Start with this decision
Start with wattage or load, not fuel. A runtime estimate only helps if the generator or battery can safely power the load.
Fuel & Power Calculators
Plan backup power, fuel storage, battery runtime, propane use, and tool loads without guessing. These calculators are built for outages, camping, workshops, RVs, and real-world power decisions.
Updated May 2026No signup requiredBuilt for mobile
Start Here
Top backup power calculators by intent
Use this hub to move from load sizing into runtime, fuel storage, cord safety, transfer equipment, and battery backup.
Common next step
After wattage, estimate runtime and storage, then check voltage drop or transfer equipment where applicable.
Round in the useful direction
Round runtime down for essential loads and fuel storage up only within safe storage rules.
Start Here
Start with generator runtime
If you are planning for an outage, start with generator runtime, then check fuel, cords, and backup battery needs.
Generator safety note
Never run a generator indoors, in a garage, or near doors and windows. Follow the manufacturer instructions, use proper cords, and keep carbon monoxide away from living spaces.
Tools
Emergency power
Tools for outages, storms, and backup planning.
Generator Runtime CalculatorEstimate generator runtime from fuel and burn rate.Backup Power CalculatorEstimate backup energy needed for essential loads.Power Outage Runtime CalculatorEstimate runtime from stored energy and load.Whole House Generator CalculatorEstimate whole-house generator size from running and surge loads.
Tools
Batteries and backup systems
Plan watt-hours, amp-hours, and usable runtime.
Battery Runtime CalculatorEstimate how long a battery can run a device.Battery Amp Hour CalculatorConvert load and runtime into amp-hour needs.Battery Backup Duration CalculatorEstimate backup duration from watt-hours and load.RV Solar Runtime CalculatorEstimate RV solar support from battery, solar input, and load.
Tools
Fuel planning
Estimate fuel, diesel, propane, and generator reserves.
Fuel Cost CalculatorEstimate gallons and fuel cost for a trip or job.Diesel Usage CalculatorEstimate diesel use and cost from hours and burn rate.Propane Tank Runtime CalculatorEstimate propane runtime from tank size and BTU load.Portable Generator Fuel CalculatorEstimate fuel needed for a runtime target.
Tools
Workshop and tools
Plan tool loads and shop equipment runtime.
Tools
Extension cords and electrical planning
Check load amps, cord margin, and voltage drop.
Fuel and power planning checklist
- List the loads you need to power.
- Estimate runtime before buying fuel.
- Check battery capacity and usable percentage.
- Confirm extension cord ratings and voltage drop.
- Keep reserve fuel and follow storage rules.
FAQ
Common questions
Which fuel and power calculator should I start with?
For outages, start with generator runtime or backup power. For RV or camping power, start with battery runtime or solar runtime.
Should I round runtime up or down?
For safety planning, round runtime down and keep reserve fuel or backup power available.
Can these calculators replace manufacturer specs?
No. Use them for planning, then verify against generator, battery, cord, and appliance ratings.
Why does load matter so much?
Higher load usually burns more fuel and drains batteries faster, so runtime can change quickly.
Are extension cord calculators safety advice?
They are planning tools. Follow manufacturer ratings and local electrical code, and consult a qualified electrician when needed.
Topic cluster
Generator, propane, backup power, and outages
Use these related tools together for better planning instead of treating each estimate as a one-off number.
Generator Runtime CalculatorEstimate generator runtime from fuel.Propane Tank Runtime CalculatorEstimate propane runtime.Generator Sizing CalculatorEstimate generator size.Generator Wattage PlannerPlan appliance loads.Power Outage Runtime CalculatorPlan outage runtime.Battery Backup Duration CalculatorEstimate backup battery duration.UPS Runtime CalculatorEstimate UPS runtime.
Backup planning
Generators, propane, batteries, solar, food, water, and emergency cash calculators
Use these calculators to plan generator cost, maintenance, dual fuel choices, refrigerator runtime, CPAP backup, portable power stations, solar recharge, emergency food, filter capacity, and cash reserves.
Generator Fuel Cost Per Hour CalculatorEstimate generator operating cost per hour, per day, and per outage.Generator Oil Change Interval CalculatorEstimate when generator oil changes are needed during extended runtime.Dual Fuel Generator Cost CalculatorCompare gasoline and propane generator runtime and cost.Refrigerator Outage Runtime CalculatorEstimate how long a battery, power station, or generator can support a refrigerator or freezer.CPAP Battery Backup CalculatorEstimate battery size and runtime for CPAP backup power.Portable Power Station Size CalculatorEstimate power station capacity needed for devices during outages, camping, or RV use.Solar Recharge Time CalculatorEstimate how long solar panels take to recharge a battery or power station.
How to use this estimate
The fuel and power hub is for outage planning, generator sizing, fuel budgeting, battery storage, solar output, and electrical load checks. Use it to compare runtime, wattage, cord loss, and fuel cost before you rely on equipment during a trip, job, storm, or backup-power situation.
Inputs that matter most
- Running watts, surge watts, amps, volts, fuel tank size, burn rate, or battery capacity.
- Runtime target, expected load percentage, distance, energy use, or reserve fuel.
- Equipment labels and manufacturer specifications instead of guesses whenever available.
- Safety constraints such as cord rating, transfer switch requirements, ventilation, and local electrical code.
Formula and method
Fuel and power estimates usually start with load. The calculator converts load into energy use, fuel use, runtime, voltage drop, or operating cost. A useful planning formula is available capacity divided by expected use, then reduced by an efficiency or safety reserve.
A result that looks comfortable on paper can still be unsafe if cords are undersized, loads surge together, or equipment is connected incorrectly. Read the number as a planning estimate and compare it against equipment labels, breaker limits, cord ratings, and the manufacturer manual.
Worked example
Example: a household wants to run a refrigerator, freezer, modem, lights, and a furnace blower during an outage. The generator wattage planner helps total running and surge loads. The generator runtime calculator then estimates how long the selected generator can operate at that load with the fuel on hand. The fuel cost calculator can estimate the expense of storing or using that fuel over a multi-day outage.
Common planning mistakes
- Using running watts only and ignoring startup surge.
- Assuming a generator burns fuel at the same rate at every load.
- Running long extension cords without checking voltage drop and cord amp rating.
- Connecting backup power to a home without a proper transfer switch or qualified electrical guidance.
Safety and disclaimer note
Fuel, generator, battery, and electrical calculators are planning tools only. Follow manufacturer specs, use generators outdoors because of carbon monoxide risk, follow local electrical code, and consult a qualified electrician or professional for transfer switches, panels, permanent wiring, and safety-critical decisions.
FAQ
Practical questions
Which fuel or power calculator should I start with?
Start with load or wattage. Once you know the load, runtime, fuel cost, battery size, and cord voltage drop become easier to estimate.
Can generator runtime be exact?
No. Runtime changes with load, fuel quality, elevation, temperature, maintenance, and manufacturer design.
Why does surge wattage matter?
Motors and compressors can draw extra power at startup. If surge is ignored, a generator or inverter may overload even when running watts look acceptable.
Are extension cords safe for backup power?
Only when the cord is rated for the load, length, environment, and equipment. Home connections require proper transfer equipment and electrical guidance.
Do battery and solar estimates include losses?
Some calculators include practical margins, but real systems still lose energy through inverters, wiring, heat, age, and charging limits.