What Size Standby Generator Does Your Home Need?

The right answer to whole house generator sizing is not a number based on square footage, the main breaker’s ampere rating, or an online appliance list. It is a documented operating plan for the actual home. That plan identifies which loads matter during an outage, which can operate together, which motors must start, which loads can be delayed or shed, how fuel reaches the generator, and what test will prove the finished system performs as designed.

A larger nameplate is not automatically a better design. It can change fuel requirements, site options, transfer equipment, controls, and project scope. A smaller unit with vague load-management promises is not automatically efficient or economical either. The defensible size is the capacity of an exact generator, on the proposed fuel and site, that can serve the agreed operating states and starting events through an approved transfer and control configuration.

Generator sizing at a glance

Use this table to organize the decision before accepting a kW recommendation.

Sizing question	Evidence to collect	Decision it controls	Shortcut to reject
What must remain available?	Ranked circuits, equipment, household needs, and acceptable interruptions	Selected-load or broader transfer boundary	“Back up the whole house” without a load schedule
What may operate together?	Credible daytime, overnight, heating, cooling, and water-use scenarios	Required running capacity	Adding every nameplate or using average monthly energy
What must start while other loads run?	Exact motor/compressor nameplates, manuals, locked-rotor or manufacturer starting data	Starting response and control sequence	One generic starting multiplier for every motor
Which loads can wait?	Written priority, delay, shed, and restore rules	Load-management equipment and usable operating plan	“Smart controls handle it” without documented logic
Can the fuel system support the unit?	Proposed-fuel rating, pressure/flow or storage/regulator/piping study	Feasible generator and fuel design	Assuming an existing meter, pipe, or tank is adequate
What does the transfer equipment connect?	One-line diagram, exact switch, selected circuits, service boundary	Connected-load exposure and isolation design	Treating switch amperage as generator capacity
How will performance be accepted?	Staged-load and starting-event test plan with recorded results	Proof that sizing and controls work together	A no-load engine start or exercise cycle alone

The table also explains why two responsible proposals may recommend different equipment. One may preserve central cooling, well pumping, cooking, and water heating together. Another may serve the same priorities by sequencing them. A third may put only essential circuits on backup. The recommendations cannot be compared until their operating promises match.

What a generator’s kW rating does—and does not—tell you

Kilowatts describe real-power capability under stated conditions. They do not, by themselves, describe the complete behavior of a standby system. The proposal should identify the exact model, voltage, phase, frequency, fuel configuration, continuous or standby rating used, environmental assumptions, and relevant starting-performance data. A brochure headline without those qualifiers is not a sizing record.

Residential loads also differ in how they use power. Resistance heat can create a large, relatively steady demand. Electronics may have power-quality requirements. An air-conditioning compressor, heat pump, well pump, sump pump, refrigerator, or other motor can require a short starting event that is materially different from its running demand. The generator and controls must support both the stable operating state and the transitions between states.

Three familiar home numbers are weak sizing substitutes:

• Square footage does not reveal the fuel used for heat and hot water, number or type of HVAC systems, well versus public water, pool equipment, cooking equipment, EV charging, or the household’s outage priorities.
• Main-service amperage is a limit or equipment rating within the utility-service design, not proof that the home normally draws that amount or that a generator should reproduce it.
• Monthly kilowatt-hours measure energy over time. They can hide brief peaks and motor starts, and they do not say which loads created the energy use or whether those loads must operate during an outage.

Interval-meter data can improve the record by showing demand patterns at the meter. It still may not resolve a short motor start, identify the responsible equipment, show a future load, or model an outage-only control sequence. Use it as one input, not an automatic answer.

Start with outage priorities, not an appliance calculator

Before calculating capacity, write down what the household needs the backup system to accomplish. “Everything” is not precise enough. A useful priority inventory links each load to a reason, acceptable interruption, and operating condition.

Consider these categories:

1. Safety and health priorities. Medical equipment, refrigeration for medication, mobility equipment, smoke and carbon-monoxide alarms, communications, security, and lighting may have different tolerance for interruption. A generator is not automatically a medically reliable power system; critical needs may require separate continuity, monitoring, or emergency planning.
2. Water and sanitation. A well pump, septic equipment, sump pump, sewage ejector, or water-treatment system can turn an electrical outage into a water problem. Record the exact motor and how frequently it must operate.
3. Temperature and humidity. Identify the exact HVAC zones or equipment required, not simply “air conditioning.” The plan may preserve one system, sequence multiple systems, or use another defined strategy.
4. Food and daily living. Refrigeration, selected receptacles, lighting, internet, garage access, cooking, and water heating should be named. Fuel-burning appliances can still require electrical controls, fans, pumps, or ignition.
5. Property protection. Freeze protection, dehumidification, drainage, gates, alarms, and other unattended functions may matter when the owner is away.
6. Deferrable loads. EV charging, clothes drying, pool heating, resistance backup heat, spa equipment, and other large loads may be acceptable to shed, limit, or operate only under stated conditions. The correct treatment depends on the household, not a universal list.

