Estimate the generator surge wattage needed for connected loads. Enter their combined running watts and the largest additional startup surge for a single appliance, assuming appliances start one at a time. Defaults are illustrative; check appliance and generator ratings.
Estimate the generator’s minimum continuous power rating from the total running load and your chosen maximum loading percentage. Enter appliance running watts and any additional continuous load; defaults are illustrative. Check the generator’s continuous kW rating and allow separately for motor starting surges, power factor, altitude, temperature, and manufacturer derating.
Estimate how long a generator-powered charger will take to charge a battery using battery capacity, state of charge, charger output, and charging efficiency. Enter the charger’s actual DC charging current, not the generator’s AC current. This average-current estimate does not account for charging current tapering near full charge; actual charging may take longer.
Estimate the generator capacity in kVA for a single-phase welder using its rated maximum input voltage and current, plus any simultaneous loads and a sizing margin. Use the welder’s input ratings, not its welding output current. Check the welder and generator manufacturer recommendations for starting loads, compatibility, and derating; select the next available generator size above the estimate.
Estimate the generator’s continuous power rating from the appliances you expect to run at the same time, the largest additional starting surge, and your desired running-load reserve. Add appliance nameplate running watts, including cooking equipment, refrigeration, ventilation, and lighting. Defaults are illustrative. Select a generator with a continuous rating at least as large as the result, and verify its starting capacity, voltage, and circuit requirements with the equipment manufacturers.
Estimate the generator capacity needed for tools operating at the same time. Enter their combined running watts and the largest additional starting surge, then add a reserve. Starting surge is the extra wattage above running watts, not the motor’s total starting wattage. Use equipment ratings and select a generator with sufficient starting and continuous capacity.
Estimate weekly generator fuel spending using your generator’s fuel consumption rate, operating schedule, and local fuel price. Defaults are illustrative; fuel consumption varies with load and operating conditions.
Estimate the tank capacity needed for a generator using its fuel consumption rate, desired runtime, reserve, and usable tank capacity. Use the manufacturer’s consumption rate for the expected load. Defaults are illustrative; consumption varies with load and operating conditions.
Estimate a balanced three-phase generator’s real electrical power from line-to-line voltage, line current, and power factor. Enter actual operating values or generator ratings; defaults are illustrative. The calculation assumes balanced sinusoidal loads and does not account for derating or starting surges.
Estimate a single-phase generator’s real electrical output from voltage, current, and power factor. Enter the power factor for the connected load; the defaults are illustrative. This steady-state calculation does not account for motor starting surges or generator derating.
Estimate the AC current drawn by a load from its real power, voltage, power factor, and phase configuration. For three-phase power, enter the line-to-line voltage and total power across all phases. This estimate assumes balanced three-phase loads and does not account for starting surges. Default values are illustrative.
Estimate the maximum one-way copper cable length for a single-phase generator circuit based on an allowed voltage drop. Defaults are illustrative. This calculation uses conductor resistance at 20°C and excludes reactance, temperature effects, connections, and starting-current voltage drop. Check cable ampacity, overcurrent protection, grounding, and local electrical requirements separately.
Estimate voltage drop in a copper extension cord using one-way cord length, load current, wire gauge, and generator voltage. The calculation uses conductor resistance at approximately 20°C and assumes a single-phase circuit with current traveling through two conductors. Actual drop can be higher when the cord is hot or under motor starting loads.
Estimate the minimum generator running capacity for an electric resistance heater and other connected loads, including any additional starting surge and a chosen reserve. Enter the heater’s electrical input rating from its label. The estimate assumes all loads can run and start at the same time; compare the result with the generator’s continuous rating and round up to an available generator size. Confirm that its starting rating, voltage, and outlets also suit your equipment. Defaults are illustrative.
Estimate the generator output needed to start a refrigerator while powering other loads. Enter the refrigerator’s running and starting watts from its specifications or a suitable measurement. The estimate assumes the other loads run when the compressor starts and applies a user-selected safety margin. Generator starting and continuous ratings must each be checked separately.
