Home project math and what it costs to run your home.
Turn room measurements into gallons, boxes and bags, and look up what electricity costs in your state, what an appliance costs to run and what it costs to charge an EV at home. Official data, dated, with the arithmetic shown.
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Where electricity costs the most and least
All 50 states and DC →Highest residential rates, July 2026
| State | ¢ per kWh | 900 kWh costs |
|---|---|---|
| Hawaii | 48.00 | $432.00 |
| California | 33.61 | $302.49 |
| Maine | 32.41 | $291.69 |
| Massachusetts | 30.49 | $274.41 |
| New York | 29.90 | $269.10 |
Lowest residential rates, July 2026
| State | ¢ per kWh | 900 kWh costs |
|---|---|---|
| Louisiana | 12.72 | $114.48 |
| Nevada | 12.77 | $114.93 |
| Utah | 13.12 | $118.08 |
| North Dakota | 13.41 | $120.69 |
| Tennessee | 13.71 | $123.39 |
900 kWh × the state's average price, which already blends fixed charges and taxes. Your tariff can differ; the average bill by state shows typical use as well as price.
Average electric bill by state
Monthly use, price and bill for every state, from Hawaii's $212.12 to New Mexico's $92.88 (2024).
Compare bills ↗ APPLIANCESCost to run an appliance
Watts × hours × your rate. A 1,500 W space heater run 4 hours a day costs $32.96 a month at the U.S. average.
Price an appliance ↗ EV CHARGINGCost to charge an EV at home
Cost per 100 and 1,000 miles in every state, with EPA efficiency ratings and a gasoline comparison.
Check your state ↗Material calculators
One project. One clear shopping list.
Paint a room. Or a few.
Add rooms, subtract measured openings, and build separate wall, ceiling and primer orders.
Open paint calculator ↗ PLANKS, TILES & BOXESGet the flooring order right.
Include cuts and overage, round up to full boxes, and compare material costs.
Open flooring calculator ↗ BEDS, BORDERS & YARDSWork out bags versus bulk.
Convert bed area and chosen depth into volume, then compare bag and delivery prices.
Open mulch calculator ↗ SLABS, POST HOLES & STEPSCount concrete bags or yards.
Add each pour, then compare 40–90 lb bag counts with a ready-mix order and delivery fee.
Open concrete calculator ↗How many gallons for a 12 × 10 ft room?
Walls: 2 × (12 + 10) × 8 ft = 352 sq ft. Subtract 40 sq ft of measured doors and windows: 312 sq ft. Two coats: 624 sq ft. At a label coverage of 350 sq ft per gallon, 624 ÷ 350 = 1.78 gallons, so buy 2 gallons. There is no extra allowance in that figure; add one if the surface is rough or the color change is large.
See the 12 × 12 room worked in full →Guides by topic
All 20 guides →Home energy costs
Electricity prices and average bills for every state from the U.S. Energy Information Administration, plus the cost to run appliances and charge an EV at home.
Paint, primer and surfaces
Manufacturer spread rates, primer and coat counts, and worked quantities for rooms, cabinets, exteriors, fences and decks.
- How Many Square Feet Does a Gallon of Paint Cover? Manufacturer Spread Rates Compared
- How Much Exterior Paint for a House: Measure Walls and Gables, Not Floor Area
- How Much Paint for a 10x10 Room
- How Much Paint for a 12x12 Room?
- How Much Paint for a 2-Car Garage Interior
Flooring, boxes and overage
Square footage, overage and carton rounding, L-shaped rooms, stairs, bathroom tile and underlayment.
Mulch, soil and outdoor projects
University extension guidance on mulch depth and raised-bed soil, bags per yard, tree rings and patio-base gravel.
Your measurements. The label's numbers. Official data.
Energy figures come from the U.S. Energy Information Administration, the Department of Energy, ENERGY STAR and fueleconomy.gov, and every table states the month or year it covers. Coverage and waste figures come from the product label or supplier, and the calculators let you change every assumption before you shop.
These are cost and quantity estimates, not installation, electrical or structural advice. Manufacturer instructions take priority.
How we research, cite and correct →