For each item, classify it as must remain available, may cycle, may be delayed, may be manually enabled, or not backed up. Then state whether its loss for several minutes, several hours, or the full outage would be acceptable. This turns an emotional “whole house” request into an engineering and operational brief.

If the household has not yet decided whether permanent automatic standby is the right operating model, begin with the standby-versus-portable generator comparison. Sizing should follow that choice because connection, automation, operator involvement, and supported loads differ.

Build an equipment record from the actual home

The next step is field evidence. Equipment labels, manufacturer manuals, electrical records, and observation are more useful than generic web wattage tables. Record at least:

• equipment description and location;
• supply voltage and phase;
• circuit and protective-device information;
• nameplate input, current, power, or other relevant rating;
• motor or compressor starting information where available;
• whether the load is fixed, variable, staged, or controlled;
• fuel source for equipment that uses both fuel and electricity;
• normal operating mode and unusual modes such as defrost, auxiliary heat, regeneration, or charging;
• proposed outage priority; and
• manual or automatic control that changes its operation.

Do not assume a breaker rating equals the load. A breaker protects a circuit under its design rules; it is not a measurement of ordinary demand. Do not assume the product’s marketing output equals its electrical input. Do not copy a similar neighbor’s equipment. Model and configuration matter.

The field review should also document the service, panels, transfer location, available circuit records, solar, batteries, EV equipment, surge protection, wells, pools, detached structures, and any existing generator or inlet. This does not mean every item belongs on backup. It prevents an overlooked interconnection or control conflict from appearing after equipment is selected.

Model credible simultaneous operating states

A running-load calculation should describe what can reasonably operate at the same time during an outage. It should not blindly add every nameplate, but it also should not discard inconvenient loads without an enforceable control or operating rule.

Build several scenarios rather than one total. For example:

• Cooling-day occupied state: the selected cooling equipment, refrigerator, well or water equipment, communications, lighting, and ordinary receptacle allowance.
• Overnight state: refrigeration, water or drainage equipment, selected HVAC, security, communications, and bedroom loads.
• Cold-weather state: heating equipment, pumps or blowers, any approved auxiliary-heat treatment, water systems, and essential household loads.
• Unoccupied state: property protection, refrigeration, security, communications, drainage, and temperature/humidity control expected while nobody is present.
• Recovery state: loads likely to request operation shortly after transfer, including thermostats, pumps, refrigerators, chargers, and controls that see power return together.

The recovery state is easy to miss. When utility power fails and the standby source becomes available, several devices may call at nearly the same time. A design can use intentional delays or priorities, but those controls must be real, compatible, and tested. A homeowner’s intention to “remember not to run everything” is not an automatic control plan for an unattended system.

The assessment should identify diversity assumptions explicitly. If two large loads are assumed not to overlap, state what prevents the overlap. If the answer is a controller, name its function and failure response. If the answer is owner behavior, decide whether that is acceptable when the home is empty or another person is present.

Motor and compressor starting can control the answer

Many motors draw a short starting current above their normal running current. The generator must keep voltage and frequency behavior within the limits required by the exact equipment and system while other priority loads are operating. A generator that carries the stable running total may still struggle with the transition when a large compressor or pump starts.

Collect exact starting information for likely controlling loads, which may include:

• central air-conditioning or heat-pump compressors;
• well, sump, sewage, irrigation, or pool pumps;
• refrigeration compressors;
• workshop, lift, gate, or air-compressor motors; and
• equipment with electric auxiliary heat or staged elements.

Do not apply one generic multiplier to every motor. Starting behavior changes with motor design, controls, variable-speed drives, soft-start equipment, voltage, mechanical load, and the generator’s response. A label may provide locked-rotor amps or other data, but the qualified designer must interpret the exact equipment documentation and proposed configuration.

Sequence matters too. The controlling case may be a well pump starting while the selected HVAC system and refrigerator already run. It may be HVAC recovery immediately after transfer. It may be an auxiliary-heat stage that should be blocked on generator power. The record should name the event, the background loads, the intended control response, and the acceptance criterion.

