Size it right, the first time.
Free calculators for the "what size do I actually need?" questions — generator capacity, heater running costs, AC and heating loads. Every tool shows its math, cites its sources, and tells you when bigger is not better.
Generator Size Calculator
Pick your appliances, get running watts + the one surge that decides the size. Storm-prep presets included.
Winter readySpace Heater Cost Calculator
What a 1,500 W heater really costs per hour, day, month, and season — at your electricity rate.
Winter readyHeating Cost Comparison
Electric vs gas vs propane vs oil vs heat pump — the same heat, priced five ways per million BTU.
Coming springBTU / AC Size Calculator
Cooling load from room size, sun, insulation. Live before summer so it's aged when you need it.
Why another calculator site?
Because most sizing tools online are affiliate bait: they nudge you one size up because the commission is bigger. SizerHQ tools do the opposite — they warn you when the "safe" answer oversizes, show the formula behind every number, and link the official sources (DOE, EIA, Generac sizing guides) so you can check us.
Every calculator works offline in your browser, needs no signup, and states its assumptions in plain English.