Choose an outage day, not an advertising label
Picture a winter evening without utility power. The refrigerator cycles, your heating equipment starts, and a pump may run while someone heats dinner. A generator must handle the agreed combination of loads. A list of everything in the house is less useful than a clear description of what you expect to use during that evening.
Write down what cannot wait: heat, water, basement drainage, food refrigeration and the outlets you rely on. Then list what you could pause, such as a clothes dryer, pool heater or vehicle charger. These are planning categories, not a promise that any particular generator can run your equipment.
A gas furnace and a heat pump deserve different conversations. The furnace still has electrical components. A heat pump may also have electric auxiliary heat. Read the heat-pump backup planning page before assuming that the heating circuit is a small load.
Make a load list the installer can actually use
| Equipment | Record safely | Decision to make |
|---|---|---|
| Heating and cooling | Model numbers; fuel; number of systems | Which zones must work at the same time? |
| Pumps | Pump and controller models; voltage if documented | What happens if the pump cannot start? |
| Kitchen | Appliances used during an outage | Can cooking loads be staggered? |
| Other large loads | Water heater, dryer, EV charger, workshop equipment | Essential, optional, or excluded? |
Photograph accessible equipment labels without removing electrical covers or entering an unsafe space. A breaker label is a clue to a circuit, not a measurement of the appliance’s actual demand. If the panel schedule is incomplete, mark it as unknown rather than guessing.
Running demand and starting demand answer different questions
Running demand describes power used after equipment is operating. Motor starting can require a different short-term demand. Generac’s professional sizing tool separates motor starting requirements from the other loads. That distinction explains why adding appliance running watts is only an initial exercise.
Here is an illustrative planning example, not a sizing recommendation: two households have the same floor area. One needs a refrigerator, a furnace blower and selected outlets. The other needs a well pump, two cooling systems and electric auxiliary heat. The shared floor area hides the decisions that matter. The equipment list makes those decisions visible.
Ask the installer which motor start was used in the calculation and which other loads were assumed to be running when it starts. You should be able to read that assumption in the proposal. A final calculation must consider the equipment and rules applicable to the installation.
Decide what load management is allowed to pause
Load management can delay or disconnect selected loads so that higher-priority equipment has capacity. A whole-panel connection with managed circuits is different from a guarantee that every appliance can operate simultaneously. The transfer-switch comparison explains those choices.
- Name each circuit that may be managed, rather than accepting “load shedding included.”
- Ask whether heating stages, water heating or vehicle charging change during an outage.
- Request a description of restart order after a load is paused.
- Consider a future appliance separately; do not treat spare capacity as established without a revised calculation.
If you work from home, include the router and relevant outlets in the circuit list. Powering them does not guarantee that the internet provider’s network will stay available. For equipment needed for health or safety, develop a separate continuity plan with the relevant provider; a household generator can fail or require maintenance.
Compare the rating for the fuel you will use
Use the selected model’s specification sheet, including its rating on your proposed fuel. Do not compare a brochure’s most prominent number against a different model’s natural-gas rating without checking the underlying specifications. Your fuel supply and electrical design must be evaluated together.
The natural-gas and propane guide helps you prepare supply questions. Neither fuel choice removes the need for a site visit and a documented design.
Leave the assessment with four written answers
- The generator model and rated output on the proposed fuel.
- The backed-up circuits and any loads excluded or managed.
- The design assumptions for the largest motor starts and concurrent loads.
- The limitations you will need to follow during an outage.
Take those answers into the quote comparison checklist. If two bids describe different backup coverage, their prices are not yet comparable. Send your equipment list with an installation inquiry so the conversation starts with your actual priorities.
Sources and scope
Prepared from the primary sources below. Equipment manuals and the responsible local authority control the requirements for your specific project; this page is a planning aid, not an installation procedure.