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27 free calculators. No sign-up.
Size it right.
Know what it costs to run.
Answer a few questions about your home. Get the exact size you need, what it costs to run at your state's electric rate, and the short list of models that actually fit.
- Show-my-math on every result
- EIA 2025 rates for all 50 states
- Ranked by fit, not by commission
- Nothing you type leaves your browser
What are you sizing?
Pick one. It takes about a minute.
Backup Power
Generators, home batteries and power stations sized to your outage.
Generator Size Calculator
Running and starting watts for your outage loads, inverter vs open frame, hookup options, matched models.
Open calculatorHome Battery Backup Sizer
How many kWh and kW your essential circuits need for a multi-day outage, and which systems fit.
Open calculatorPower Station Size Calculator
Watt-hours for a CPAP, fridge, camping trip or van, plus how long any unit will run your gear.
Open calculatorGenerator Fuel Calculator
Gallons of gas and tanks of propane per day for 20 generators at your load, and what an outage costs.
Open calculatorEV Charger Size Calculator
Charger amps for your daily miles, the breaker it needs, monthly charging cost, and chargers that fit your car's plug.
Open calculatorWater
Softeners and filters sized to your hardness, iron and household.
Water Softener Size Calculator
Grain capacity from your hardness, iron and household size, then matched systems for city or well water.
Open calculatorTankless Water Heater Size Calculator
GPM and BTU from the fixtures you run at once and your groundwater temperature, then heaters that deliver it.
Open calculatorBuying guideBest Reverse Osmosis System and What Each Gallon Costs
Reverse osmosis systems ranked by filter cost per gallon, waste water, flow and install: tankless, tank and no-install countertop picks.
See the picksBuying guideUnder Sink Water Filter vs Reverse Osmosis: Which Do You Need?
A carbon under-sink filter costs about 4 cents a gallon and fixes taste. RO costs about 10 cents and removes dissolved solids. Which you need.
See the picksHeating & Air
AC BTU and purifier CADR for your room, and what they cost to run.
AC BTU Calculator
BTU for any room from the ENERGY STAR chart, what it costs to run, and window or mini-split units that fit.
Open calculatorAir Purifier Size Calculator
The CADR your room needs, the yearly cost of power and filters, and purifiers that clear it.
Open calculatorPool Heat Pump Size Calculator
BTU for your pool and temperature rise, what it costs per hour to run, and heat pumps that fit.
Open calculatorDehumidifier Size Calculator
Pints per day for a basement, crawlspace or room, the drain setup that fits, and the monthly cost to run.
Open calculatorSmart Home & Robots
Gadgets that pay for themselves, and robots sized to your lawn, floors and pool.
Smart Thermostat Savings Calculator
What a smart thermostat saves on your heating and cooling, and how many months each model takes to pay back.
Open calculatorRobot Lawn Mower Size Calculator
Rated lawn area, slope and navigation your yard needs, and the robot mowers that fit.
Open calculatorRobot Vacuum Finder
Whether your home needs LiDAR, a self-emptying dock or a mop, and the robots that have them.
Open calculatorRobotic Pool Cleaner Finder
Pool robots rated for your pool size and type, with walls, waterline, corded or cordless.
Open calculatorCordless Vacuum Finder
The runtime your home needs, anti-tangle brushes for pets, and stick vacuums that deliver.
Open calculatorHobby Rooms
Golf simulators, home theaters, game rooms, bars, aquariums and grow rooms, sized to your space.
Grow Tent and Indoor Greenhouse Sizer
Tent size, grow light watts and fan CFM for your vegetables, herbs or seedlings, and the monthly cost to run.
Open calculatorGolf Simulator Room Size Calculator
Whether your ceiling clears a driver swing, which launch monitors fit the depth, the screen size and where the projector mounts.
Open calculatorAquarium Size and Cost Calculator
Real gallons, filled weight and floor load, filter and reef flow, heater watts and the monthly cost to run any tank.
Open calculatorGame Room Size Calculator
Which pool table, ping pong, shuffleboard and dart setups fit your room, laid out to scale, plus home bowling lane lengths.
Open calculatorHome Training Range Planner
Whether your room fits dry fire or a 10 m airgun lane, target scaling, and a pellet trap rated for your airgun.
Open calculatorHome Theater Size Calculator
Screen size from your seats, projector throw, riser height, the Atmos speaker layout and a receiver that runs it.
Open calculatorHome Bar and Speakeasy Size Calculator
Bar length for your stools, the room it takes, kegerator taps, ice per party, bar tools and glassware, and the hidden bookcase door size.
Open calculatorWine Cellar Calculator
Cooling unit size from your room's cubic feet, how many bottles the walls hold, racks, door seals and the cost to run.
Open calculatorHome Security
Cameras, doorbells, locks, alarms and AI deterrents, planned around your doors and yard.
Home Security Planner
How many cameras, which doorbell, lock and alarm, and whether you need a monthly plan, from your home's layout.
