A house backup system, a campervan, a remote cabin, and a portable power pack are built from the same handful of parts — loads, sources, charging and control, storage, conversion, distribution, protection, and monitoring. That shared vocabulary is why it feels safe to copy a wiring diagram or a battery choice from one into another. It usually is not. The parts are the same; the constraints around them are not, and the constraints are what decide whether a design is adequate, legal, and safe.

This pillar gives you a way to pick the right application template before you borrow anything. It compares the major architectures on a consistent set of axes, then hands off to the detailed planning guides and the shared fundamentals rather than repeating them. Use it to choose which questions your project has to answer — not to choose hardware, which no application label can do for you.

One architecture language, different constraints

Every small system can be described with the same functional blocks: the loads it serves, the sources that supply energy, the charging and control that get that energy into storage correctly, the storage itself, the conversion between DC and AC, the distribution and protection that carry power safely, and the monitoring that shows what is happening. If that model is new, start at understanding small energy systems.

What changes between applications is the allowable architecture and the ratings each block must meet. A grid connection, a moving vehicle, an occupied sleeping space, a winter with little sun, or a certification requirement can each rule out a design that would be perfectly fine somewhere else. So the useful question is never "what does a good system look like?" but "what does a good system look like here, under these constraints?"

Homes: grid service, backup, and standalone are not synonyms

Three home architectures get blurred together, and the differences are the whole point:

  • A grid-connected home uses the grid as its main source and, often, as a place to export surplus.
  • A backup / islandable home keeps selected loads running when the grid fails.
  • A standalone property has no grid to lean on at all.

The trap is assuming that having solar panels means having backup. It generally does not. The U.S. Department of Energy is explicit that ordinary grid-tied PV shuts down during an outage for safety, and that powering a home while the grid is down requires an inverter and controls configured for islanded operation, usually paired with storage or another stabilizing source. Grid-tied production and outage backup are separate capabilities; a system can have the first and none of the second. The exact interconnection, anti-islanding, and reconnection rules are set locally and by your equipment — confirm them for your project rather than assuming the general principle covers the specifics.

Backup and standalone: define the service outcome first

Backup and standalone projects go wrong when they start from a battery size. They should start from what must keep working, and for how long.

The national-laboratory way of framing this is a critical load: the load the system is required to meet during a defined outage. Name those services, then attach a duration, the simultaneous and startup power they need, the recharge opportunity you actually have, and the consequence if they fail. Those inputs determine the architecture; the battery is an output, not a starting point. The same discipline drives the shared method in how to design and size a small energy system, which turns a daily energy figure and a power profile into a preliminary size.

Treat "critical load" as named services, not a percentage. A number like "50% of the house" hides whether the half that survives includes the medical device, the sump pump, or the refrigerator holding medicine — which is exactly what a backup plan exists to protect.

Vehicles: movement, mass, and the base vehicle join the design

A conversion is not a stationary system that happens to move. It adds constraints stationary advice never captures.

First, the base vehicle has model-specific electrical interfaces and modification limits. A modern alternator, for example, is not a fixed-voltage source you can freely tap; smart alternators vary or stop their output, and safe charging generally needs a controlled DC-DC charger matched to the exact vehicle. Second, the energy system consumes payload and changes how the vehicle carries weight. Manufacturer upfitter documentation — the Mercedes-Benz Sprinter Body and Equipment Guidelines is one current example — treats payload, permissible axle loads, gross vehicle mass, and centre of gravity as planning inputs, and directs builders to the exact model's figures rather than generic "van" numbers. Batteries are heavy and low; mount them wrong and you have changed the vehicle's handling and its axle loading, not just its wiring.

The detailed method lives in planning a campervan energy system. The point for the matrix: a vehicle project must satisfy the base-vehicle documentation, the equipment manuals, and local vehicle-modification and weight rules — none of which appear in a home design.

Standalone properties: the deficit has nowhere else to go

A cabin, remote workshop, or off-grid home must close its own energy balance in every season it operates, because there is no grid to quietly fill a shortfall. That shifts the weight of the design away from an annual-average yield and toward the worst relevant period: load timing, the poorest sun or resource month you must run through, autonomy, a controllable backup source, fuel and logistics, unattended operation, and how the system recovers after it is drained.

