Free · no email required · instant
What size generator do you need —
and what will it cost?
Answer five quick questions about your home. You'll get the right whole-home generator size — sized with the same method our installers use, including the motor-start check most calculators skip — and an honest installed-cost estimate. No email, no wait.
Your recommended size
18 kW
Whole-home backup
Estimated installed cost
$11,000 – $14,000
All-in (unit, transfer switch, gas, electrical, pad, permits, labor).
Runs your whole home
- GeneracGenerac 18 kW Guardian
- KohlerKohler 18 kW (18RCAL)
Estimate only, from the same sizing method our installers use — a free assessment with a real load calculation confirms it. Not a quote.
How it sizes
Real sizing math, not a square-footage guess.
Most online calculators just divide your square footage by a number. This one runs three checks per generator model on your actual fuel: the running watts have to fit, the biggest motor has to be able to start (the locked-rotor surge naive tools ignore), and it has to pass the NEC whole-home demand calc a licensed installer would run. Then it maps the size to a real installed-cost range. More on sizing → Cost breakdown →
Free assessment
Turn your estimate into a real quote.
Free and no pressure. Tell us about your home — mention the size the calculator gave you — and a local specialist will follow up, usually the same day, with a confirmed size and an all-in price for Dallas.
Prefer to talk? (855) 997-1213How accurate is this generator sizing calculator?
It runs the same sizing method our installers use — an OEM running-watts worksheet, a motor-start (locked-rotor) check that naive calculators skip, and an NEC 220.83 whole-home demand calc — against real Generac and Kohler spec data on your actual fuel (natural gas ratings are lower than propane). It's an honest estimate for planning, not a final quote: a free assessment with a real load calculation at your home confirms the exact size.
How much does the recommended generator cost?
The calculator shows an all-in installed range for your recommended size — typically $8,000–$15,000+ for a whole-home standby in the Dallas area, covering the unit, automatic transfer switch, gas line, electrical, pad, permits, and labor. Bigger homes and longer gas runs land higher. We give you the real number for your home after the assessment.
Why does natural gas change the size I need?
Every air-cooled generator makes less power on natural gas than on propane — a Generac '22 kW' is about 21 kW on gas, and a Kohler '14 kW' is only 12 kW. The calculator uses the correct rating for the fuel you pick, which is why the honest answer can differ from a spec-sheet headline.
What's 'whole-home with smart load management'?
It means the recommended size runs your whole home as long as a load-management transfer switch staggers the big 240-volt loads (a second AC, the EV charger, the water heater) so they never all pull at once. It's how mid-size units are legally sold as whole-home under NEC 702.4 — you get full coverage without jumping to the largest, most expensive unit.
Sizing uses Generac and Kohler published spec data (NG/LP ratings, motor starting kVA) and standard OEM + NEC 220.83 methods, verified July 2026. Cost ranges are installed all-in estimates and vary by home. This tool is for planning, not a specific offer or quote.