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:
- Site selection (10+ ft from windows; level pad)
- Fuel supply (gas line OR propane tank)
- Electrical (transfer switch in OR near panel)
- Permit + inspection
- Start-up + testing
- 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
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