Adding a starting aid or control is not a generic cure. The exact accessory must be compatible with the connected equipment, installed as approved, reflected in warranty and service records, and verified during commissioning. This page does not assume every motor can or should be modified.

Separate transfer boundary from generator capacity

A transfer switch safely changes the connected electrical system from the normal source to the alternate source in its approved configuration. Its ampere rating describes the switch; it does not prove the generator can carry every load downstream.

The proposal should identify one of these operating boundaries or another clearly documented design:

• Selected-load design: only identified circuits or a dedicated backed-up panel transfer to the generator.
• Whole-service transfer with load control: a broad service boundary transfers, while defined loads are shed, delayed, sequenced, or limited so generator demand stays within the approved operating plan.
• Whole-service transfer without active shedding: the design relies on a documented calculation, operating assumptions, equipment capability, and any manual restrictions. The phrase does not itself mean every connected load can run simultaneously.

Ask for a one-line diagram and an exact circuit/load schedule. It should show the transfer equipment, service/disconnect relationship, panels, generator, control devices, and important connected loads. UL Solutions explains that UL 1008 covers applicable automatic and nonautomatic transfer switches. The listing and approved configuration matter, but neither replaces a load study.

The transfer design also needs a defined automatic sequence: utility-loss recognition, generator start, source availability, transfer, load restoration, utility return, retransfer, and cooldown or shutdown behavior as applicable to the exact system. Manufacturer settings and AHJ requirements control the project; generic internet timing values should not be written into a contract.

Load shedding is an operating strategy, not extra capacity

Load management can make a narrower generator design practical when the household accepts a defined priority plan. It does not create power. It controls when selected loads may operate so the active demand and starting events remain within the system’s limits.

A useful load-control schedule answers:

1. Which loads are permitted immediately after transfer?
2. Which loads are delayed, and what condition ends the delay?
3. Which loads are shed when demand or another priority load calls?
4. In what order are loads restored?
5. Is the system measuring generator load, service load, voltage, frequency, a control signal, or another input?
6. What happens after communication, sensor, contactor, relay, or controller failure?
7. Can the homeowner enable or disable a load manually, and under what restrictions?
8. What indication or alert shows that a load has been shed or a control has failed?
9. How will every priority stage be demonstrated at acceptance?
10. Who updates the schedule after HVAC, EV, pool, water-heating, or panel changes?

A verbal statement such as “the air conditioners take turns” is incomplete. The homeowner needs to know which one has priority, whether water equipment can interrupt cooling, how long a load may remain unavailable, and what happens when several devices call together. Likewise, a controller marketed as smart or whole-home does not establish its approved function, compatibility, or fail-safe behavior.

Load management can improve the match between equipment and actual priorities. It can also create an experience the homeowner dislikes if the proposal never explains tradeoffs. A smaller managed design may be appropriate when deferrable loads are clearly identified and short interruptions are acceptable. A selected-load design may be clearer where predictable essentials matter more than access to every circuit. A broader design may be justified when simultaneous operation is genuinely required and the electrical, fuel, site, and budget scope can support it. None is universally best.

Fuel deliverability is part of sizing

A generator’s electrical output depends on an engine receiving fuel within the exact manufacturer’s requirements. Selecting a nominal kW and postponing the fuel review can produce a design that is not deliverable at the property.

Natural-gas review

The qualified fuel-system review should address the exact generator demand, required inlet pressure range, meter and regulator capability, existing connected gas loads, pipe material and route, equivalent length and fittings, utility or provider requirements, and pressure under the relevant operating condition. Existing furnaces, water heaters, cooking equipment, fireplaces, pool heat, and other gas loads may matter.

An existing gas meter or nearby pipe does not prove sufficient capacity. A utility account does not promise gas availability during every outage. The proposal should identify who requests any provider review or meter/regulator work, what is included, and what happens if the preferred generator cannot be supported.

Propane review

A propane design should address the generator’s exact fuel requirement, tank and regulator arrangement, usable storage under applicable conditions, vaporization capability, outdoor temperature, other connected appliances, piping, tank location, access, anchorage or flood considerations, inspections, and the owner’s refill plan. The party responsible for tank, regulator, piping, startup supply, and ongoing delivery should be named.

Tank water capacity is not the same as usable fuel in all conditions, and a fuel-consumption table is not a runtime guarantee. Actual load varies; environmental conditions, storage, regulator/piping performance, maintenance, and delivery access matter. This article therefore does not publish a universal tank size, operating duration, or refill interval.

