Backup Power Map - When Grid Fails

Backup Power Map V1.1

What do you need to keep running?

Build a device list and estimate the power and battery energy your plan needs. Start with the ratings on your own equipment, then compare the results with a backup system’s specifications.

1. Add your devices

Enter one row per group of identical devices. Quantity units are assumed to run together. Hours means total time drawing the entered wattage during your planned outage, not hours per day. For cycling appliances, enter actual on-time at the stated running wattage, not the entire outage duration. This simplified model omits unlisted standby loads and load changes. Check the result against measured Wh over a representative period. Do not use a whole-day average wattage to size instantaneous output.

Device category

Categories supply names only. Enter your own verified wattage; no typical appliance ratings are assumed.

2. Battery conversion (optional)

Leave unknown inputs blank. Load results work without them; a battery estimate needs all inputs and applicable evidence. No efficiency or allowance is set by default.

Inverter efficiency at planned load (%)Usable DC energy / rated energy (%)Additional DC idle draw (W)Inverter enabled time (h)Extra capacity allowance (%)Basis for a nonzero allowance

Enter 0 explicitly for no extra allowance, or for additional idle draw already included in efficiency. Do not count idle consumption twice. The DC fraction must apply to starting charge, cutoff, temperature and battery condition. An allowance adds capacity; it is not a guaranteed remaining state of charge or a code requirement.

System, source and applicable conditions

Loading planner…

Your estimate

Your backup power plan

Combined running loadIf all listed devices run together.

Device energy demandBased on the hours entered.

Conditional rated battery estimate

Output and energy screening

Minimum continuous output screenSimultaneous watts before equipment-specific headroom.

Startup output screenAll-start scenario. A watts figure alone does not establish motor-start capability.

Usable AC energy targetLoad energy plus your explicit energy allowance; not nominal battery Wh.

Assumptions and matching evidence

All listed loads may overlap. Each entered wattage applies for its entered on-time. Your nonzero capacity allowance needs an explained basis; it is not an NEC factor or a universal safety margin. A measured usable-AC energy figure must cover comparable output, temperature, battery condition and operating mode. Nominal battery Wh cannot substitute for that measurement.

Product matching needs the exact US voltage/frequency and outlet limits, continuous output, starting magnitude and duration, W/VA limits, a compatible load profile and usable AC energy evidence. Missing values remain unknown. A high advertised boost figure is not accepted as motor-start surge evidence.

Method reviewed September 12, 2026. Product records retain individual source and verification dates. This is a screening aid, not an installation design or certification.

Research a product

EcoFlow DELTA 3 Plus: US specifications and checks. This is a research link, not an automatic match. We have not established its suitability for your plan. Its manufacturer link currently earns no commission.

Before you choose a system

Check continuous output against your simultaneous running load, with appropriate operating headroom.
Verify startup power and duration, both W and VA limits where specified, battery/BMS discharge limits, voltage, frequency, individual outlet limits, and device compatibility separately. Do not treat volt-amperes (V × A) as watts without the power factor.
Battery capacity alone does not guarantee runtime. Temperature, battery condition, idle consumption, and load changes affect real results.

This is a planning estimate, not an electrical design or a guarantee of compatibility. It does not model solar recharging or fuel generators. This is not an NEC service, feeder or branch-circuit load calculation, and does not size conductors, breakers, transfer equipment or life-safety systems. Household wiring and hardwired loads need a qualified installer using the locally adopted code.

Method, sources and limits

Running load: add quantity × running input watts for devices assumed to run together. Use electrical input power, not appliance heating/cooling output. A separate plan is needed for a different simultaneous-load group.

Device energy: E (Wh) = sum of quantity × P (W) × t (hours). This assumes each listed wattage applies for its entered on-time. For varying loads, energy is the sum over the actual operating intervals; a representative energy-meter measurement is preferable to assuming a universal duty cycle. One kWh = 1,000 Wh. No loss or reserve multiplier is added to device energy.

Starting scenarios: enter TOTAL startup watts S, not additional watts. For devices with no extra startup demand, enter running watts P. For one device starting while all others run: sum(quantity × P) + max(S − P). For all devices starting together: sum(quantity × S). Generac’s worksheet uses running watts plus the largest ADDITIONAL starting watts; our first scenario uses the same arithmetic after subtracting P from total S. Blank startup fields mean unknown. These are simplified watt scenarios, not a motor-start compatibility test. Actual current, VA, waveform, voltage dip and surge duration still require equipment-specific checks.

Battery conversion: DC Wh = device Wh / inverter efficiency + additional DC idle W × inverter enabled hours. Conditional rated Wh = DC Wh × (1 + allowance) / usable DC fraction. Percent inputs are divided by 100. This assumes constant efficiency applicable to the planned load. Idle consumption must not already be included in efficiency. Evidence is required but not automatically verified. No universal loss, allowance or NEC sizing factor is assumed.

Sources reviewed September 12, 2026: U.S. EIA: watts and watthours; Virginia Tech: appliance energy and cycling loads; Generac 2024 Home Standby Buyers Guide, Wattage Worksheet (PDF page 25); Goal Zero Yeti 1500: conversion losses and operating conditions; Victron: W, VA, surge and battery limits. Manufacturer guidance is specific to its equipment; these references do not certify this calculator or make it a code-compliance assessment.

The calculator processes your entries in this page. It does not save or send your device list. Reloading clears the plan. Report a problem or suggest an improvement.