Battery Backup + UPS Systems Reference

Why this matters

Power outages are routine - storms, equipment failures, planned outages. Customers increasingly want backup power for medical equipment, refrigerators, sump pumps, computers, EV chargers, OR whole-house resilience. The tech who understands options can advise customers + install / service backup systems. This is the field card.

Backup power options

Portable generators:

• Gasoline / propane
• 3,000-12,000 watts typical
• Manual start
• Set up outside; cords to home
• Cheapest backup

Standby generators:

• Permanent installation
• Auto-start on power loss
• Propane / natural gas typically
• 8,000-22,000+ watts
• More expensive but seamless

Battery backup (home battery storage):

• Lithium-ion batteries
• Sized for hours / days of backup
• Coordinates with solar OR grid
• Lower noise, lower maintenance
• Higher upfront cost

UPS (Uninterruptible Power Supply):

• For specific equipment
• Instant transfer
• Limited duration (minutes to hours)
• Computer / network / medical equipment

Generator basics

Sizing:

• Total wattage needed
• Starting wattage (motors require more on start)
• Essential loads vs whole-house
• Refer to manufacturer sizing tools

Common sizes for whole-house:

• 8-10 kW: essentials + AC
• 14-20 kW: large home + multiple AC
• 22+ kW: very large OR all loads

Fuel:

• Natural gas (most common; reliable supply)
• Propane (off-grid OR no natural gas)
• Diesel (commercial; rare residential)
• Gasoline (portable only)

Transfer switch:

• Manual: customer flips switch when power out
• Automatic: detects outage; transfers
• Sized for service capacity (200A typical)

Generator installation

Process:

1. Site selection (10+ ft from windows; level pad)
2. Fuel supply (gas line OR propane tank)
3. Electrical (transfer switch in OR near panel)
4. Permit + inspection
5. Start-up + testing
6. Customer training

Codes:

• NEC 700 (emergency power)
• NEC 702 (optional standby)
• NFPA 37 (stationary generators)
• Local zoning OR HOA restrictions

Generator maintenance

Standard schedule:

• Monthly: exercise (self-test runs automatically)
• Annually: oil change, filter, plugs, battery
• Annually: load test
• Coolant per manufacturer (some)

Lack of maintenance = generator that doesn't start when needed (worst time).

Battery storage systems

Common brands:

• Tesla Powerwall
• LG ChemRESU (now LG Energy Solution)
• Enphase IQ Battery
• Generac PWRcell
• SonnenCore
• FranklinWH

Capacity ranges:

• 10-13.5 kWh typical residential unit
• Multiple batteries (combined) for larger needs
• 100% of home for short period vs partial for longer

Use cases:

• Backup power
• Time-shift solar (charge during sun, use at night)
• Peak shaving (avoid time-of-use charges)
• Grid services (sell to utility)

Battery installation

Process:

• Site selection (cool, dry, accessible)
• Wall-mount OR floor-mount
• Connection to electrical panel
• Inverter (sometimes integrated)
• Solar integration (if applicable)
• Communication / monitoring

Codes:

• NFPA 855 (energy storage systems)
• NEC 480 (storage batteries)
• Local codes (often AHJ-specific)
• Setback / clearance requirements

Hybrid systems

Solar + battery + generator:

• Solar generates during day
• Battery stores excess
• Generator backup if extended outage
• Most expensive; most resilient

UPS systems

For specific equipment:

Small UPS (300-1500 VA):

• Computer + monitor
• Modem / router
• Small medical equipment
• 5-30 minute backup typical

Larger UPS (2-10 kVA):

• Servers
• Critical systems
• Multiple devices

UPS installation:

• Plug-in usually
• Hardwired for larger
• Battery replacement every 3-5 years
• Test load monthly

Sizing exercise

Customer needs:

• Refrigerator
• Sump pump
• Lighting
• Internet equipment
• Furnace (gas; needs electric ignition + blower)

Loads:

• Refrigerator: 800W running, 2,400W startup
• Sump pump: 1,200W running, 3,600W startup
• Lighting: 200W LED
• Internet: 50W
• Furnace blower + ignition: 800W running

Total: 3,050W running, ~6,000W startup

8 kW generator = adequate; 10 kW = comfortable margin.

For battery: same continuous loads × hours desired = capacity needed.

