RV glossary: weights, power, towing and camping

RV ratings describe limits; measurements describe the loaded vehicle. Electrical current, energy and battery charge are different quantities. Use the term on the actual label or manual before comparing figures that only look alike; a remaining allowance is not a measured load.

Weight ratings versus actual weight

Federal vehicle definitions identify GVWR as the manufacturer’s specified loaded weight of one vehicle and GAWR as the specified axle-system capacity at the tire-ground interfaces. A higher axle total does not raise the vehicle’s GVWR.

GVW
Actual gross vehicle weight in the measured condition.
GVWR
The manufacturer’s maximum loaded vehicle weight.
GAWR
The manufacturer’s maximum load on the specified axle system.
GCWR
The manufacturer’s combined loaded-weight limit for the towing and towed vehicles.
UVW
Unloaded vehicle weight under the applicable definition; not a trip-ready scale weight.
Dry weight
A published weight description whose included fluids and equipment need checking.
CCC
Cargo carrying capacity on an RV trailer’s applicable label.
OCCC
Occupant and cargo carrying capacity on a motorhome’s applicable label.
Payload
The vehicle’s load allowance; occupants, cargo and imposed hitch load must be counted as applicable.

FMVSS 110’s RV label provisions treat onboard potable water as cargo and include full propane tanks in UVW where applicable. Do not apply an old sleeping-position subtraction formula to every current label.

An assumed 40 gallons at the label’s 8.3 lb per gallon is 332 lb. Against an assumed 1,200-lb cargo allowance, that leaves 868 lb for other applicable loads before checking axles and equipment limits.

Assumed 1,200-lb cargo allowance40 gallons of water at label convention: 332 lb; Remaining allowance: 868 lbAssumed 1,200-lb cargo allowance40 gallons of water at label convention: 332 lbRemaining allowance: 868 lb

Connections and towing

Tongue weight
Downward trailer load at a ball-type hitch.
Pin weight
Downward load imposed through a fifth-wheel or gooseneck connection.
Weight distribution
A hitch arrangement that redistributes axle loads; it does not raise vehicle ratings.
Sway control
Equipment intended to resist trailer oscillation; it does not correct an overloaded or unsuitable combination.
Breakaway
A function intended to apply the towed unit’s brakes on separation, under the installed design.
Flat towing / dinghy / toad
Transporting a second vehicle with all four wheels rolling; the toad is that towed vehicle.
Baseplate and tow bar
The vehicle-mounted connection and the bar linking it to the motorhome.
Tow dolly
A carrier supporting one axle while the other rolls, subject to both vehicles’ instructions.

Electrical quantities and equipment

Converter and inverter directionsAC supply through converter becomes DC outputThen: DC battery through inverter becomes AC outputConverter and inverter directionsAC supply through converter becomes DC outputDC battery through inverter becomes AC output
AC / DC
Alternating current / direct current.
Converter
Changes AC input to DC output; many RV units also charge the house battery.
Inverter
Changes DC input to AC output.
Amp / amp-hour
Current / charge over time. Five amps for two hours is ten amp-hours.
Watt / watt-hour
Power / energy over time. A 100-watt load for three hours uses 300 watt-hours.
Depth of discharge
The portion of stored battery charge removed; permitted use depends on the battery.
Shore power
An external electrical supply connected through the RV’s approved inlet and equipment.
Surge and running rating
A specified short-duration output and a sustained output; check the stated duration and conditions.

Water, structure and campsite language

Fresh / gray / black
Supply water / wastewater from sinks or showers / toilet wastewater. Actual tank arrangements differ.
Bypass
Plumbing that routes around a component, such as a storage water heater, under its instructions.
Anode
A sacrificial corrosion-protection part in certain water heaters; not fitted to every heater.
Slide and topper
An extending living-space section and its overhead cover; the cover is not proof against leaks.
Delamination
Separation between bonded layers.
EPDM / TPO
Different roof-membrane materials requiring compatible care products.
Full hookup
Electric, water and sewer connections at the individual site.
Dry camping / boondocking
Camping without hookups; dispersed locations also need specific land-use permission.
Pull-through / back-in
A site entered and exited forward / a site requiring backing for access.