What size whole house generator do I need for a 1000 sq ft house?
For a 1,000 sq ft house, a whole-house generator typically requires 15–20 kW capacity to power essential systems like HVAC, lighting, and appliances. Exact sizing depends on peak demand: central AC (3–4 kW), electric water heater (4.5 kW), and refrigerator (0.7 kW) cumulatively require ~12–15 kW. Opt for a generator with a 20% buffer (e.g., 18–22 kW) to handle startup surges and future needs. Pro Tip: Prioritize inverter generators for sensitive electronics and fuel efficiency.
How is generator size calculated for homes?
Generator sizing combines running watts (continuous power) and starting watts (surge power). For example, a 3-ton AC unit draws 3,500W running but 10,500W at startup. Total household demand should include all simultaneous loads, plus a 15–20% safety margin.
Deep Dive: Begin by listing all critical appliances and their wattage. Central air conditioning (3,500–5,000W), electric stoves (3,000W), and well pumps (1,500W) dominate loads. Lighting and electronics add ~1,500W. Summing these gives baseline running watts (e.g., 10,000W). Then, identify the highest starting watts (e.g., AC’s 10,500W surge) and add this to the running total. Practically speaking, a 15kW generator covers most 1,000 sq ft homes unless using electric heating. For example, a 20kW Generac unit powers a 1,200 sq ft home with two AC units and a pool pump. Pro Tip: Use a load calculation worksheet or consult an electrician for precision.
Does fuel type affect generator sizing?
Fuel type (propane, diesel, natural gas) impacts runtime and efficiency but not wattage capacity. However, natural gas generators often require larger units due to lower energy density compared to diesel.
Deep Dive: Natural gas generators provide 50–65% less energy per cubic foot than diesel, necessitating higher fuel consumption for equivalent output. For instance, a 20kW natural gas generator burns ~204 cubic feet/hour, while a diesel equivalent uses ~1.6 gallons/hour. Beyond efficiency, consider fuel availability: propane tanks require refills, whereas natural gas connects to municipal lines. But what if you’re in a remote area? Diesel’s higher energy density makes it preferable for off-grid homes. Real-world example: A 1,000 sq ft cabin using propane might opt for a 15kW dual-fuel generator, switching between propane and gasoline during shortages.
| Fuel Type | Energy Density | Typical 20kW Runtime |
|---|---|---|
| Natural Gas | 1,000 BTU/ft³ | ~10 hours (50% load) |
| Propane | 2,516 BTU/gal | ~8 hours (50% load) |
| Diesel | 137,000 BTU/gal | ~12 hours (50% load) |
RackBattery Expert Insight
FAQs
Only partially—expect to prioritize essentials (AC, fridge) and avoid high-draw appliances (electric heaters, ovens).
How much does a 20kW generator cost installed?
$5,000–$12,000, including transfer switch, fuel lines, and labor. Propane units cost 15–20% more than natural gas.