Backup generator guides

Buying a generator goes wrong in a predictable order. People start with a brand instead of a load list, get sized up two classes, sign a bundled quote they can't compare, and then skip the maintenance that would have kept it running. Each of those is avoidable with about an hour of homework.

The sizing guide is the one to read first. The formula is total running watts plus the single largest starting wattage, staying at or below about 90 percent of rated capacity. Everything downstream — price, fuel cost, pad size, gas meter capacity — follows from that number.

The installation guide covers the parts that surprise people: two permits, a gas pressure test, possible utility meter upsizing, and clearance rules that mean the unit may not fit where you pictured it. Bob Vila's installation guidance cites a minimum of 5 feet from windows, doors and soffit vents, with the model's own manual and local code setting the final requirement.

The safety guide is not optional reading if you're considering a portable. CPSC counted at least 1,332 CO deaths involving portable generators from 2004 through 2021. That's the single most important number on this whole site for anyone buying a portable.

How to choose

Read sizing before you read reviews

The right size in a mid-tier brand beats the wrong size in a premium one, every time.

Treat the install guide as a contractor checklist

Permits, gas test, meter capacity, clearances. If a bidder hasn't mentioned all four, ask why.

Use the cost guide to decompose quotes

Unit, labor ($1,500–$5,000), transfer switch labor (about $1,200), pad ($50–$75 per square foot), permits ($50–$200 each). Map each bid onto those buckets.

Do the safety guide before the shopping guide for portables

If you can't commit to 20-foot outdoor placement and CO alarms, a portable is genuinely the wrong purchase.

Plan maintenance into the budget on day one

$80–$300 per visit is the price of the generator actually working in year eight.