): a proven, often 200 A service-rated switch. Common with standby generators; can be paired with batteries.
- Microgrid interconnect device (MID) / backup gateway: a smart switch with metering that coordinates solar, battery and generator. NEC 705 Part II covers microgrid systems and MIDs [32].
- Critical-loads subpanel: move only essential circuits to a backed-up panel. Cheapest, but every circuit change is an electrician visit.
NEC 2023 article 706.15 requires an outdoor, readily accessible emergency shutdown for energy storage at one- and two-family dwellings [31]. UL 3010, a standard aimed at microgrid interconnect equipment, is still in development [32].
Home energy management systems
A HEMS decides what runs when. During normal operation it shifts EV charging and water heating to cheap or sunny hours. During an outage, it is what turns a 13.5 kWh battery from a six-hour stopgap into a two-day bridge, by shedding the dryer, oven and EV charger automatically.
- Monitoring only (circuit-level CT clamps such as Emporia Vue): visibility, no control.
- Load controllers (e.g. Lumin): add remote relays to an existing panel.
- Smart panels (e.g. SPAN): replace the main panel with app-controlled breakers that integrate with batteries.
Smart load control can also let you avoid a costly service upgrade, because the system caps simultaneous demand.
Standby generators and vehicle-to-home
Batteries handle the first night. A fuel source handles the fifth cloudy day. A small natural-gas or propane generator that only tops up the battery runs far fewer hours than one carrying the whole house.
Vehicle-to-home (V2H) turns an EV into a 60–130 kWh reserve. It needs a bi-directional charger, a compatible vehicle and an islanding device; GM and Ford both sell home-integration bundles [24][36]. Check the vehicle warranty terms and the continuous kW the system can deliver.
04 · System assembler
Build your microgrid, line by line
Pick your loads and equipment. Costs, production, backup runtime and code flags update instantly. The outage simulator further down uses this exact configuration.
Bill of materials
low · typical · high| Item | Spec | Low | Typical | High |
|---|
Estimates use the cited 2026 price ranges, including installation where the source reports installed cost. Lines marked “est.” are planning assumptions. Get at least three local quotes.
Prices and codes move every quarter. Get the update when they do.
Get The Resilience Brief05 · Sizing checklist
Sizing a typical single-family home
Work through these before you call installers. You will get better quotes and catch the expensive surprises early.
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06 · Cost breakdowns
What three common builds cost in 2026
Typical installed cost by component, using the same price model as the assembler. Your build is added as a fourth bar and updates live.
Incentives after the 2025 tax law
Homeowners
The 30% residential clean energy credit (25D) does not apply to expenditures made after December 31, 2025. The IRS treats an expenditure as made when installation is complete [5][6]. Leases and power-purchase agreements can still pass a commercial credit through in the price [2].
Businesses and third-party owners
Solar under the 48E credit that begins construction after July 4, 2026 must be placed in service by December 31, 2027 [7]. Storage keeps full 48E value for projects beginning construction through 2033, then phases down, subject to foreign-entity-of-concern sourcing rules [8].
State and utility programs
Battery rebates, virtual power plant payments and demand-response programs vary widely and can outweigh the lost federal credit. Check your state energy office and utility before signing.
07 · Resilience scenarios
Stress-test it against a real outage
An hour-by-hour simulation of your assembled system. The outage starts at 6 p.m. with a full battery, the worst common case, because the night comes first.
Model: hourly load shapes, a clear-sky solar curve scaled by daily weather factors, 0.8 system derate, 95% usable battery, inverter power limits, generator starts below 25% charge and stops at 80%, EV reserve tapped below 15%. Real systems differ; treat results as directional.
08 · Codes & standards
The listings your inspector will ask about
| Standard | Covers | Why it matters at home |
|---|---|---|
| IEEE 1547-2018 / UL 1741 SB | Interconnection and grid-support functions for inverters | Utilities require it for interconnection; governs anti-islanding and ride-through [33] |
| UL 9540 | Energy storage system safety listing | The system-level listing most jurisdictions require [29] |
| UL 9540A | Thermal-runaway fire propagation test method | Needed for larger units or reduced spacing; residential ESS units are generally capped at 20 kWh without it [30] |
| UL 1973 | Batteries for stationary use | Cell and module safety beneath the system listing [33] |
| NEC Article 690 | Solar PV systems | Wiring, rapid shutdown, disconnects |
| NEC Article 705 (Part II) | Interconnected power sources; microgrid systems | Defines microgrid operation and microgrid interconnect devices [32] |
| NEC Article 706 | Energy storage systems over 1 kWh | 706.15 requires an outdoor emergency shutdown for one- and two-family homes [31] |
| NFPA 855 / IRC R328 | Installation of stationary storage | Location, spacing and aggregate capacity limits; your local fire authority decides |
| UL 3010 (in development) | Microgrid interconnect equipment | Expected to standardize MID testing [32] |
The Resilience Brief
One email a month on keeping the lights on.
