AI-generated conceptual editorial image of electrical-system planning beside a modern RV. It does not depict a specific WEHO model, customer installation, wiring guide, compatibility claim or performance test.
An RV inverter sizing guide should start with the highest realistic simultaneous AC load, then test every credible startup event, DC current, daily energy and battery limits. Choose waveform, voltage and frequency for the actual appliances and market. A published inverter rating is only a shortlist input; the final system still needs model-specific engineering data and installer approval.
This sequence prevents a common mistake: choosing a watt number first and trying to make the battery, BMS, cable and appliances fit afterwards. A defensible RV design keeps continuous power, momentary starting demand and daily energy as separate calculations.
What information should you collect before sizing an RV inverter?
Build one controlled load schedule. Record each appliance’s quantity, manufacturer-rated watts or VA, power factor where relevant, whether it can operate with other loads, startup magnitude and duration, daily run time, required waveform, AC voltage and frequency. Use manufacturer data or a suitable measurement for starting demand; do not insert a universal surge multiplier.
| Input | Record | Decision supported |
|---|---|---|
| Continuous demand | Quantity, rated W or VA, power factor and operating state | Highest realistic simultaneous AC load |
| Startup event | Starting W or A, duration and other loads already running | Required time-qualified overload capability |
| AC compatibility | Waveform, voltage, frequency and outlet/terminal requirement | Correct output configuration |
| Battery boundary | Chemistry, model, voltage under load, allowable usable energy | DC current and energy checks |
| BMS boundary | Continuous and peak current, permitted duration and low-voltage behavior | Whether the battery can support the event |
| Installation | Cable loop length, route, ambient, ventilation and protection basis | Model-specific installer calculation |
| Operating target | Hours per day, duty cycle and recharge opportunity | Battery-energy requirement |
Load management belongs in this table. If an interlock prevents two high-demand appliances from operating together, document that control. If the control is only a user habit, include the simultaneous state that can actually occur.
How do you calculate the continuous inverter load?
For each credible operating state, sum the loads that can run together:
P_continuous_required = max over operating states [Σ(quantity_i × continuous_watts_i)]
Sizing from only the largest appliance can miss other loads already operating. Adding every appliance regardless of operating logic can overstate the requirement. The useful value is the highest documented simultaneous state. This state-based method follows primary manufacturer selection guidance that distinguishes continuous load from peak demand.
Keep headroom as a project decision, not a hidden percentage. State what the allowance covers—future loads, measurement uncertainty or operating margin—and require engineering to confirm how ambient temperature, ventilation and the selected model’s continuous rating affect that allowance.
How should an RV startup event be checked?
Motors, compressors and some electronic power supplies can demand more power while starting than during steady operation. Both the magnitude and duration of the event matter. For each starting load, calculate:
P_start_event = Σ(other loads already running) + verified starting demand of the starting load(s)
Then compare the event with a candidate inverter’s time-qualified overload or peak envelope. If two loads may start together, model that case or document the interlock that prevents it. Do not assume that “2× peak” automatically starts a refrigerator, air conditioner, pump, microwave or any other appliance.
The current mapped WEHO pages publish peak watts, but they do not publish peak duration or appliance-specific start tests. That means the public pages can support a shortlist, not a finished startup approval. Ask for the selected model’s overload-versus-time data and compare it with the appliance manufacturer’s starting requirement or a suitable measurement.
How do you estimate battery-side DC current?
At a defined AC operating point, use:
I_DC_est = P_AC / (V_DC_under_load × η_operating_point)
V_DC_under_load is the voltage at the inverter terminals while loaded, not only the battery’s nominal label. η_operating_point must apply at the relevant load, voltage and temperature. The two mapped WEHO pages publish 90% as maximum efficiency, not a full efficiency curve or a guaranteed value at every operating point.
The table below therefore uses 90% only as a transparent best-case nominal screening assumption. It is derived from published page ratings and the stated maximum efficiency.
| Published page rating | 12 V nominal | 24 V nominal | 48 V nominal |
|---|---|---|---|
| 1000 W | 92.6 A | 46.3 A | 23.1 A |
| 1200 W | 111.1 A | 55.6 A | 27.8 A |
Best-case nominal screening using the product pages’ 90% maximum efficiency; not a cable, fuse, BMS, runtime or configuration value.
Actual current can be higher if voltage at the inverter terminals falls below nominal or efficiency is below the published maximum. Never turn these screening values into a fuse rating, conductor size, BMS recommendation or guaranteed operating current.
How do you estimate daily battery energy and runtime?
Energy starts with each appliance’s power and operating time:
E_AC_i = P_i × run_time_i
E_AC_total = Σ(E_AC_i)
A transparent battery-side estimate keeps conversion loss and inverter idle energy visible:
E_DC_required = Σ(E_AC_i / η_i) + Σ(V_idle × I_no_load × idle_time)
Then apply battery-manufacturer limits:
E_usable_required = E_DC_required / permitted_usable_fraction
Ah_required ≈ E_usable_required / V_battery_basis
Power multiplied by time gives watt-hours, and converting watt-hours to amp-hours requires a declared voltage basis. Runtime still depends on battery voltage under load, allowable depth of discharge, BMS limits, temperature, discharge rate, battery condition, inverter load-point efficiency, no-load draw, cable drop and duty cycle. Primary battery-monitor documentation also explains that effective battery capacity varies with discharge behavior, so nameplate Ah alone is not a runtime guarantee.