Open calculatorBuying guideBest Security Cameras With No Subscription (Local Storage)
Security cameras that record to a microSD card or a local recorder with no monthly plan: battery, solar, floodlight, indoor and wired 4K systems.
See the picksBuying guideAI Guard Dogs, Robot Dogs and Home Deterrents: What Actually Exists
Electronic watchdogs that bark when someone approaches, a real robot dog, home patrol robots, and floodlight cameras with sirens: what each one does and does not do.
See the picksBuying guideBest DIY Home Security System With No Monthly Fee
DIY alarm kits, video doorbells and smart locks that work without a paid plan, plus which popular systems do need one and what you get for it.
See the picksCost to Run
What any appliance costs at your state's electric rate.
Appliance Cost to Run Calculator
What any appliance costs per hour, day and month at your state's electricity rate.
Open calculatorElectricity Rates by State
Every state's average residential rate from the EIA, ranked.
Open calculatorBuying guideCheapest Space Heaters to Run: Why the Thermostat Matters More Than the Brand
Every 1,500 W heater costs about 26 cents an hour at the US average. Thermostats, low-watt settings and heating one room are what cut the bill.
See the picksBuying guideHow Much Does Heated Flooring Cost to Run?
Electric heated floors cost about 38 cents per heated sq ft a month, about $19 for a 50 sq ft bathroom. The math, plus kits with thermostats by size.
See the picksPicks the calculators land on most
Each one earns its spot with a sizing fact, not an opinion. Run the matching calculator to confirm the fit for your house.
Jackery Explorer 1000 v2
- 1.1 kWh
- 1,500 W continuous
About 2.5 nights of CPAP per charge or 16 hours on a full-size fridge, at around 24 lb.
- Lightest 1 kWh class unit in our list at 23.8 lb
- About 17 hours of a full-size fridge per charge
- 1,500 W inverter runs a coffee maker or small microwave
- 400 W solar input, lowest of the 1 kWh class
- Three AC outlets
$250 to $500, live price on Amazon
Check price on AmazonPaid link. We earn a commission at no cost to you.
Westinghouse iGen2550DFc Dual Fuel Inverter
- 1,900 W running
- 2,550 W starting
- gasoline / propane
- inverter
+1 moreFewer
- 52 dBA
Runs a fridge, furnace blower, router and lights on gas or a grill tank, with CO shutoff.
- Runs a fridge, furnace blower and lights
- Dual fuel: gas or propane
- CO sensor and a 52 dBA noise level
- 1,700 W on propane, less than on gas
- Pull start only, no 240V outlet
$500 to $1,000, live price on Amazon
Check price on AmazonPaid link. We earn a commission at no cost to you.
Anker SOLIX F3800 Plus
- 3.8 kWh
- expands to 27 kWh
- 6,000 W continuous
- 120/240V
120/240V split phase, 3.8 kWh expandable to 26.9 kWh, starts a 1/2 HP well pump without fuel.
- 120/240V split phase, so it can run 240V loads like a well pump
- 9,000 W surge covers a 1/2 HP well pump start
- 3,200 W solar input, more than the original F3800 (2,400 W)
- 137 lb, plan to keep it in one place
- 20 ms switchover, slower than the 0 ms Jackery Explorer 5000 Plus
About $2,400 at Anker SOLIX, checked Oct 13, 2026
Check price at Anker SOLIXPaid link. We earn a commission at no cost to you.
Westinghouse WGen9500DF Dual Fuel
- 9,500 W running
- 12,500 W starting
- gasoline / propane
- 74 dBA
9,500 W running with a 14-50R 240V outlet for an interlock kit or transfer switch, dual fuel, with CO shutoff.
- 9,500 W on gas, 8,500 W on propane
- 14-50R and L14-30R outlets, remote start
- 12,500 starting watts starts a well pump with the house loads running
- Not an inverter, loud at 74 dBA
- No CO sensor on this version
$500 to $1,000, live price on Amazon
Check price on AmazonPaid link. We earn a commission at no cost to you.
AFWFilters Fleck 5600SXT 48,000 Grain Softener (10% crosslink resin)
- 48,000 grain
- 12 GPM
48,000 grains with a metered Fleck valve covers 4 people at 15 gpg with a weekly regen.
- Fleck 5600SXT metered valve
- 1.5 cu ft of 10% crosslink resin
- Bypass and brine tank included
- DIY kit, you handle the install
- No carbon stage for chlorine taste
$500 to $1,000, live price on Amazon
Check price on AmazonPaid link. We earn a commission at no cost to you.
Whirlpool WHES40E 40,000 Grain Softener
- 40,000 grain
- 8.5 GPM
40,000 grain cabinet unit for city water in a 1-bathroom home (8.5 GPM); the cheapest real softener here.
