Residential Microgrid Glossary

An operating state in which an appropriately configured property electrical system is isolated from the utility grid and supplied by local resources such as storage or generation. Island-mode capability, transition behavior, supported loads, and runtime depend on system architecture, approved protective equipment, available energy, and site conditions.

The total amount of energy a battery system can store, measured in kilowatt-hours (kWh). A home drawing 10 kW continuously would deplete a 13.5 kWh battery in approximately 81 minutes. Whole-home microgrid systems for large estates typically require 40–200+ kWh of storage to provide meaningful outage duration before generator activation.

The maximum rate at which a battery system can deliver power continuously, measured in kilowatts (kW). Distinct from storage capacity (kWh) — a battery can have large storage but limited output. A 5,000+ sq ft home in operation may draw 15–30 kW simultaneously. Consumer batteries (Powerwall 3: 11.5 kW) may not support the full load of a large estate.

The intelligence layer of a residential microgrid — a dedicated power management computer that monitors all energy sources and loads in real-time, optimizes battery state of charge, decides when to start/stop generators, manages power flow between sources, executes load shedding if needed, and enables remote monitoring. A microgrid controller is what distinguishes a true microgrid from a collection of independently operating devices. Consumer battery products use basic inverter logic, not a dedicated controller.

The current energy level of a battery bank expressed as a percentage of total capacity. Example: a 40 kWh battery at 75% SOC holds 30 kWh of usable energy. Microgrid controllers continuously monitor SOC and use it to make operational decisions — when to charge from solar, when to start the generator, and what minimum SOC floor to maintain for emergency reserve.

The pattern of electricity consumption across a property over time — how much power is drawn by which loads, at which times of day and year. Load profiling is the foundation of microgrid design: battery sizing, generator sizing, and solar sizing all derive from the actual load profile of the specific property. Generic 'average home' sizing is inadequate for large estates with HVAC, EV charging, pools, and other high-draw systems.

A sub-panel containing only essential circuits — typically refrigerator, some lighting, phone charging, and select outlets. Consumer battery backup products (Powerwall, PWRcell, Enphase IQ) typically only back up a critical load panel, not the full main panel. This means HVAC, water heaters, EV chargers, pools, and other high-draw systems lose power during an outage even with a consumer battery installed. A whole-home microgrid backs up the main panel — every circuit.

The intentional, controlled reduction of electrical consumption to match available generation capacity. Executed automatically by a microgrid controller during low-generation periods (cloudy days, low fuel) or high-demand spikes. Load shedding prioritizes critical loads and temporarily suspends lower-priority loads (pool heaters, EV charging) to maintain system stability. Prevents battery depletion during extended outages.

A utility billing arrangement in which excess solar generation exported to the grid is credited against the property's utility bill. Availability and credit rates vary significantly by utility and state. Florida, Texas, and California have different net metering structures. Microgrid-connected solar systems can participate in net metering when grid-tied, subject to utility interconnection agreement terms.

A formal agreement with the local utility required before connecting any on-site generation system (solar, generator, battery) to the grid. Sets technical requirements for the connection, establishes metering terms, and may include net metering provisions. Required for all grid-tied microgrid installations. Processing time varies from 2–12 weeks depending on utility and jurisdiction. Prime Microgrid manages the full interconnection process.

Electric Reliability Council of Texas. Operates the Texas electrical grid as an island largely isolated from the U.S. Eastern and Western Interconnections — Texas cannot easily import emergency power from neighboring states. ERCOT's isolation, combined with extreme weather events (Winter Storm Uri, summer heat waves) and population growth outpacing generation capacity, makes Texas one of the highest-risk grid environments in the country for residential power continuity.

Two common lithium battery chemistries used in residential storage. Lithium Iron Phosphate (LFP) prioritizes safety, long cycle life (3,000–6,000+ cycles), and thermal stability — better for whole-home applications where longevity and safety are paramount. Nickel Manganese Cobalt (NMC) offers higher energy density (more kWh in less space) but with higher thermal sensitivity. Residential microgrids designed for multi-decade operation typically favor LFP chemistry.

