Recreational Vans
A runtime calculator predicts how long a power source can operate one device or an entire load profile. At its core, the tool balances stored or generated energy against the energy your equipment consumes over time. In mobile and off grid contexts, that usually means converting battery capacity to usable watt hours, then dividing by the average power draw in watts. For fuel powered sources, the same concept applies using fuel energy content and engine efficiency to predict runtime.
Good calculators let you build a realistic picture rather than a best case claim. They allow an average load plus short spikes, acknowledge that inverters waste some power as heat, and limit usable capacity to protect battery life. The goal is not a perfect number, but a forecast that holds up when temperatures dip, fans cycle, and you brew coffee at dawn.
Think in watt hours and watts. That keeps everything in the same language and avoids surprises when you mix AC and DC loads.
For a 2000 watt hour battery bank with 90 percent usable capacity and a 90 percent efficient inverter, the effective AC energy is about 1620 watt hours. A 100 watt average load projects roughly 16 hours. If the average rises to 300 watts, runtime drops to about 5 hours. The same battery feeding DC loads directly avoids inverter losses and stretches the estimate.
Fuel runtime is the sum of tank size and consumption at a given load. Many small generators quote gallons per hour versus a percentage of rated power. If a unit consumes 0.3 gallons per hour at 25 percent load on a 1 gallon tank, you can expect a bit over 3 hours. Larger loads accelerate consumption. Inverter generators often scale fuel burn with load more gracefully, leading to longer runtime at partial loads.
Paper math gives a starting point. Precision improves when you account for the way devices behave in the field and how conditions change.
Many appliances do not pull a constant wattage. A compressor fridge might average 45 watts across a day while drawing 80 watts when running and nearly zero between cycles. Build your average from measured or published duty cycles. Also budget for short surges. Induction cooktops and compressors may spike above nameplate for a moment. Surges can trip inverters if ignored, and they can skew average loads if a calculator treats them as constant draw.
Cold slows chemistry. Lithium iron phosphate can show reduced effective capacity below freezing if not heated. Lead acid batteries lose capacity in the cold and feel the Peukert effect at high discharge rates, which shortens runtime when you pull heavy loads. If you rely on a fridge or air conditioning, temperature swings can double or halve duty cycles. Smart calculators include temperature and discharge rate modifiers for a more faithful estimate.
Runtime improves when energy is replenished while you consume it. Solar input offsets daytime loads and extends battery life into evening. Alternator charging while driving can recover a sizable portion of the bank. Shore power eliminates the limitation altogether. A practical approach is to model a day by hours, add expected charging during those hours, then calculate the battery state of charge across the timeline. This turns a static runtime number into an energy budget that mirrors daily use.
Practical steps to build your own estimate
Example load profile for a travel rig
With a 3000 watt hour lithium bank, 90 percent usable, and a 90 percent efficient inverter, effective AC energy is about 2430 watt hours. That supports the 1790 watt hour day with margin. Add 400 watts of solar at an average of 4 sun hours and you might recoup around 1200 watt hours, turning that day into a net gain during bright seasons.
Common mistakes that shrink runtime
Verification beats guesswork. A plug in meter for AC and an inline shunt for DC give true numbers. Once you have real data, tweak your calculator inputs and your estimates start matching life on the road.
Planning for vans and mobile spaces brings a few extra considerations. Mounting location affects battery temperature. Cable runs add voltage drop. Ventilation matters for inverters and chargers. A calculator can remind you what is possible, while design choices determine whether you actually achieve it.
When your goal shifts from a spreadsheet to a comfortable trip, turning this math into a system plan is the next step. If you want a team to translate runtime estimates into a complete build with batteries, charging, and protective hardware sized to your habits, explore our Recreational vans. If you already know your use case and want a ground up approach shaped around your appliances and travel rhythm, see our Custom build van path. Looking for a financed platform that still meets a calculated power target, consider our Mainstream vans options.
Runtime calculators tell you what your lifestyle demands. OZK Customs designs and builds the system that delivers it. From energy models to installation and testing, we turn numbers into quiet power and long days off grid. Reach out and let us map your loads, size your bank, and specify charging so you can travel with confidence.
Ready to turn calculations into a dependable build. Talk with OZK Customs to design a power system that matches your real runtime needs, from batteries to solar to inverters. Schedule your consult and get a tailored plan.
ADDRESS:
6159 E Huntsville Rd, Fayetteville, AR 72701
PHONE:
(479) 326-9200
EMAIL:
info@ozkvans.com