Price moves for panels and batteries, code and incentive changes, and teardown-level case studies from real outages. Written for homeowners, small-business operators and the people who advise them.
- Quarterly installed-price tracker for solar, LFP storage and smart panels
- What changed in the NEC, UL listings and federal or state incentives
- After-action reviews of how home systems performed in named storms
Sources
References
Accessed November 2026. Vendor prices change often; confirm before purchase.
- EnergySage, “Home energy market H1 2026 highlights.” energysage.com/news/home-energy-market-h1-2026-highlights
- pv magazine, “Residential solar prices rise 3.2% as third-party ownership gains ground.” pv-magazine.com
- Solar.com, “Solar panel cost” (SEIA/Wood Mackenzie benchmark). solar.com/learn/solar-panel-cost
- SolarReviews, “Solar panel cost.” solarreviews.com/solar-panel-cost
- IRS, “FAQs for modification of sections 25C, 25D … under Public Law 119-21.” irs.gov
- Congressional Research Service, IN12611. congress.gov/crs-product/IN12611
- IRS Notice 2025-42 (beginning of construction). irs.gov/pub/irs-drop/n-25-42.pdf
- RMI, “State online clean energy incentive toolkit: incentives for businesses.” rmi.org
- EnergySage, “Tesla Powerwall review.” energysage.com
- EcoFlow, “How much is a Tesla Powerwall.” ecoflow.com
- Axis Intelligence, “Home battery storage cost.” axis-intelligence.com/home-battery-storage-cost
- RenewEstimator, “Best home batteries 2026.” renewestimator.com
- BloombergNEF, “Lithium-ion battery pack prices fall to $108 per kilowatt-hour.” about.bnef.com
- SurgePV, “Solid-state battery solar storage design.” surgepv.com
- SurgePV, “Future of energy storage.” surgepv.com/hub/energy-storage/future-storage
- OEM Battery Pack, “Solid-state and semi-solid battery applications.” oembatterypack.com
- The Home Depot, Sol-Ark 15K-2P listing. homedepot.com
- Current Connected, EG4 inverters. currentconnected.com/eg4-inverters
- BigBattery, EG4 12kW 18kPV hybrid inverter (GridBOSS option). bigbattery.com
- EnergyBS, “Best smart electrical panel 2026.” energybs.com
- SolarReviews, “Smart electrical panel comparison: SPAN vs. Lumin.” solarreviews.com
- EnergyBS, “Generator transfer switch installation cost 2026.” energybs.com
- Generac, “Backup generator installation.” generac.com
- The Charge Port, “V2H and V2G.” thechargeport.com/v2h-v2g
- Ford, “Bidirectional home power.” fromtheroad.ford.com
- U.S. EIA, “Electricity use in homes.” eia.gov
- U.S. EIA, Electric Power Monthly, Table 5.3. eia.gov
- U.S. EIA, Today in Energy (2024 outage duration). eia.gov/todayinenergy/detail.php?id=66744
- UL Standards & Engagement, UL 9540. shopulstandards.com
- Battery Design, “UL 9540.” batterydesign.net
- Mayfield Renewables, “2023 NEC updates for energy storage systems.” mayfield.energy
- UL Solutions, “Distributed energy resource systems and microgrids: what code authorities should know.” ul.com
- American Clean Power, “ESS codes and standards overview.” cleanpower.org
- The Energy Collective, “Home battery backup.” theenergycollective.com
- How To Store Electricity, “Home solar battery price.” howtostoreelectricity.com
- GM Energy, products. gmenergy.gm.com/products
- FeeGuides, “Generac generator installation cost.” feeguides.com
- The Watt Guide, “Smart electrical panel.” thewattguide.com
- UseCalcPro, “Transfer switch install cost calculator.” usecalcpro.com
- Hyre Electrical, “Power outage hours by state.” hyreelectrical.com