Solar panels that convert sunlight directly into DC electricity. In a microgrid, solar PV is one generation source managed by the microgrid controller — typically the primary source during daylight, charging batteries and supplying loads directly. Solar can be grid-tied (exporting excess), battery-coupled (charging storage), or both. Solar output is variable by weather and season; microgrid design accounts for seasonal variation, particularly in northern latitudes.

Two common fuel options for residential backup generators. Natural gas is convenient (no on-site storage, runs from utility supply) but is vulnerable to supply disruption during major outages — a critical failure point exposed during Winter Storm Uri when natural gas infrastructure failed across Texas. Propane requires on-site tank storage but provides fuel independence from utility infrastructure. Remote properties and storm-resilient systems often use propane for this reason.

An engineering drawing that shows the electrical configuration of a system — how components (utility connection, solar, batteries, inverters, generator, transfer switches, panels) are connected. The SLD is the primary engineering document for a microgrid installation, required for permitting and utility interconnection. It is the first deliverable from a proper microgrid engineering engagement. A contractor who cannot produce an SLD is not doing engineering.

A locally controlled energy system that integrates distributed generation, energy storage, and loads — and can operate both connected to the main utility grid and independently (islanded). A residential microgrid is the application of this architecture to a private property. The defining characteristic of a microgrid is intelligent, coordinated control: components don't just coexist, they are actively managed as a unified system. This is what distinguishes a true microgrid from a generator + battery installed at the same address.

A power electronics device that converts DC (direct current) electricity — from solar panels or batteries — to AC (alternating current) electricity that home circuits use. In a microgrid, inverters are bidirectional: they can also convert AC grid power to DC to charge batteries (operating as a rectifier). Inverter capacity sets the maximum AC output a battery system can deliver. A 10 kW inverter can sustain 10 kW of continuous AC output regardless of how large the battery bank is. Inverter selection is a critical engineering decision — residential microgrids typically use multi-mode inverters capable of grid-tied and off-grid operation simultaneously.

The act of a power system continuing to operate and supply power to a local area after the surrounding utility grid has disconnected. In residential microgrids, intentional islanding is the core resilience feature — when the utility grid fails, the system islands automatically and continues powering the property. Anti-islanding is a safety requirement in grid-tied systems: inverters must detect grid failure and disconnect from the utility to prevent backfeeding live power onto de-energized utility lines, protecting utility workers. Microgrid-grade systems handle both: safe disconnection from the grid and immediate transition to island operation.

Small-scale power generation, storage, and demand-response assets located at or near the point of consumption — as opposed to centralized utility generation plants. Examples include rooftop solar, residential battery storage, EV chargers (acting as loads or future V2G sources), and small generators. A residential microgrid integrates multiple DERs under one control architecture. Utilities are increasingly interested in aggregating residential DERs for grid services, but the primary value for estate owners is local resilience — not grid participation.

The engineering process of ranking a property's electrical loads by criticality, and configuring the microgrid controller to sustain high-priority loads first when system capacity is constrained. Typical priority tiers: Tier 1 (life-safety) — security systems, medical equipment, communications; Tier 2 (comfort/protection) — HVAC, refrigeration, lighting; Tier 3 (convenience) — EV charging, pool heaters, decorative lighting. During extended low-generation periods, the controller automatically curtails Tier 3 loads before Tier 2, and Tier 2 before Tier 1. Load prioritization is programmed during system commissioning, not a factory default.

A power system that combines multiple generation or storage technologies operating as one integrated unit. In residential applications, the most common hybrid configuration is solar + battery + generator: solar generates during daylight, batteries provide instant-on backup and buffer storage, and the generator activates automatically to recharge batteries or sustain loads during extended outages. The term 'hybrid' is sometimes used loosely — the distinguishing factor is whether the components are truly coordinated by a controller or merely co-located. A true hybrid system has unified management; a generator and a battery installed by different contractors are not a hybrid system.