South Carolina maintains a separate LP-gas licensing and permit path for covered work. The proposal should identify the qualified party for each fuel scope rather than assuming the electrical contractor, equipment dealer, gas utility, or propane supplier owns all of it.

Verify the rating for the exact fuel, model, and site

The same generator family may have different published capability depending on fuel and configuration. Site conditions and required accessories can also affect the selected equipment or installation. Use the current technical data and installation manual for the exact model—not a dealer summary for a related unit.

Request a sizing record that identifies:

• exact generator model and proposed fuel;
• electrical rating used in the calculation;
• voltage, phase, and frequency;
• ambient-temperature, elevation, ventilation, or other environmental assumptions addressed by the manufacturer;
• starting-performance data used for the controlling event;
• required cold-weather, coastal, corrosion, or other site accessories where supported by the exact documentation;
• breaker and transfer/control configuration; and
• revision dates for the data sheets and manuals.

Do not apply a generic elevation or temperature derating percentage copied from another model. Do not assume a natural-gas and propane rating are identical. Do not substitute an enclosure label or sales-family name for an exact model number.

Site feasibility remains separate from electrical capacity. Exhaust, building openings, property constraints, flood exposure, drainage, access, noise, maintenance clearance, anchorage, and fuel equipment can affect which unit and location are approvable. FEMA’s flood-resilience guidance shows why the generator, transfer equipment, controls, wiring, fuel storage, anchorage, and access may need to be evaluated together. The current AHJ and property-specific design determine the actual requirements.

Include future loads only when the plan is credible

A standby system can remain at a home through future equipment changes, so it is reasonable to discuss foreseeable loads. It is not useful to oversize around every hypothetical purchase.

List changes with a likely timing and operating expectation:

• replacement HVAC capacity or fuel change;
• heat-pump water heating or electric resistance equipment;
• an EV and whether charging during an outage is actually required;
• a second refrigerator or freezer;
• well, pump, pool, spa, workshop, or detached-building changes;
• solar or battery equipment and the approved interaction, if any;
• an addition, accessory dwelling unit, or occupancy change; and
• a health, mobility, or work-from-home need that changes continuity priorities.

Then choose how each change affects today’s design. The project might reserve physical space, choose expandable controls, document an excluded future load, or include a supported capacity allowance. Future readiness should be written, not implied. An unused breaker position, spare conduit, or higher switch rating does not establish future generator capacity.

After installation, treat a major equipment change as a reason to review the sizing record and control schedule. An HVAC contractor, EV installer, or pool contractor may not know the standby operating assumptions unless the homeowner preserves and shares them.

Apply current South Carolina and local requirements

South Carolina’s Building Codes Council publishes the current adopted-code path and state modifications. The filing-date requirements, local administration, exact property, utility/service arrangement, equipment listing, and manufacturer instructions must be checked for the project. A later model-code article found online is not automatically the rule in effect.

Generator work can cross several scopes: electrical service and transfer, fuel gas or propane, equipment placement, pad or stand, trenching, drainage, flood protection, zoning, architectural review, utility coordination, and inspections. The City of Charleston’s residential generator guidance is one example of those separate review questions. It is not a statewide checklist and should not be applied to another jurisdiction without verification.

Ask the proposal to identify:

• the actual authority or authorities having jurisdiction;
• the code basis and equipment instructions used;
• the qualified entity responsible for electrical design and work;
• the responsible natural-gas utility/contractor or propane licensee, as applicable;
• who prepares plans and calculations;
• who submits permits, responds to corrections, and schedules inspections;
• who coordinates service interruption or utility work;
• unresolved zoning, flood, HOA, or architectural questions; and
• conditions that could require a design change.

This page does not provide DIY electrical, fuel, transfer, or load-testing instructions. Those tasks can create shock, fire, fuel, exhaust, carbon-monoxide, and utility-worker hazards and belong to the approved design and qualified parties.

Turn the sizing study into a same-scope quote record

Before comparing project prices, make bidders show what their recommended size is expected to do. A useful sizing attachment includes:

• ranked outage priorities and excluded loads;
• equipment inventory and source records;
• simultaneous operating scenarios;
• controlling motor-start event and background loads;
• exact generator model, rating, fuel, and assumptions;
• transfer boundary and one-line diagram;
• load-control hardware and written priority sequence;
• fuel-system design responsibility and unresolved provider work;
• site and environmental assumptions;
• future-load treatment;
• commissioning steps and acceptance criteria; and
• design limitations explained to the owner.

