How do I calculate RV watt-hours per day?

Multiply each appliance's running watts by the number of hours it runs per day, then add the results together. For example, a 60 watt TV used for 3 hours is about 180 watt-hours per day.

How many amp-hours do I need for my RV?

For a 12V lithium system, daily watt-hours can be divided by about 12.8 volts to get the energy-equivalent amp-hours. A practical battery bank also needs reserve capacity and must account for charging and system losses.

How much solar do I need to replace my RV power use?

Solar size starts with the battery-side amp-hours used each day. For a 12V system, this calculator uses a practical real-world range: panel watts divided by 4 optimistically, divided by 4.5 for a middle estimate, and divided by 5 conservatively.

Can I run an RV air conditioner from batteries?

It is possible, but air conditioning is a high-demand load. Battery capacity, inverter size, starting surge, soft-start equipment and the recharge strategy should be designed together.

FREE RV POWER TOOL

RV POWER CALCULATOR.

Start with real daily loads, size the battery for your parked time, then size solar to replace what you use. Check a new system or the battery already in your RV.

NO SIGN-UP REQUIREDUse it first. Send the results to Heeler RV only if you want help.

1. Choose what you run

Turn on the loads you actually use. The wattage and hours are editable, so use the label on your appliance when you know the real number.

Solar production estimate12V real-world daily output estimate. Use conservative for shade, shoulder season or less favourable conditions.

Battery assumptionBattery estimates assume a 12.8V lithium bank with 80% usable capacity (20% reserve).

ESTIMATED DAILY ENERGY USE0 Wh/day

Choose a few loads to start building your day.

12V energy equivalent0 Ah/dayDaily watt-hours divided by 12.8V. Actual battery draw varies with equipment and losses.

Lithium battery target—Daily battery use × parked days ÷ 80% usable capacity.

Solar to replace daily use—Optimistic daily Ah × 4; typical × 4.5; conservative × 5.

Planned solar—Typical daily solar Ah ≈ panel watts ÷ 4.5.

Inverter class to review—Only relevant for selected 120V AC loads.

Selected loads0Editable appliance estimates. Check labels when possible.

Build your daily load

Once you select your appliances, this will give you a sensible starting direction rather than just a pile of numbers.

Want help turning this into a real RV system?

Your calculator results can carry straight into the Heeler RV inquiry. You will still see and control what you send.

Planning tool only. Final battery capacity, inverter sizing, solar production, DC-DC charging, converter/charger compatibility, conductor sizing and protection depend on the actual RV and equipment. High-demand loads such as air conditioning need a system-level review.

HOW IT WORKS

Calculate RV watt-hours per day

Battery sizing gets much easier once you know how much energy you actually use. Watts tell you how much power a device uses while it is running. Watt-hours tell you how much energy it uses over time.

Watts × hours used per day = watt-hours per day (Wh/day)

A 60W television used for 3 hours is about 180Wh/day. Do the same for the fridge, Starlink, furnace fan, CPAP, microwave, laptop, air conditioner and the other loads you use, then add them together.

BATTERY / SOLAR / INVERTER

What the result actually means

RV battery amp-hours

For a 12V LiFePO4 system, dividing battery-side watt-hours by 12.8V gives daily amp-hours. Multiply by the parked days you want to cover, then divide by 80% usable capacity. Solar and later driving are kept separate so they do not hide an undersized battery bank.

RV solar wattage

Solar has to replace energy, not just look impressive on a roof. The calculator uses a practical 12V real-world estimate: panel watts ÷ 4 optimistically, ÷ 4.5 for a middle estimate, or ÷ 5 conservatively. Real production still changes with season, shading, roof layout and panel temperature.

RV inverter size

Inverter size is driven more by the largest 120V loads and their starting surge than by daily watt-hours. A microwave may only run for minutes but still demand a large inverter. Air conditioning raises the bar considerably and often benefits from a compatible soft start.

COMMON QUESTIONS

RV power calculator FAQ

How accurate are the appliance wattages?

They are starting estimates. The best number is the actual wattage from the appliance label, manual or a measured value. Every watt field in the calculator is editable.

Does a 100Ah lithium battery give me 100Ah of usable power?

Not for planning here. The calculator treats 80Ah as usable and keeps 20% in reserve. Temperature, voltage limits and high-current loads can reduce real-world runtime further.

Can solar fully recharge my batteries every day?

Sometimes, but not automatically. Roof area, shade, panel orientation, season and weather can make a large difference. Solar should be considered alongside shore power, generator charging and alternator or DC-DC charging.

Can I use this for Starlink and a residential fridge?

Yes. Select Starlink / Wi-Fi and Fridge, then change the watts and hours to match your equipment and usage. Those two loads are common reasons RV owners discover their existing battery bank is smaller than their daily energy demand.

Why does the air conditioner change the recommendation so much?

A roof air conditioner is a large continuous 120V load with compressor starting demand. Running one from batteries can be done, but the battery bank, inverter, cabling, protection and recharge strategy need to be designed together.