How to complete lighting load calculations (NEC 2017 and 2020 Table 220.12)

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July 24 2025

Lighting was one of the first uses of electricity and it’s still a core part of any electrical load calculation today. Even though it seems simple, lighting loads can be surprisingly complex. The rules for completing proper lighting load calculations vary depending on whether the project is residential or commercial and there are different requirements for different types of lighting. In this post, we’ll break it all down to make it easy to calculate the lighting load for your next project.

How do you calculate a lighting load?

For a dwelling, multiply the square footage by 3 VA, then apply the demand factors in Table 220.45 (NEC 2023) or Table 220.42 (NEC 2020 and 2017). For commercial projects, use the VA per square foot for the occupancy type, then apply the same demand factor tables. Kopperfield's load calculator applies these demand factors and lookups automatically.

Residential lighting load calculations (dwelling units)

For most homes, lighting load calculations are straightforward. The NEC allows you to use a general unit load factor of 3 VA per square foot, so you don’t have to count or quantify each light fixture. This includes track lighting: there’s no need to count this separately unless there is something really unusual about the lighting setup. Just take the square footage, multiply by 3, and you’re done with the base load.

Once you’ve calculated the initial lighting load, you can then apply a demand factor. In NEC 2023, you’ll find these in Table 220.45. For NEC 2020 and 2017, refer to Table 220.42.

What is the demand factor for dwelling lighting?

For dwelling units, the first 3,000 VA is taken at 100%, 3,001 to 120,000 VA at 35%, and anything over 120,000 VA at 25%. For a 2,000 sq ft home, 2,000 × 3 VA = 6,000 VA. The first 3,000 VA stays at 3,000 VA, and the remaining 3,000 VA at 35% is 1,050 VA, for a lighting load of 4,050 VA.

Commercial lighting load calculations (non-dwelling)

Commercial projects require a bit more attention to detail to calculate the lighting load. First, you’ll need to figure out whether you’re calculating for general lighting based on occupancy type or for specific lighting devices. Each path has different rules.

General lighting

For general lighting, check Table 220.42 (NEC 2023) or Table 220.12 (NEC 2020 and 2017) to find the required volt-ampere per square foot based on occupancy type (like offices, restaurants, warehouses, etc.). There can be significant differences between code years, so make sure you’re using the NEC edition your jurisdiction requires. For example, the VA value for schools/universities and sports arenas changed from 3VA/sqft in 2020 to 1.5VA/sqft in 2023.

Once you’ve calculated the total lighting load, you can again apply the demand factors from Table 220.45 (NEC 2023) or Table 220.42 (NEC 2020 and 2017).

Specific lighting devices

For specific lighting types, you’ll need to reference other parts of Article 220. Some special scenarios are listed below.

Show-window lighting: NEC 220.46 requires at least 200 VA per linear foot (or 660 VA per linear meter) measured along the base.
Track lighting (outside of dwelling units or hotel rooms): NEC 220.46 requires 150 VA per 2 feet of track. If the track is powered through a current-limiting device, you can use the device rating instead.
Other lighting loads: NEC 220.14 includes other lighting types like luminaires (where you use the maximum VA rating of the fixture), heavy-duty lampholders (where you count 600 VA minimum per outlet), and sign and outline lighting (where you use 1200 VA per required branch circuit per 600.5(A)).

These rules are consistent across NEC 2017, 2020, and 2023 editions, though it’s always worth confirming all calculations with your codebook to be sure.

How do you convert a lighting load to amps?

Divide the calculated VA by the system voltage. The 4,050 VA dwelling lighting load above on a 240V service works out to about 16.9 amps.

Avoid overestimating lighting loads

We’ve seen electricians overestimate lighting loads when they don’t have demand factors or code tables handy. Sometimes it helps to play it safe, but this can lead to unnecessary costs and complexity. With the right tools and code knowledge, you can calculate with confidence and build smarter to save time and money for you and your clients.

At Kopperfield, every lighting load calc, residential or commercial, automatically applies NEC demand factors and lookups based on your inputs. Whether it’s track lighting or show windows, our load calculator has it covered. Tens of thousands of electricians have already run load calculations through our tool to get the correct lighting load out of the box. For the rest of Article 220, see our NEC Article 220 quick guide.

Lighting load calculation FAQ

Do I count light fixtures in a dwelling load calc?

No. Dwellings use a general unit load of 3 VA per square foot, so you don’t count individual fixtures.

Which table has the lighting demand factors in NEC 2023?

Table 220.45. In NEC 2020 and 2017 it’s Table 220.42.

Do I count track lighting separately in a house?

No. In dwelling units, track lighting is covered by the 3 VA per square foot general lighting load.

Updated September 2026. Originally published July 24, 2025.

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