Energy & power

Energy and power calculators

What will this draw, and what will it cost to run? Each calculator shows where its numbers come from and runs in your browser; nothing you type is stored.

Calculators

• What Size Generator Do I Need? Calculator
  Add up running and starting watts from a manufacturer chart, adjust for propane or natural gas, see the size tier, and estimate fuel for an outage.
• Hot Tub Running Cost Calculator
  Monthly electricity by tub size, water temperature, outside air and your kWh price, with a budget solver and optional jets, water and chemicals.
• Space Heater Cost to Run Calculator
  Cost per hour, day, month and season for your heater's watts, setting and hours, at your state's latest EIA electricity price, with CPSC safety habits.

Buying guides

• Black Friday Generator Deals: What to Check Before You Buy
  Size first, then how to tell a real discount from an inflated "was" price, with a dated deals section updated each year.
• Black Friday Hot Tub Deals: What to Check Before You Buy
  Compare running cost, not just sticker price, and spot a fake markdown. Deals section updated each year.