AESV planning tool

Stop Guessing. Size Your Backup Power System in Minutes.

Estimate your backup power needs, battery capacity, solar panel size, and charge-controller rating in a few minutes. Start with your real loads, get a plain-English planning estimate, and use the result to compare the right guides and products.

01

Start with your real loads

Add appliances or paste a known daily load to get a fast sizing estimate.

02

See your backup target

Get battery, solar array, and controller guidance in plain English — no jargon first.

03

Save or compare the result

Email the report, then compare the result with the next AESV guide before you buy.

Best for: homeowner backup planning, solar kit comparisons, and early off-grid sizing.
Step 1

List what you want to power

Choose one input method: list appliances, or use a known daily load if you already have it.

or


1 kWh = 1,000 Wh. A small cabin might use 1,000–3,000 Wh/day; essential home backup often starts around 5,000 Wh/day. When the known-load box is checked, the appliance table is ignored.

Step 2

Choose system settings



If you don’t know your local peak sun hours, use this rough starting point: sunny regions 5–6, mixed regions 4–5, cloudier regions 3–4. These are planning shortcuts, not exact rules.


How we calculate your numbers (worked example)

Here is exactly what the calculator does behind the scenes, using a real example:

Example: A fridge (150 W x 8 h) + Wi-Fi router (15 W x 24 h) = 1,200 + 360 = 1,560 Wh/day.

  • Battery target = 1,560 Wh x 1.5 (reserve factor) x 1.5 days backup = 3,510 Wh. The 1.5x reserve accounts for depth-of-discharge limits (most batteries should not be drained fully) and real-world charging losses. At 24V, that is about 146 Ah.
  • Solar array = 1,560 Wh / 5 sun hours x 1.25 (margin) = 390 W of panels. The 25% margin covers heat, wiring losses, and less-than-ideal panel angles.
  • Charge controller = 390 W / 24V x 1.25 = about 20 A. We round up to the next standard controller class.

Your actual numbers will differ based on the appliances you select and the settings you choose.

Limitations and safety notes
  • This is an educational planning tool, not a substitute for a professional load analysis or electrical design.
  • The calculator does not account for motor startup surges (compressors, pumps, power tools can draw 2-3x their rated wattage for a few seconds).
  • Sun hours vary by season, latitude, shading, and panel orientation. The default of 5 hours is a rough annual average for mixed U.S. climates.
  • Battery performance degrades in extreme cold or heat. LiFePO4 batteries may need low-temperature charging protection below 32 F (0 C).
  • The calculator does not size wiring, fuses, breakers, or inverters. Those depend on installation details that only a qualified installer can assess.
  • Always have a licensed electrician or solar installer verify your system design before purchasing equipment or beginning installation.

Planning note: this calculator gives an educational estimate for early product research. Permanent electrical systems should be checked by a qualified electrician or solar installer.