A system sized to average conditions is short every winter. Standalone sizing is therefore built around the month you must survive, not the year you average — the same reason the sizing guide tells you to design generation for a realistic poor month. Which sources are even available to you is a separate question, covered in power sources for small energy systems.

Portable is an equipment category, not permission to improvise

A portable power station is a genuinely useful, self-contained product — and it is not automatically equivalent to an installed backup or distribution system. Its permitted loads, operating environment, charging inputs, ventilation and clearance, expansion, and above all any connection to a building's wiring must follow its manual and local rules.

UL Solutions makes the sharp version of this point: a cord-and-plug portable pack wired into panel or switch arrangements may not carry the certification a stationary residential energy-storage system requires. "Portable" describes the box; it does not license an improvised installation. If a portable product is going to feed premises wiring, that interface is governed exactly as a fixed system's would be.

Marine: stop and change rulebooks

Boats look like the closest cousin to a campervan, and that resemblance is a trap. Marine electrical systems are a specialised boundary with their own standards. The current ISO small-craft scope (ISO 13297:2020, with Amendment 1:2022) explicitly covers combined AC and DC installation requirements on small craft, and a revision is in progress — so the applicable edition, amendment, and local adoption must be confirmed for the specific project. Do not carry van guidance onto a boat; change rulebooks and get competent marine help.

The application-selection matrix

Compare your project on stable axes, then follow the row that fits. Every cell below is a decision to resolve locally, not a value to copy:

Application Normal source When the grid/source is gone Dominant added constraint Governing regime to confirm
Grid-connected home Grid (+ optional PV export) No power unless islanding-capable Interconnection & export rules Utility + electrical/building code
Home backup Grid, with islanded mode Runs named critical loads for a set outage Safe transfer & isolation Utility, electrical, fire, ESS listing
Campervan / RV Solar, controlled alternator, shore Runs on stored energy; recharge is opportunistic Motion, mass, occupied space Vehicle modification, weights, shore/AC rules
Standalone cabin Own generation + storage Must self-supply every season Worst-month balance & recovery Electrical/building; land use
Workshop Grid or standalone Depends on architecture chosen Large startup/surge loads Electrical code for the loads
Portable system Self-contained + charge inputs Runs to its rated capacity Per-product limits; no improvised wiring Product manual + local rules if tied to premises
Marine (boundary) Solar, engine, shore Runs on stored energy Marine electrical environment ISO small-craft + local marine rules

Read down the axes that matter to your project. Two applications that share a "normal source" can still demand completely different transfer, mounting, and certification work — which is why the matrix compares constraints, not products.

Use the matrix to choose questions, not hardware

The application label does not pick your battery chemistry, system voltage, inverter size, protection scheme, or maintenance plan. Those follow from the project's loads, environment, source opportunities, service model, exact equipment, and governing requirements — the actual design work. Marketing tends to group portable packs, home backup, RV kits, and off-grid systems by battery size; regroup them by architecture, interfaces, environment, and rulebook instead.

Where an interface is undefined — grid, shore, generator, vehicle, or premises wiring — or where equipment would be used outside its documented application, that is a stop condition, not a detail to improvise. Grid and premises connections, vehicle electrical and structural integration, any marine project, and protection, grounding, bonding, and isolation design are places to bring in the relevant authority and a qualified professional. See the safety fundamentals for the general hazard model before you commit to any architecture.

Key takeaways

  • Every application shares the same functional blocks, but the allowable architecture and ratings depend on application-specific constraints.
  • Solar does not equal backup: grid-tied PV generally shuts down in an outage; islanded operation needs the right inverter, controls, and usually storage.
  • Backup and standalone projects start from named critical services and an outage scenario, not from a battery size.
  • Vehicles add the base vehicle, mass, axle loading, and motion; portable products add per-product limits; marine changes the rulebook entirely.
  • The matrix chooses which questions your project must answer — it cannot choose hardware, and it is not an installation design.

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