The right standby generator size depends on what you want to power, not just the size of the house. A provider should review your electrical loads, fuel source, HVAC equipment, well pump, major appliances, and whether load management will be used.
Start with the backup power goal
Before thinking about kilowatts, decide which level of backup power you want:
| Goal | What it may include | Planning note |
|---|---|---|
| Essentials only | Refrigerator, lights, outlets, internet, selected medical equipment, sump or well pump | Usually lower load, but critical circuits still need review |
| Managed-load home backup | Many major circuits with controls that prevent overload | Often balances comfort and equipment size |
| Whole-home backup | Most or all household loads | May require a larger generator and careful fuel review |
This decision also affects standby generator cost, because larger or more complex systems may require more equipment and installation work.
Loads that can change the size
Some household loads draw much more power than others. Large motor loads may also need extra starting capacity. During a sizing review, expect questions about:
- Central air conditioning or heat pumps
- Electric strip heat or auxiliary heat
- Well pumps
- Electric water heaters
- Refrigerators and freezers
- Sump pumps
- Electric ranges, ovens, or dryers
- Home office, internet, or medical equipment needs
- Pool equipment or detached building loads
The final calculation should account for how equipment starts and what may run at the same time.
Why fuel source matters
The generator’s output can be affected by fuel type and fuel delivery. Natural gas systems need adequate utility service and meter capacity. Propane systems need a properly sized tank and regulator setup.
If you are not sure which fuel source fits your home, compare propane and natural gas standby generators before requesting quotes.
What to prepare before a quote visit
You do not need to solve the full load calculation yourself. You can make the visit more useful by preparing:
- Approximate home size
- Fuel source or whether you are unsure
- Electrical panel location
- HVAC type and approximate age
- Well pump or sump pump details if applicable
- A list of must-run loads
- Whether comfort loads, such as air conditioning, are required
The provider should explain whether the proposed system is whole-home, managed-load, or essentials-only.
Ask what the quoted size is designed to do
When reviewing quotes, ask each provider to describe the expected operating scenario. A generator quote should not just say a kilowatt size. It should explain what the generator is expected to power, what may be shed or managed, and what assumptions the quote uses.
After sizing is discussed, the next step is understanding the installation process and site requirements.