What it calculates
Estimate a rough residential service demand for early planning.
Service Size Planning Calculator
Create a rough early-stage residential service demand estimate from connected loads and a demand factor.
Planning and estimating aid only. Verify project requirements, manufacturer instructions, adopted codes, permits, and field conditions before performing regulated work.
Electrical planning
How to Use This Calculator
Use the field units shown below, then compare your result with the worked example. Changing the percentage to make a result fit a preferred service does not validate that service.
How the calculation works
Connected load is reduced by the user-entered planning demand factor, then divided by service voltage and compared with common service sizes.
What the result means
This is intentionally a rough planning tool and is not a substitute for a code-compliant service/load calculation.
Understand the demand percentage input
An entered 24,000 watts at a user-selected 50% demand basis becomes 12,000 watts. Dividing by 240 volts gives 50 amps. The stored reference-size list then returns 60 amps as its next listed step.
Contractor tip: Changing the percentage to make a result fit a preferred service does not validate that service. Use the actual applicable load-calculation method and review the equipment and utility requirements.
Verify the final quantity
The demand percentage is your assumption. This model does not derive permitted demand factors, account for all required loads or verify the utility service. Its reference step is not a code-compliant service calculation.
Good practice: Compare the calculated quantity with plans, specifications, product packaging and current field conditions before purchasing material.