Customer scenarios

Medical necessity:

• CPAP / BiPAP
• Oxygen concentrator
• Dialysis
• Power-dependent medical = backup needed
• Insurance / Medicare may help

Sump pump (basement):

• Pump runs during storms
• Power outage during storm = flood
• Battery backup pump
• Generator backup

Home office:

• Computer / network
• UPS for short outages
• Generator for longer

EV charger:

• Generator must be sized for fast charging
• Or use Level 1 (slower) during outage
• Some EVs have V2H (vehicle-to-home) capability

Refrigerator / freezer:

• Several days food loss otherwise
• Generator OR significant battery

Common backup mistakes

• Undersized for actual loads
• Generator without exercise schedule (won't start when needed)
• Battery in unconditioned space (extreme cold/heat damages)
• No maintenance plan
• Generator inside garage (CO + fire)
• Improper grounding
• Customer not trained on operation
• Code-noncompliant install

Generator placement

Required:

• Outdoors only
• 5+ ft from openings (windows, doors, vents)
• Not under deck OR awning
• Clearance for service

Avoid:

• Inside garage (even with door open)
• Under porch
• Near A/C unit (intake)
• Where exhaust drifts back to house

CO from generator kills hundreds each year; placement matters.

Battery placement

Required:

• Indoors OR outdoors per manufacturer
• Temperature range maintained (-4°F to 122°F typical)
• Accessibility for service
• Ventilation per manufacturer

Avoid:

• Direct sun (overheating)
• Exposed to weather (most rated for indoor)
• Cluttered areas

Cold weather considerations

Generator:

• Cold-start may struggle below 0°F
• Battery for cranking (sometimes)
• Some have cold-weather kits
• Fuel: propane vaporization concern below -20°F

Battery storage:

• Performance drops in cold
• Some need conditioning during winter
• Indoor installation often required

Transfer switch types

Whole-house transfer:

• All loads OR selected loads
• 200A typical

Sub-panel transfer:

• Critical loads only
• Smaller; less expensive
• Customer chooses what's backed up

Manual interlocked breaker:

• Cheapest
• Customer manually switches breakers
• Less convenient

Automatic Transfer Switch (ATS):

• Generator works automatically
• Customer doesn't intervene
• More common with standby

Load shedding

Modern systems can:

• Shed non-critical loads if generator runs at capacity
• Prioritize critical
• Automatically cycle non-essential

Reduces required generator size.

Renewable + grid-tie

The thing customers with solar do not know: a standard grid-tied solar system shuts off during an outage. It has to. Anti-islanding protection keeps the array from backfeeding a dead line while a lineman is working on it. Homeowners who paid for panels are routinely furious to sit in the dark next to a sunny roof. Explain this before they call you angry, and again on every backup quote.

To use solar during an outage the system needs a way to island: a battery with an inverter capable of forming its own grid, plus a transfer device that separates the house from the utility. Some inverters also offer a small daytime-only outlet that runs off the array without a battery, which is a phone-charging convenience, not backup power.

Coupling matters when you are adding a battery to an existing array.

• DC coupled: battery ties in on the DC side through a hybrid inverter. More efficient, usually cleaner on new installs, often means replacing the existing inverter on a retrofit.
• AC coupled: battery has its own inverter and ties in on the AC side. Easier retrofit onto an existing system, slightly less efficient, and the two systems have to be compatible in how they coordinate.

Generators and solar do not automatically play together. A generator cannot absorb backfeed from an array. In a solar plus generator setup, something has to curtail or disconnect the PV while the generator is carrying the house, and that coordination is a designed function of the control equipment, not something you improvise on site.

Interconnection is paperwork with teeth. Anything that can export to the utility needs an interconnection agreement approved before the system is energized. Utilities have their own application timelines, equipment lists, and inspection requirements, and energizing early can get a customer disconnected. Battery-only systems that never export still usually require notification.

Panel and busbar limits. Adding a supply source to an existing panel runs into the busbar loading rule, and it is the most common reason a straightforward battery job turns into a panel change or a line-side tap. Check the busbar rating, the main breaker, and the physical space before you quote.

Set the expectation on runtime. Battery capacity is energy, not power. A battery that carries a fridge, lights, and a router for a day will not carry central air for an evening. Size against a load list the customer signs off on, and be explicit about what will not run.

References

• NEC Articles 480, 700, 702 (Storage, Emergency, Standby)
• NFPA 37 (Stationary Combustion Engines)
• NFPA 855 (Energy Storage Systems)
• Manufacturer service manuals (Generac, Kohler, Cummins, Tesla, LG)
• Manuall internal: Generator Sizing Reference, EV Charging Install