Estimate the generator wattage needed to start and run a sump pump alongside other loads. Enter the pump’s running and starting watts from its specifications or measurements. The result applies a chosen reserve to the larger pump demand plus other loads. Select a generator with sufficient starting and continuous wattage ratings, rounding up to an available size.
Estimate the generator output needed to start a well pump while supplying other running loads. Enter the pump motor’s rated horsepower, estimated efficiency, starting-watt multiplier, other simultaneous loads, and desired reserve. Defaults are illustrative; motor starting requirements vary. Confirm the pump’s starting demand and the generator’s surge rating and voltage before buying.
Estimate the generator capacity needed to start and run an air conditioner alongside other loads. Enter the air conditioner’s total starting watts and running watts from its specifications or measurements, plus the watts of other appliances operating at the same time. The result includes a reserve margin and is a conservative target for the generator’s continuous watt rating. Confirm that its surge rating also covers the starting load. Defaults are illustrative; actual requirements vary.
Estimate simple payback from avoided annual costs and generator ownership costs. Enter your own estimates; defaults are illustrative. A result of 0 means annual savings do not exceed annual operating and maintenance costs, so there is no payback under these assumptions. This simple method excludes financing, taxes, inflation, and generator replacement.
Estimate the total purchase, installation, and fuel cost for a dual fuel generator over a chosen period. Enter the consumption rate and price for the fuel you expect to use: gasoline or propane. Defaults are illustrative; actual fuel use varies with electrical load. Maintenance, repairs, storage, and fuel price changes are excluded.
Compare the estimated monthly operating cost of generating electricity with the cost of buying the same energy from your utility. Defaults are illustrative; enter consumption and output figures for your generator under the expected load.
Compare estimated generator and battery costs over a chosen period. Enter purchase and installation costs, average annual use, and operating costs per hour. A positive result means the generator costs more; a negative result means the battery costs more. Defaults are illustrative. Include expected fuel, maintenance, charging, and replacement costs in your inputs as appropriate. This simplified comparison assumes constant annual use and hourly costs and excludes financing and the time value of money.
Estimate the fuel and routine maintenance cost of electricity from a generator using its actual fuel consumption and average electrical output. Default values are illustrative; enter figures for the same operating load and fuel type. Fixed ownership costs are excluded.
Estimate annual generator maintenance costs using your expected service visits, operating hours, hourly maintenance allowance, and annual repair budget. Defaults are illustrative; actual costs depend on the generator and service schedule. Avoid double-counting supplies or repairs already included in the service price.
Estimate days until your next generator oil change using your manufacturer’s recommended interval and your recent average daily runtime. Enter hours since the last oil change, or since first use if the initial oil change is due. The estimate assumes steady daily use; check the manual for initial break-in, calendar-based, and severe-use maintenance requirements. Defaults are illustrative.
Estimate the total cost of buying, installing, and operating a natural gas generator over a chosen number of hours. Enter the generator’s fuel consumption at your expected load and your delivered gas rate. Defaults are illustrative; actual consumption, installation costs, and maintenance vary.
Estimate diesel use by interpolating between your generator’s fuel consumption rates at no load and full load. Enter manufacturer data when available. This simplified estimate assumes a constant load and a straight-line relationship between the two rates; actual consumption varies with operating conditions.
Estimate generator runtime from the gasoline available, the fuel consumption rate at your expected load, and the percentage of fuel you expect to use. Runtime changes with electrical load and operating conditions; the defaults are illustrative.
Estimate the generator wattage needed to run your selected loads and start the load with the largest additional starting demand. Enter the combined running watts of all loads, including that load. Assume loads start one at a time; the margin is an illustrative allowance.
Convert real power in kilowatts (kW) to apparent power in kilovolt-amperes (kVA) using the load’s power factor. The default power factor is illustrative; use the rated or measured value for your equipment.