Introduction
A backup generator can cost as little as a few hundred dollars or as much as a used car. The spread isn’t random — it tracks size, type, fuel, and whether the unit simply plugs into your appliances or is permanently wired into your home. Understanding what each dollar buys keeps you from overpaying for capacity you’ll never use or under-buying and replacing the unit later.
Start with your number first: the Generator Size Calculator tells you the kW rating your loads actually need, so every price below maps to a real requirement instead of a guess. This guide covers typical planning ranges for portable and standby generators, installation costs, ongoing fuel and maintenance expenses, and the hidden cost of sizing wrong. All prices are typical U.S. planning ranges — expect real variation by region, brand, and market conditions.
What Drives Generator Cost
Five factors set the price of a backup-power system:
- Capacity (kW). Bigger engines cost more — a 22 kW standby unit is a different machine than a 3.5 kW portable.
- Type. Portable generators are self-contained and movable; inverter generators add clean, quiet power at a premium per watt; standby units are permanently installed with automatic start.
- Fuel. Gasoline units are cheapest to buy; propane and natural gas shift costs toward fuel logistics and hookup; diesel commands a premium for durability.
- Connection method. Extension cords are nearly free; a manual transfer switch plus professional install adds hundreds to low thousands; an automatic transfer switch with a standby unit is part of a multi-thousand-dollar installation.
- Installation labor and permits. Standby installs need an electrician, often a gas fitter, a concrete pad, and permits — labor is frequently 30–50% of the project total. The DIY vs. professional guide breaks down which parts you can handle yourself.
Portable Generator Costs
Portable generators in the 3.5–7.5 kW range — the band that covers most essentials-only backup plans — typically run ~$400–$1,500. Smaller units sit at the low end; larger capacity, inverter technology, electric start, and dual-fuel capability push toward the top. This buys the generator itself. What it doesn’t include:
- Heavy-duty extension cords — budget $50–$150 for outdoor-rated cords of the right gauge and length (undersized cords are a common mistake that wastes power and overheats).
- Manual transfer switch + inlet box, professionally installed — typically $500–$1,500 installed, depending on your panel and local labor rates.
- Fuel on hand — gasoline storage, stabilizer, and rotation are ongoing minor costs; a propane conversion kit or dual-fuel model adds to the purchase price.
- CO detector — battery-backed units, $25–$50 each, are non-negotiable safety equipment.
A realistic all-in budget for a well-set-up portable system for a 5–7 kW load is often $1,000–$2,500 including cords, transfer switch, and safety gear — still far below standby territory.
Standby Generator Costs
Standby (whole-home, automatic) generators in the 10–22 kW range typically cost ~$5,000–$15,000 installed. The unit itself is roughly half of that; the rest is installation:
| Cost component | Typical planning range |
|---|---|
| Standby generator unit (10–22 kW) | $2,500–$8,000 |
| Automatic transfer switch | $500–$2,000 |
| Electrician labor (wiring, permits) | $1,500–$4,000 |
| Gas line extension / hookup | $500–$2,500 |
| Concrete pad, grading, misc. | $200–$800 |
| Permits and inspections | $100–$500 |
These are planning bands, not quotes: long gas-line runs, panel upgrades, or difficult sites can push totals higher, especially in high-cost metro areas. Get multiple quotes from licensed installers. Whether a standby unit or a portable fits your situation is worked through in the fuel and equipment guide.
Ongoing Costs: Fuel and Maintenance
The purchase price is only the beginning. Budget for:
- Fuel. A portable generator at half load burns roughly 0.5–1 gallon (2–4 L) of gasoline per hour depending on size — a multi-day outage can mean dozens of gallons. Propane stores indefinitely but delivers less energy per gallon-equivalent; natural gas standby units draw from the utility line, so fuel cost shows up on the gas bill.
- Oil and filters. Oil changes every 50–100 running hours for most portables (check the manual); standby units follow manufacturer service intervals. Budget roughly $30–$80 per service, more if you pay a technician.
- Batteries and parts. Standby units need battery replacement every 2–3 years (~$100–$200). Air filters, spark plugs, and fuel filters are small but recurring.
- Annual service contracts. For standby units, many owners pay $200–$400/year for a maintenance plan that includes the scheduled exercise runs, inspection, and priority service.
- Fuel rotation. Gasoline goes stale in 3–6 months without stabilizer (12+ months with it). Rotating stored fuel into your car periodically avoids a dead generator when you need it.
The Cost of the Wrong Size
Sizing wrong has a price tag in both directions. Undersized means tripped breakers, stalled motors, and possibly a second purchase — buying twice is the most expensive mistake in this guide. Oversized means paying more upfront, then paying more every hour it runs: a large generator at light load burns disproportionately more fuel per kWh delivered, and diesel units run lightly for long periods can develop wet stacking (unburned fuel and carbon buildup in the exhaust). The common mistakes guide covers both traps in detail.
The cheapest generator is the right-sized one — which is why the sizing math comes before the shopping. A 6.5–7 kW portable covering a carefully chosen essentials list will serve most suburban outage scenarios at a fraction of standby cost; stepping up to standby buys automation and whole-house capacity, not just more watts.
Related Guides
- Complete Guide — the full sizing walkthrough with a worked example.
- Formula Explained — the sizing math behind the recommendation.
- Fuel & Equipment Guide — generator types, fuel trade-offs, and transfer switches.
- DIY vs. Professional — which installations you can do yourself and which need an electrician.
- Common Mistakes — sizing errors that waste money or leave you dark.
Get Your Number
Every cost decision starts from one number: the kW rating your loads require. Run the Generator Size Calculator on your actual appliance list, then price the generator band that fits — portable or standby — with installation, fuel, and maintenance included in the comparison.
Disclaimer: Calculator results and cost ranges are planning estimates only; actual prices vary by region, brand, dealer, and market conditions. Always verify wattage against your equipment nameplates and obtain written quotes from licensed installers for any hardwired work. Generator connections to home wiring must comply with the National Electrical Code and local code — have a licensed electrician install transfer equipment.
