Guides
Solar Sizing & System Calculators
How many panels, how many watts, how many kilowatt-hours — the sizing math behind every solar system, worked out step by step. This category extends our free wattage calculator from appliance-level loads to whole-system sizing: panel arrays, battery banks, and solar for a multi-day outage.
Solar sizing guides
How Many Solar Panels Do I Need to Run My House?
For an average U.S. home: 17 to 25 panels, or roughly 7 to 9 kW. Here is the formula behind that, and why your location moves the answer more than your house does.
Read guide →How Many Watts of Solar Do You Need to Charge a 100Ah Battery?
Roughly 300-400W for a 12V LiFePO4 100Ah battery in one good day — but the answer changes with battery chemistry, sun hours and your charge controller. Full math inside.
Read guide →How to Calculate Your Home's Daily kWh Usage Before Going Solar
Every solar quote starts with this number, and installer estimates are often built on national averages rather than your house. Getting it right takes ten minutes.
Read guide →Solar + Battery Sizing for a 72-Hour Power Outage
Your annual daily-average kWh is the wrong number for outage planning. Here is how to size a critical-loads system for three days, including the winter-storm case that breaks most estimates.
Read guide →Solar Panel Wattage Explained: What 100W, 200W, and 400W Actually Mean
A 100W panel does not give you 100 watts. Here is what the number on the label actually measures, and what each wattage tier realistically produces.
Read guide →How Many Solar Panels Do You Need for a Tiny House?
Most tiny houses need 800W to 1,600W of solar — a fraction of a full home. Here is how to size it from your actual loads rather than a rule of thumb.
Read guide →Solar Panel Sizing for a 200 Amp Service: Full Breakdown
Your electrical panel, not your roof, is often what caps system size. Here is the 120% rule, the ~7.6 kW ceiling it creates on a 200A service, and the four ways around it.
Read guide →Solar System Size Calculator: kWh, Panels, and Battery in One Place
The complete sizing sequence in one walkthrough — from your utility bill to a panel count, an inverter rating and a battery size, with the formula at each step.
Read guide →⚠️ All figures in this category are typical industry averages for planning purposes. Always confirm exact wattage against your own appliance's nameplate rating before sizing backup power.