- Handles up to 10 ppm clear-water iron
- Up to 125 gpg hardness, for 1 to 5+ people
- Compact single-cabinet design
- 8.5 GPM flow, below the two-tank 48K units
$500 to $1,000, live price on Amazon
Check price on AmazonPaid link. We earn a commission at no cost to you.
Paid links are marked on each card. Amazon prices change, so we show a range and link to the live price. See the disclosure.
Quick answers
The short version of the questions people ask most, each backed by a full guide or calculator.
- Jackery vs EcoFlow vs BLUETTI: which should I buy?
- BLUETTI gives the most battery, inverter and solar input per dollar, EcoFlow is the one to pick if you want a system that grows into whole-home 240V backup, and Jackery is the lightest and simplest at a given capacity.
- Full brand comparison
- What should go in a power outage kit?
- Start with $100 to $250 of basics (light, phone power, a fridge thermometer and 7 gallons of water), add a 1 kWh power station for the fridge if outages here last a day or more, and buy a dual fuel generator only if you need a gas furnace or a well pump running.
- The tier-by-tier checklist
- How much gas does a generator use per day?
- A 3,500 to 5,000 W inverter generator running a fridge, lights and a furnace blower burns about 5 to 7 gallons of gas a day, while a large open-frame unit running a well pump and more can burn 12 to 20 gallons.
- Generator fuel calculator
- What is the best portable generator for home backup?
- For a fridge, furnace blower, lights and internet, the Westinghouse iGen5000DFc; add a 240V well pump or window AC and step up to the iGen8200TFc; for close to the whole panel, the DuroMax XP13000HXT.
- Generators by load tier
- What is the best solar generator for home backup?
- For most homes the Anker SOLIX F3800 Plus: 3,840 Wh, 6,000 W and 120/240V from one box, expandable to 26,880 Wh. If you only need the fridge, router and lights, the EcoFlow DELTA 2 Max does it with 2,048 Wh.
- Solar generators by tier
Buying guides
Best-of lists built from the same spec database the calculators use.
Cheapest Power Station Per Watt-Hour: Most Battery for the Money
Every LiFePO4 power station we list ranked by price per watt-hour. The FOSSiBOT F3600 Pro is $0.31/Wh, about 2.5 days of fridge for around $1,199.
Backup powerCheapest Solar Panels for a Power Station (Cost per Watt)
Rigid panels cost about $0.62 a watt vs $1+ for folding ones. Matched panel kits for 500 W, 1,000 W and 2,000 W power stations, with the daily Wh math.
Backup powerFOSSiBOT vs BLUETTI: Which Power Station to Buy
FOSSiBOT vs BLUETTI at 1 kWh, 2 kWh and 3+ kWh: price per Wh, inverter, solar input, UPS speed and weight, with fridge hours per charge.
Backup powerHow Long Does a 20 lb Propane Tank Last on a Generator?
A 20 lb tank runs a mid-size dual fuel generator about 10 to 12 hours at 1,500 W. Hours per tank for 16 generators, and how many tanks a 3-day outage takes.
Backup powerJackery vs EcoFlow vs BLUETTI: Which Brand to Buy
Jackery vs EcoFlow vs BLUETTI compared at 1 kWh, 2 kWh and whole-home size. Real specs, prices and which brand fits CPAP, fridge, camping or solar.
Backup powerEcoFlow DELTA 3 Plus vs Jackery Explorer 1000 v2
DELTA 3 Plus vs Explorer 1000 v2 spec by spec: capacity, watts, solar, UPS, weight, expansion and price, plus which one to buy for CPAP, fridge or camping.
Backup powerPower Outage Kit Checklist: What to Buy, Tier by Tier
The power outage kit to buy before the next storm: a small basics kit, a power station for the fridge, a generator for heat and well water, and long-outage gear.
Backup powerBest Heat Source for a Power Outage: What Keeps You Warm
The best heat in a power outage is your gas furnace on a generator or big battery. Then indoor-safe propane heaters and electric blankets, with the math.
Where the picks come from
I built these tools after one too many calculators told me I needed "2,400 watt-hours" and then left me alone with 300 listings that never said whether they could start a well pump. Watts times hours is the easy bit. Knowing which unit clears your surge, has a 240V outlet, or handles 2 ppm of iron on a well is the part that takes a spec sheet.
So each tool checks your numbers against a list of current models I keep up to date: capacity, continuous and surge output, flow rate, fuel, noise. It shows the two or three that fit and says why, using your own figures.
Running costs use the U.S. Energy Information Administration's 2025 average residential rate for your state. The national figure is 17.3 cents per kWh, but North Dakota pays under 12 and Hawaii over 40, so the state matters. If you know the rate on your bill, type it in and the math uses that.
Marcus Reed, who builds and maintains the site. More about how it works
A few ground rules
Every result has a show-my-math panel so you can redo it by hand.
Some links pay a commission, and the card says so. The tool ranks by fit and price and does not know what any link pays.
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