If two proposals use different generator sizes, compare the records line by line. Is one excluding electric auxiliary heat? Is one sequencing HVAC and well pumping? Does one assume a gas-system change? Does one use a selected-load panel while the other transfers the service? Is a future EV load excluded, blocked, limited, or fully included? A kW difference becomes understandable when the operating promises are visible.

Once the design basis is consistent, use the generator installation cost guide to normalize transfer equipment, electrical and fuel work, site preparation, approvals, delivery, commissioning, service, and exclusions. Price comparison before sizing normalization rewards ambiguity.

Commission the operating plan, not only the engine

An engine start confirms that the engine started at that moment. It does not prove the transfer sequence, supported operating states, starting response, load controls, fuel delivery, alarms, or owner expectations.

The written acceptance plan should be safe, manufacturer-supported, and performed by the responsible qualified parties. Depending on the approved design, it may document:

1. equipment, firmware/configuration, and control settings;
2. normal-source loss detection and generator start;
3. source availability and automatic transfer;
4. staged application of priority loads;
5. the agreed controlling motor or compressor starts with stated background load;
6. load-shedding, delay, sequencing, and restoration for each controlled load;
7. voltage, frequency, current, fuel pressure, alarms, or other specified observations under load;
8. failure or unavailable-load indications that can be tested safely;
9. utility return, retransfer, and shutdown sequence;
10. monitoring/account behavior if included;
11. owner training, manual controls, emergency shutdown information, and limitations; and
12. dated results, exceptions, corrections, and final acceptance.

The test should not intentionally exceed equipment ratings or improvise unsafe conditions. Exact procedures come from the approved design and manufacturer documents. DOE/FEMP’s standby-generator operations and maintenance resources reinforce that transfer, operation, testing, and maintenance are part of readiness; they are facility-oriented guidance, not a residential test script or promise of indefinite operation.

Preserve the final load schedule, one-line, control sequence, fuel records, settings, manuals, commissioning results, permits, and inspection closeout. These documents help future technicians distinguish the designed operating plan from a later fault or unrecorded equipment change.

Choose the design path that matches the household

A selected-load design may fit a household that values a clear, predictable set of essentials and is comfortable leaving large discretionary circuits outside the backup boundary. It can make the operating promise easier to understand, but the exact selected panel and circuits still require calculation and starting review.

A managed whole-service design may fit a household that wants broader circuit availability but accepts automatic limits, delays, or shedding. It needs a precise priority schedule and commissioning. It should not be sold as unlimited whole-home operation.

A broader simultaneous-load design may fit when the household genuinely needs several large loads together and the exact generator, fuel system, transfer equipment, site, approvals, and project scope support that outcome. “Bigger” does not waive those reviews.

A deferred or revised design may be the responsible outcome when fuel deliverability, site constraints, flood requirements, equipment records, utility work, or the household’s priorities remain unresolved. A quote can identify investigation steps without pretending the final size is known.

Sunburst’s confirmed backup-generator service provides the appropriate context for property-specific load, fuel, transfer, site, permitting, installation, and testing review. It does not make one size or product correct for every home. If you want a proposal built around your actual outage priorities and equipment, request a property-specific backup assessment and bring recent electrical records, equipment labels/manuals, fuel information, and the loads you expect to remain available.

Questions to ask before accepting a generator size

Use these questions during an assessment or proposal review:

• Which exact loads and circuits are included, excluded, shed, or delayed?
• What simultaneous operating scenarios were calculated?
• Which motor or compressor start controls the design?
• What source data was used for that starting event?
• What exact generator model, fuel, rating, and site assumptions support the recommendation?
• What does the transfer switch connect, and what does its rating not prove?
• Which load-control devices are included, and what is their priority and failure behavior?
• How were gas pressure/flow or propane storage/vaporization/piping verified?
• Which provider, utility, or licensed party still must approve or change fuel equipment?
• How are future HVAC, EV, pool, well, addition, or battery changes treated?
• What permits, plan reviews, inspections, and property constraints remain open?
• What staged-load and starting-event test is included?
• What readings and control results will appear in the commissioning record?
• Which limitations will the owner receive in writing?
• Who should be called before changing backed-up equipment or controls?

The clearest proposal may recommend less nameplate capacity than another and still provide a better-defined outcome. The deciding evidence is the operating record, not the confidence of the sales presentation.