This is why the old fixed expression (Battery Ah × 12 V × 0.9) ÷ Watts should not be used as a universal answer. It hides the battery’s usable fraction and treats one efficiency assumption as though it applied to every operating point.
Which waveform, voltage and frequency should you specify?
Record each load’s waveform requirement from its manufacturer. Do not claim that one waveform is safe for every device. For a focused comparison, see WEHO’s guide to pure sine versus modified sine for RV loads.
Also specify the target AC voltage and frequency, outlet or terminal form, and the battery system’s DC voltage range. A higher nominal DC voltage reduces nominal current for the same power, as the screening table shows, but that does not approve a particular WEHO configuration. Confirm the exact ordered model, DC input range and AC output group before quotation.
Which published WEHO products fit this shortlist?
The current public pages support two pure-sine reference points for this buyer task. Both pages include vehicles and RVs in their application lists, but that positioning is not proof of compatibility with every appliance, battery, BMS or installation.
| Published WEHO page | Page-level evidence | Correct procurement question |
|---|---|---|
| 1000W 12V 24V 48V Dc Ac 110V 220V Pure sine wave power inverter | 1000 W rated, 2000 W peak, pure-sine output, 50/60 Hz options and 90% maximum efficiency. | Does the exact input/output configuration and time-qualified overload envelope satisfy the documented load case? |
| 1200W 12V 24V 48V Dc Ac 110V 220V Pure sine wave power inverter | 1200 W rated, 2400 W peak, pure-sine output, 50/60 Hz options and 90% maximum efficiency. | Does the larger continuous rating close the load case without exceeding battery, BMS and installation limits? |
Authentic WEHO 1000W product asset from the current product catalog, provided separately for product identification.
The 1000 W and 1200 W pages group multiple DC-input and AC-output options, and the 1200 W table contains an unresolved model-cell inconsistency. Do not state that every AC-output version is available with every DC-input voltage. Confirm the exact model number and configuration in the quotation.
What must be verified before either inverter is approved?
Use this release checklist for the exact proposed model:
- Complete simultaneous-load schedule and highest continuous state.
- Every credible startup magnitude and duration, including other loads already running.
- Selected model’s continuous and time-qualified overload capability.
- Exact DC input range and minimum voltage at the inverter terminals under load.
- Exact AC voltage, frequency, waveform and outlet or terminal arrangement.
- Load-point efficiency and no-load consumption for the intended conditions.
- Battery model, chemistry, usable-energy limit and BMS continuous/peak current envelope.
- Positive and negative cable loop length, conductor material, route and allowable voltage drop.
- DC protection type, voltage rating, interrupt rating and location.
- Mounting, ventilation, ambient temperature, grounding/neutral/transfer arrangement and applicable RV/electrical rules.
Manufacturer installation documentation illustrates why battery capacity, cable cross-section and external protection have to be treated as model-specific engineering decisions. Do not copy another manufacturer’s cable or fuse table onto a WEHO product. Obtain the selected WEHO manual, battery/BMS documentation and local installer calculation.
For operating practices after a system has been engineered, use the separate power inverter operating guide. This page remains the owner of the RV sizing task.
What should an RV inverter RFQ contain?
Send WEHO one controlled requirement pack rather than a watt-only question. Include the load schedule, startup records, target market and AC output, battery/BMS documentation, required runtime, recharge opportunity, cable loop and mounting constraints, ambient conditions and any shore-power or transfer requirement.
Ask the response to identify the exact model and configuration, documents reviewed, open assumptions, required validation and acceptance evidence. Until peak duration, configuration availability, efficiency/load behavior and system-side limits are confirmed, describe the products as candidates—not guaranteed solutions.
FAQ
Is a 1000 W inverter enough for an RV?
Not from the headline rating alone. Compare the 1000 W continuous rating with the highest simultaneous load, then check each startup magnitude and duration, battery/BMS current and the exact model configuration. The public page does not prove compatibility with a particular appliance.
Can I use a universal 2× surge rule?
No. Starting demand varies by appliance, control method and event duration. Use manufacturer data or an appropriate measurement, include the loads already running, and compare the result with time-qualified inverter data.
How much battery current does a 1200 W inverter draw?
Current depends on voltage at the inverter terminals and efficiency at that operating point. Using 12 V nominal and the page’s 90% maximum gives 111.1 A as a best-case screening value, not a guaranteed current or design value.
How long will an RV battery run an inverter?
There is no reliable answer from Ah and load watts alone. Calculate AC watt-hours, conversion and idle energy, then apply the battery maker’s usable-energy, discharge-rate, temperature and BMS limits. Cable drop, battery condition and duty cycle also matter.
Can the published 2000 W or 2400 W peak rating guarantee compressor startup?
No. The mapped pages do not publish peak duration or an appliance-specific start test. Obtain the exact model’s overload-versus-time data and the appliance’s verified starting event before approval.
Next step
Complete the load schedule and battery/BMS worksheet, then send WEHO the exact RV operating case. WEHO can review the 1000 W and 1200 W candidates against a checkable requirement without turning a page-level rating into an unsupported compatibility promise.
Author: WEHO Power Applications Editorial Team Review status: Independently reviewed for technical accuracy, SEO/GEO, semantics and image provenance Modified: 2026-09-02 Review due: 2027-03-02