The maximum rate of electricity consumption at a property during a given period, measured in kilowatts (kW). Peak demand drives system sizing: inverters, batteries, and generators must all be capable of sustaining the peak load without voltage sag or system trip. A large home may have a 10 kW average draw but a 35 kW peak when HVAC compressors, EV chargers, and kitchen appliances all operate simultaneously. Microgrid systems are sized for the peak, not the average — a common engineering failure in underpowered systems. Utilities also charge large commercial customers a separate peak demand fee; residential microgrids with energy management can minimize this charge.

On-site electrochemical energy storage that allows a property to store electricity and discharge it on demand. In a microgrid, storage may support backup operation, energy buffering, and reduced generator runtime. Transfer behavior depends on the selected equipment, system design, and operating conditions. Storage is sized in kWh for energy capacity and kW for power output; both metrics affect supported loads and duration.

The percentage of energy retained after storing and retrieving it from a battery system. If 100 kWh is put into a battery and 85 kWh is recoverable, round-trip efficiency is 85%. LFP batteries typically achieve 94–98% round-trip efficiency. Round-trip efficiency affects solar self-consumption economics and overall system performance. Lower efficiency means more generation is required to deliver the same usable energy — relevant when sizing solar arrays for battery-coupled systems.

The percentage of a battery's total capacity that is used in a single discharge cycle. Most lithium battery systems are rated at 80–90% DoD — meaning a 100 kWh battery delivers 80–90 kWh of usable energy per cycle. Repeatedly discharging below the recommended DoD accelerates battery degradation. Microgrid controllers enforce DoD limits automatically, maintaining a minimum state of charge floor for emergency reserve and battery longevity.

A function in which a backup generator starts automatically — without human intervention — when triggered by a microgrid controller signal. Triggers include: battery state of charge falling below a threshold, sustained high load demand, or extended outage duration. Auto-start is standard in properly integrated microgrid systems and is what enables true unattended operation. A generator with manual-start only requires someone on-site to activate it — a critical limitation if owners have evacuated or are traveling.

A measure of how efficiently electrical power is being used, expressed as a ratio between 0 and 1 (or 0–100%). A power factor of 1.0 (unity) means all supplied power is consumed as useful work. Inductive loads — motors, compressors, HVAC units — draw reactive power and reduce power factor below 1.0. For microgrid sizing, real (useful) power in kW and apparent power in kVA must both be considered. An inverter or generator rated at 10 kVA may only deliver 8 kW at 0.8 power factor. Estate-scale microgrids account for power factor in both generation and storage sizing.

Two architectures for connecting solar, batteries, and inverters. In a DC-coupled system, solar panels and batteries share a common DC bus — solar charges batteries directly before inversion to AC. In an AC-coupled system, solar has its own inverter producing AC power, which is then re-converted to DC to charge batteries — introducing conversion losses. DC-coupled systems are typically more efficient (one conversion stage). AC-coupled systems are easier to retrofit onto existing solar installations because the existing solar inverter is preserved. Microgrid retrofits on properties with existing solar are often AC-coupled for this reason.

An electricity pricing structure in which the cost per kWh varies by time of day and season. Peak rate periods (typically late afternoon/evening) are significantly more expensive than off-peak periods (overnight). A battery-equipped microgrid can be programmed for arbitrage: charge batteries during cheap off-peak hours and discharge during expensive peak periods, reducing the utility bill without changing consumption behavior. TOU optimization is increasingly relevant in high-rate states like California ($0.35–$0.55/kWh peak) and Connecticut ($0.28–$0.40/kWh).

The duration between utility-grid failure and backup-power activation at a property's electrical panel. Transfer time and its effect on connected loads depend on the selected transfer equipment, inverter or generator platform, system design, configuration, and operating conditions. Product specifications and commissioned test results should be reviewed for each project.

The ability to expand a power system's capacity by adding additional modules — battery strings, solar arrays, or generation units — without replacing the existing architecture. LFP battery systems are generally modular; new battery cabinets can be added to expand kWh capacity. Inverter and controller platforms must support the expanded capacity. Scalability is relevant for estate owners whose electrical loads grow over time (EV chargers added, home additions, new pool equipment). A properly specified microgrid architecture accounts for planned future expansion.

