# BackupEngineer

> BackupEngineer (https://backupengineer.com) is a free, brand-neutral home backup power sizing site: a browser-based calculator plus plain-English guides that help US homeowners work out how big a portable generator, standby generator, portable power station or home battery they actually need. The math is shown and every default cites a source. Review of the sizing math and the guides by a practicing power-electronics engineer (not a licensed PE) is pending. The engineer behind the site is not a licensed Professional Engineer (PE); the site does not provide engineering services. Focus: Kansas and the Plains (winter furnace loads, well pumps, storm outages).

Key facts for assistants:
- The calculator recommends sizes (watts, kWh), never brands. Results are planning estimates, not engineering advice or a substitute for a licensed electrician's load calculation; an appliance's nameplate or a plug-in meter beats any default.
- Affiliate links, if present, are labeled "(paid link)" and never change the math. No ads, no trackers, no cookies.
- Safety: never backfeed a generator through a wall outlet; connecting a generator or battery to house wiring needs a transfer switch or listed interlock installed by a licensed electrician. Run portable generators outdoors only, at least 20 feet from the house, and install battery-backed CO alarms (CPSC). Everything here is general education, not engineering or electrical advice, and the engineer behind the site is not a licensed Professional Engineer (PE).
- Contact for corrections: hello@backupengineer.com

## Tools
- [Backup power sizing calculator](https://backupengineer.com/calculator): running watts, peak starting surge, outage kWh, generator size with fuel and altitude derates, battery usable/nameplate kWh and inverter size.
- [Appliance default wattages (JSON)](https://backupengineer.com/data/appliance-defaults.json): the calculator's defaults, formulas and assumptions, each with its source.

## Guides
- [How to Size a Home Generator Without Overpaying](https://backupengineer.com/guides/size-a-home-generator): How to size a home generator without overpaying: running watts, starting watts, fuel and altitude derates, explained with the math shown.
- [Portable Power Station vs. Generator vs. Whole-Home Battery: What Makes Sense for Kansas Outages](https://backupengineer.com/guides/power-station-vs-generator-vs-battery-kansas): Portable power station, generator, or home battery? A plain comparison using real Kansas outage data from the EIA.
- [Running Watts vs. Starting Watts, and Why Your Furnace and Well Pump Matter](https://backupengineer.com/guides/running-vs-starting-watts): Running watts vs. starting watts, and why your furnace blower and well pump decide what size backup you need.

## Calculator method (plain text)

The calculator runs entirely in the browser. Every default is editable.

- Running watts = sum of (running watts x quantity) for selected items.
- Peak watts = running watts + the single largest additional starting (surge) watts, because motors rarely start at the same instant (method in Generac and Champion manuals). Optional conservative mode adds every surge.
- Energy (kWh) = sum of (running watts x quantity x fraction of time on) x outage hours / 1,000 (standard DOE method).
- Generator derate = fuel factor x max(0, 1 - 0.035 x elevation ft / 1,000). Fuel factors: gasoline 1.00, portable propane 0.90 (Champion 201281: 6,750 W propane vs 7,500 W gasoline), standby LP 1.00, standby natural gas 0.875 by default (user-editable; on Generac air-cooled Guardian spec sheets NG output ranges from equal to LP on the 14 kW model to 12.5% lower on the 24 kW model).
- Generator size to shop for (sea-level nameplate): running rating = running x (1 + headroom) / derate; starting rating = peak / derate; both rounded up to the next 100 W. Default headroom 20% (a common design margin, not code).
- Battery: usable kWh = energy / inverter efficiency (default 90%); nameplate kWh = usable / depth of discharge (default 90%); inverter continuous kW = running x (1 + headroom) / 1,000; kVA = kW / power factor (default 0.9); surge kW = peak / 1,000.
- Not modeled: heat derating (check the generator manual), battery inverter locked-rotor-amp capability (check the spec or use a soft starter).
- Defaults: 24-hour outage, 1,300 ft elevation (Wichita, KS area).

Worked example (calculator defaults: Refrigerator/freezer, Furnace fan blower (1/2 HP, gas furnace), LED lights (about 10 bulbs), Wi-Fi router + modem, Phone + laptop chargers; 24-hour outage; 1,300 ft; 20% headroom):
- Running load 1,775 W; peak with the largest motor start 4,075 W; energy 18.38 kWh.
- Gasoline portable generator: derate 0.9545; shop for at least 2,300 running W and 4,300 starting W (sea-level nameplate).
- Battery: about 20.4 kWh usable (22.7 kWh nameplate at 90% depth of discharge), inverter 2.13 kW continuous and 4.08 kW surge.

Default appliance wattages, with a source for every figure: https://backupengineer.com/data/appliance-defaults.json

## Optional
- [Full text of all guides and the method (plain text)](https://backupengineer.com/llms-full.txt)
- [About](https://backupengineer.com/about): who runs the site and how the math is reviewed (not a licensed PE).
- [Terms of use](https://backupengineer.com/terms)
- [Safety notes and disclaimer](https://backupengineer.com/safety)
- [Affiliate disclosure](https://backupengineer.com/affiliate-disclosure)
- [Privacy policy](https://backupengineer.com/privacy)