How to Size Electrical Service

An RV park may feature dozens or hundreds of electrical connection points, but no single site operates at full rated capacity continuously throughout the day.

For instance, a 50‑amp RV connection delivers substantial theoretical power, yet actual site load fluctuates drastically. RV owners may run a single air conditioner in the morning, multiple kitchen appliances in the afternoon, and full climate systems during hot evening hours.

This variable load behavior is the core reason the NEC (National Electrical Code) enforces specific demand factors for recreational vehicle parks. Instead of assuming simultaneous maximum power draw from all sites, calculations use graded demand factors based on total site quantity.

NEC compliance standards vary by code edition and local jurisdictional requirements. NEC Section 551.73 outlines standardized calculated load values and demand factors exclusively for RV park service and feeder system design.

The foundational step of RV park electrical design is compiling a complete inventory of all on‑site electrical supply facilities.

Common RV site configurations include:

• 50‑amp, 125/250‑volt receptacles
• 30‑amp, 125‑volt receptacles
• 20‑amp, 125‑volt receptacles
• Combined 30‑amp and 20‑amp supply facilities

Critical design note: The total calculated load is not the sum of all receptacle ratings on a single RV power pedestal. For single‑RV sites with multiple receptacles, calculations only reference the highest‑rated receptacle. For dual‑RV supply stations, calculations use the two highest‑rated receptacles available.

This technical distinction prevents over‑sizing electrical infrastructure, a common mistake that leads to inflated construction and equipment costs.

Per current NEC Section 551.73 provisions, standardized calculated load values for mainstream RV site configurations are listed below:

These values align with the latest NEC proposal materials and industry educational resources for RV electrical system design.

As a practical example, a 40‑site park with full 50‑amp hookups does not require 2000 total raw amps. The base calculated load equals 40 sites × 12,000 VA = 480,000 VA, before applying the official NEC demand factor.

After calculating the total base VA load for all RV sites, designers must apply the corresponding NEC demand factor based on the total number of operational sites.

Standard NEC Table 551.73 demand factors for RV parks are as follows:

Designers must note that these standard demand factors may be insufficient for regions with extreme temperatures, where heavy air conditioning or heating loads create sustained high power demand. Code‑minimum calculations do not always equal optimal real‑world operational design.

Use this real‑world case study for a 22‑site RV park with mixed configurations:

• 12 sites equipped with 50‑amp receptacles
• 10 sites equipped with 30‑amp and 20‑amp receptacles

Step‑by‑step load calculation breakdown:

A 22‑site park qualifies for a 43% NEC demand factor:

180,000 VA × 0.43 = 77,400 VA

For a standard 120/240‑volt single‑phase electrical system:

77,400 VA ÷ 240 V = 322.5 A

The final calculated service demand rounds to 323 amps. Final equipment selection requires cross‑verifying standard component ratings, conductor ampacity, utility service limits, voltage drop, and local code rules, rather than strictly matching the mathematical calculation result.

RV site load calculations only cover individual campsite power demand. Full park design requires accounting for auxiliary facility loads connected to the main service:

All auxiliary loads must be calculated independently and added to the total service load. NEC guidelines strictly separate RV site loads from building, recreational, and mechanical equipment loads. Neglecting these loads is a top cause of undersized electrical systems in newly built RV parks.

Follow this standardized 9‑step workflow for accurate, code‑compliant RV park electrical sizing:

• Step 1: Count the RV sites. Separate the sites by receptacle configuration.
• Step 2: Assign the appropriate VA value. Use the applicable NEC calculated‑load value for each site type.
• Step 3: Add the RV‑site loads. Calculate each category separately and then determine the total.
• Step 4: Apply the appropriate demand factor. Use the factor corresponding to the number of RV sites.
• Step 5: Add other building and equipment loads. Calculate shared amenities separately.
• Step 6: Convert VA to amps. For a single‑phase 120/240‑volt service, the basic relationship is: Amps = VA ÷ Volts. Three‑phase systems require specialized calculation formulas.
• Step 7: Check equipment and conductor sizing. Evaluate service equipment, feeder conductors, overcurrent protection, grounding, and neutral requirements.
• Step 8: Check voltage drop and distribution layout. Pay particular attention to long feeder runs.
• Step 9: Review future demand. Reserve 20–25% additional capacity during design for future expansion and new electrical equipment.

Critical update: Modern NEC provisions revised the 50‑amp site load value from 9,600 VA to 12,000 VA. Always verify current local code standards before finalizing project calculations.