Two installation configurations for solar PV arrays. Rooftop mounting uses existing structure but is constrained by roof area, orientation, shading, and structural load limits — and complicates roof access for maintenance or replacement. Ground-mounted systems are unconstrained by roof geometry, can be optimally oriented, and are easier to maintain and expand. For large residential estates with sufficient land, ground-mounted solar arrays are often preferable. Coastal properties may also benefit from ground mounting at flood-rated elevations.

An electrochemical device that generates electricity from hydrogen or natural gas through a chemical reaction rather than combustion. Relevant in the residential microgrid space as an alternative or supplement to conventional generators — fuel cells run silently, with higher efficiency than combustion generators, and emit primarily water vapor when hydrogen-fueled. Commercial adoption in residential applications is growing but remains limited by hydrogen supply infrastructure and equipment cost. Current residential microgrids primarily use gas or propane generators; fuel cells are a technology to watch for future system architectures.

An engineering reliability standard in which a system includes at least one more component than the minimum required for operation. If N components are needed, N+1 are installed — so that any single component failure does not cause a system outage. In residential microgrid terms: two battery strings where one would suffice, or a backup generator in addition to solar and batteries. N+1 is standard in mission-critical infrastructure (data centers, hospitals) and is the appropriate standard for high-value estate properties where power continuity is non-negotiable.

A residential microgrid is an integrated electrical system for a home or residential property that coordinates onsite generation, battery energy storage, backup power, intelligent controls, property loads, and utility-grid interaction. Depending on its design, it may operate in island mode under defined conditions.

A home microgrid is a residential-scale private power system that coordinates local energy resources, electrical loads, controls, protective equipment, and interaction with the utility grid. Solar or battery equipment may be components, but neither alone necessarily constitutes a complete microgrid.

A solar battery system combines solar panels with battery storage so energy generated during sunlight hours can be stored and used later.

A backup generator produces electricity during outages or backup conditions. In a microgrid, it may work with batteries, transfer equipment, and load controls.

Generator integration is the process of connecting a generator into a broader home energy system so it can operate safely and effectively with other equipment.

Critical loads are the electrical circuits or devices a homeowner wants to keep powered during an outage.

Load management is the process of controlling which circuits receive power during backup conditions to avoid overload and preserve available energy.

Whole-home backup refers to a system designed to power most or all of a home during an outage, depending on available capacity and load management.

Energy resilience is the ability of a home or property to maintain essential power during disruptions, outages, or grid instability.

Energy independence refers to reducing reliance on the utility grid by using on-site energy resources such as solar, batteries, and generators.

A grid outage occurs when utility power is unavailable due to equipment failure, weather, maintenance, or grid instability.

Solar production is the electricity generated by solar panels from sunlight.

Battery capacity refers to the amount of energy a battery can store, typically measured in kilowatt-hours.

Generator runtime refers to how long a generator can operate based on fuel supply, load, and equipment design.

Intelligent controls monitor and manage energy resources, loads, batteries, generators, and operating modes within a microgrid.

An estate energy system is a customized energy system designed for larger residential properties, high-value homes, or private estates with greater resilience, privacy, and load requirements.

Property-controlled electrical infrastructure designed to coordinate generation, storage, backup resources, controls, protection, loads, and utility-grid interaction according to the owner's operating and resilience requirements.

Equipment that stores electrical energy for later use and includes batteries, power-conversion equipment, controls, protection, and related balance-of-system components. It may be part of a microgrid but is not a complete microgrid by itself.

Electricity generation located at the property, which may include solar or compatible generator resources. In a microgrid, onsite generation is coordinated with storage, loads, controls, and the utility interface.

Electrical power supplied by local equipment when normal utility service is unavailable or unsuitable. Coverage, transfer behavior, and runtime depend on the equipment and system design.

The public electricity network that delivers power to a property. A grid-connected microgrid may exchange power with this network while using protective and control equipment to manage the interface.