Watts to Amps kWh Cost Amp Hours to kWh Voltage Drop
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Size any electrical system in under a minute.

Batteries, solar, inverters, panel upgrades, server racks, EV chargers — every calculator is transparent, tuned for accuracy, and shows the formula behind the answer.

Popular: Battery Sizing kWh Cost Watts to Amps EV Charger Load Voltage Drop
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9 tools

Solar & Battery

Size PV arrays, battery banks, inverters, and charge controllers for on- and off-grid systems.

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10 tools

RV & Backup Power

Van life, shore power, generators, outage runtime, and emergency planning.

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9 tools

Home & Homelab

EV chargers, panel upgrades, circuit breakers, UPS sizing, rack & GPU power.

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9 tools

Quick Tools & Learn

Watts ↔ amps, kWh cost, voltage drop — plus a methodology page.

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All 37 tools

Solar & Battery

9 calculators
Solar Payback Calculator Popular
Years to break even on a PV install.
Battery Sizing Calculator Popular
Usable kWh + Ah for your daily load.
Powerwall Sizing →
How many units cover your home.
Backup Hours →
Runtime of any battery bank.
Solar Panel Sizing →
Array watts to match your draw.
Off-Grid System →
Full stack sized together.
Inverter Sizing →
Continuous & surge watts.
Charge Controller →
MPPT amps for your array.
Time-of-Use Savings →
Dollars saved shifting load off-peak.

RV & Backup Power

10 calculators
RV Battery Sizing Popular
Ah for your fridge + lights + fans.
Van Life Solar →
Roof-mount PV for mobile living.
RV Inverter Sizing →
Pure-sine watts for appliances.
Shore Power →
30 A vs 50 A — what you need.
Generator Sizing →
kW to carry starting loads.
Home Battery Backup →
Whole-home vs essentials only.
Emergency Planner →
72-hour outage load breakdown.
Power Station Sizing →
Jackery / Ecoflow class picker.
Generator vs Battery →
Cost & runtime head-to-head.
Outage Runtime →
Hours a given pack will last.

Home & Homelab

9 calculators
EV Charger Load Popular
Service impact of a L2 charger.
Panel Upgrade →
When 100 A stops being enough.
Home Load →
NEC-style total connected load.
Circuit Breaker Sizing →
Amp rating for a given circuit.
Server Power →
Watts per host + PDU loading.
UPS Sizing →
VA + runtime for your rack.
Rack Power →
Circuit planning for 42U.
PUE Calculator →
Data-center efficiency ratio.
GPU Power →
PSU headroom for multi-GPU rigs.

Quick Tools & Learn

9 items
Watts to Amps Popular
DC / AC conversion, single instant.
kWh Cost Popular
Monthly dollars for any load.
Amp Hours to kWh →
Convert battery spec sheets.
Solar Production →
Daily kWh by location & tilt.
Battery Runtime →
Hours from Ah + load.
kW to kWh →
Power → energy over time.
Voltage Drop →
% loss across a wire run.
Peak Sun Hours →
PSH by US region.
Methodology →
How we calculate everything.

Why PowerSizing

Transparent math

Every calculator shows its formula, inputs, and assumptions. No black boxes, no affiliate pressure.

All 37 tools publish their equation

Under 30 seconds

Compact, above-the-fold inputs. Answer & nearest standard part appear the moment you finish typing.

Median time to result: 24 s

Built for real installs

Defaults reflect NEC practice, LiFePO4 realities, and honest round-trip losses — not marketing numbers.

How a calculation works

Every tool follows the same flow.

Enter what you know

Daily load, voltage, chemistry, runtime. We fill in safe defaults if you're missing a value.

See the formula

The equation and each input's role are visible as you type. Tooltips explain technical terms.

Get nearest real-world part

We round up to standard pack, wire gauge, or breaker size — not a theoretical minimum.

New to electrical sizing?

Our methodology page walks through DoD, round-trip efficiency, NEC derating, peak sun hours, and more — with plain-language examples. Read it once, use the calculators forever.

Read the methodology