How Sunburst sizes a standby generator

A Sunburst sizing study follows the sequence above: outage priorities first, then a measured equipment record, then credible simultaneous operating states, then the motor-starting cases that usually control the answer. We keep the transfer boundary and the generator capacity as separate decisions, and we treat load shedding as an operating strategy that must be commissioned and demonstrated, not as capacity you were given for free.

South Carolina conditions push the arithmetic in specific directions. Summer outages mean HVAC is rarely optional, well pumps are common outside municipal water areas, and hurricane restoration can run for days, which makes fuel deliverability part of sizing rather than an afterthought.

Our backup generator service covers the study, the placement work, the fuel path, permits, installation and a witnessed commissioning test, backed by our lifetime full-system warranty. If your outages are short and frequent, ask us to compare battery storage at the same visit — the standby-versus-portable guide covers that trade-off. See where we work in South Carolina, then book a free assessment for a sizing study on your home.

Whole house generator sizing FAQs

Can I size a generator from my home’s square footage?

No. Square footage does not identify electrical equipment, fuel choices, motor starts, simultaneous operation, transfer boundary, or outage priorities. Two similar-size homes can require different operating plans. Use a field inventory and property-specific calculation.

Does a 200-amp service need a generator that supplies 200 amps?

Not automatically. The service rating is not a measurement of the home’s outage demand. The design must evaluate actual connected loads, applicable calculations, simultaneous operating states, starts, and controls. Transfer equipment may cover a broad service while a generator supports a managed subset at any moment.

Does “whole-house generator” mean everything can run at once?

No. The phrase is used inconsistently. Ask whether the design is selected-load, whole-service with load management, or another documented arrangement. Require a list of included loads, simultaneous operating cases, restrictions, and control priorities.

Can load shedding let me use a smaller generator?

It can reduce the capacity needed for simultaneous operation when the household accepts a documented priority strategy and the exact equipment is approved, compatible, and tested. It does not create capacity. A vague promise that controls will handle the load is insufficient.

Why can an HVAC compressor or well pump change the size?

Motors can create a short starting event above normal running demand. The important case is the exact motor starting while stated background loads operate. Use exact equipment data and generator response information rather than a universal multiplier.

Can utility interval data determine the generator size?

It can reveal demand patterns and improve the evidence, but it may miss short starts, unidentified equipment behavior, outage-only priorities, and future loads. Combine it with field records, manuals, calculations, and the proposed control sequence.

Does natural gas guarantee continuous generator operation?

No. The design must verify the generator’s fuel requirement and the property’s pressure, flow, meter/regulator, piping, and other connected loads. A gas connection is not a guarantee of supply through every outage, and this guide makes no runtime promise.

How large should a propane tank be?

There is no universal answer. The review must consider the exact generator and load plan, other propane appliances, usable storage, vaporization, temperature, regulators, piping, tank location, refill access, applicable rules, and owner expectations. A consumption table should not be presented as guaranteed runtime.

Should EV charging be included on generator power?

Only if the household has a defined outage need and the electrical, generator, fuel, transfer, and control design supports it. Many plans treat EV charging as deferrable, limited, or blocked during an outage. The choice should be explicit rather than assumed.

Is a weekly exercise proof that the generator is correctly sized?

No. Exercise can confirm limited functions under the exact exercise configuration. It may not transfer the home, apply priority loads, start the controlling motor, test shedding, or verify fuel pressure under the design condition. Acceptance and ongoing maintenance should follow the actual system documents and contract.

What documents should I keep after installation?

Keep the load inventory, sizing calculation, one-line, circuit schedule, control sequence, exact equipment data, fuel records, settings, permits, inspections, commissioning results, warranties, maintenance requirements, and owner instructions. Review them before changing major loads.

Sources and methodology

This guide was researched and updated on August 10, 2026. Project requirements can change by code cycle, jurisdiction, property, utility or fuel provider, equipment revision, and filing date.

• South Carolina Building Codes Council: code adoption
• City of Charleston: residential generator permitting guidance
• South Carolina LLR: residential electrical licensing
• South Carolina LLR: LP-gas licensing
• UL Solutions: transfer-switch certification and evaluation
• DOE/FEMP: equipment operations and maintenance summaries
• PNNL: standby-generator operations and maintenance
• FEMA: protecting building utility systems from flood damage
• CDC: carbon monoxide basics
• CPSC: stationary-generator carbon-monoxide hazard report

The technical standards and manufacturer documents for the exact project remain controlling within the adopted and approved design. The public sources above support the decision framework; they are not a substitute for an equipment-specific calculation, permit review, fuel design, or commissioning plan.