Will It Run Lab

Tools

RV and Van Electrical Planner

For EIA’s 70 W most-used refrigerator average running all day through an inverter, 70 W × 24 h = 1,680 Wh at the load. With the site’s 0.85 planning efficiency, battery energy is 1,680 ÷ 0.85 ≈ 1,976.5 Wh, or about 164.7 Ah at 12 V. That is a daily energy budget, not a wiring plan or a test of a camper fridge.

Load Wh/day = watts × hours/day × quantity. Battery Wh/day ≈ AC load Wh/day ÷ inverter efficiency, plus DC load Wh/day. Ah/day = battery Wh/day ÷ bus volts.

Default efficiency is 0.85 and default bus voltage is 12 V. Honda running-watt rows are not day-long averages, so the planner starts those at 1 hour per day. Do not invent a van-specific wattage that is not in the cited tables.

Plan daily energy and a starting-watt check

Default bus voltage is 12 V. AC loads use the site’s 0.85 planning efficiency unless you change it. DC loads on the same bus do not use that inverter factor. This is a planning worksheet, not an electrical design or a battery-chemistry recommendation.

Battery bus and inverter

Default efficiency is 0.85, a planning assumption used on this site when a maker does not publish one. It applies to AC loads only. Do not treat it as a measured inverter curve. Days of autonomy, if entered, multiply daily battery watt-hours. There is no default depth of discharge or lithium versus AGM factor.

Loads and hours per day

Start from a cited preset or Honda row, or enter a custom load. Average presets default to 24 hours per day. Running, typical, and Honda start/run rows default to 1 hour so a running figure is not treated as a full-day average. For a DC load, watts = amps × bus volts.

EIA most-used refrigerator, 70 W average

EIA 2020 RECS Table CE5.3b, revised March 2024. 617 kWh/year ÷ 8,760 × 1,000 ≈ 70 W. This is a day-long average, not starting watts.

Your daily energy estimate

Energy at the loads
Check inputs
Battery energy per day
Check inputs
Battery amp-hours per day
Check inputs
Running watts, if on together
Check inputs
Starting, one at a time
Check inputs

Watt totals assume the selected loads can be on together, even when hours per day are lower. Starting, one at a time uses a cited or entered start figure when one is present; if starting watts are blank, they are treated as equal to running watts, so no extra start is invented.

Inputs stay in this page’s URL, not an account. Copying a link shares load names and numbers. Do not include private or medical details.

Worked example: 1,680 Wh at the load

EIA’s 2020 RECS Table CE5.3b gives the most-used refrigerator figure used by the default load: 617 kWh/year, or 617 ÷ 8,760 × 1,000 ≈ 70 W average. Because that figure already spreads cycling over the day, 24 hours is the usual period input.

  • Energy at the fridge: 70 W × 24 h = 1,680 Wh/day.
  • Energy at the battery through an inverter: 1,680 ÷ 0.85 ≈ 1,976.5 Wh/day.
  • At a 12 V bus: 1,976.5 ÷ 12 ≈ 164.7 Ah/day.

Honda’s ENERGY STAR fridge/freezer row is a different input: 192 W running and 1,200 W starting. That 192 W figure applies while the compressor is on. Multiplying it by 24 hours would overstate a typical day. Use it for the starting-watt check and for hours the compressor is actually running, or keep the EIA average for the daily energy line.

If you enter two days of autonomy, the optional total is daily battery watt-hours times two. The planner does not apply a depth-of-discharge, temperature, or lithium versus AGM factor, because those would be unsourced defaults.

What this worksheet does not size

A 12 V or 24 V amp-hour total is not a battery purchase recommendation. Available capacity depends on the bank you actually have, how far you discharge it, temperature, age, and the inverter’s behavior at low load. Wire gauge, fuses, charger current, and shore-power or solar recharge are outside this calculator.

The starting-watt line uses the same one-at-a-time method as the generator and power station wattage calculator: running total plus the largest extra start (start minus run) while the other loads stay on. Honda rows marked 240 V are flagged. A typical van inverter still has to start and run the load at the correct voltage.

There are no affiliate links on this page today. There are no buy links on this page. See our affiliate disclosure.

Sources for the cited loads

Frequently asked questions

Why does an AC load use 0.85, and a DC load does not?

The 0.85 factor is this site’s planning assumption for inverter and conversion losses when a maker does not publish one. An AC appliance is assumed to be powered through an inverter, so battery watt-hours ≈ load watt-hours ÷ 0.85. A DC load already on the same 12 V or 24 V bus does not use that inverter factor. The efficiency input is editable. It is not a measured inverter curve.

Can I multiply Honda’s 192 W refrigerator running figure by 24 hours?

Not as a day-long energy budget. Honda’s 192 W figure is a running-watt estimate while the compressor is on, not a 24-hour average. The planner defaults those rows to 1 hour per day so the running watts are not treated as continuous. Use a cycling average, such as EIA’s 70 W figure, an EnergyGuide conversion, or a measured average, for hours-per-day energy.

Does this size a lithium or AGM bank, or tell me how to wire a van?

No. This worksheet estimates daily watt-hours and amp-hours from the loads and hours you enter, plus a running and one-at-a-time starting watt check. It does not choose battery chemistry, depth of discharge, wire gauge, fuse size, or charger settings, and it is not an electrical design.