{
  "slug": "inverter-sizing",
  "title": "Inverter Sizing Calculator",
  "heading": "Solar/Battery Inverter Sizing Calculator",
  "category": "other",
  "url": "https://www.revenuelab.fyi/toolbox/inverter-sizing",
  "summary": "Continuous and surge capacity needed for your loads or array.",
  "description": "An inverter has to satisfy two separate ratings: continuous power (what it can sustain indefinitely) and surge power (a short burst, usually a few seconds, for motor startup). Undersizing either one causes nuisance shutdowns or failure to start equipment at all. This calculator checks your planned continuous load and largest motor surge against a candidate inverter's specs, and separately checks DC-to-AC sizing ratio if you're pairing the inverter with a solar array (a ratio of 1.1-1.3 DC:AC is normal and intentional, not an error, since panels rarely hit rated output simultaneously).",
  "formula": "DC:AC ratio = array DC watts ÷ inverter AC rating; surge check = motor surge watts ≤ inverter surge rating.",
  "dateModified": "2026-09-30",
  "run_url": "https://www.revenuelab.fyi/api/public/calc?tool=inverter-sizing",
  "inputs": [
    {
      "id": "continuousLoadW",
      "label": "Total continuous load",
      "kind": "number",
      "hint": null,
      "default": 3500,
      "unit": "W",
      "min": 100,
      "max": null
    },
    {
      "id": "largestMotorSurgeW",
      "label": "Largest motor surge watts",
      "kind": "number",
      "hint": null,
      "default": 4500,
      "unit": "W",
      "min": 0,
      "max": null
    },
    {
      "id": "inverterContinuousW",
      "label": "Candidate inverter continuous rating",
      "kind": "number",
      "hint": null,
      "default": 5000,
      "unit": "W",
      "min": 500,
      "max": null
    },
    {
      "id": "inverterSurgeW",
      "label": "Candidate inverter surge rating",
      "kind": "number",
      "hint": null,
      "default": 10000,
      "unit": "W",
      "min": 500,
      "max": null
    },
    {
      "id": "arrayDcW",
      "label": "Solar array size (if paired)",
      "kind": "number",
      "hint": null,
      "default": 6000,
      "unit": "W",
      "min": 0,
      "max": null
    }
  ],
  "outputs": [
    {
      "id": "dcAcRatio",
      "label": "DC:AC ratio",
      "format": "decimal",
      "hint": null,
      "primary": true
    },
    {
      "id": "continuousOk",
      "label": "Continuous load fits? (1=yes)",
      "format": "number",
      "hint": null,
      "primary": false
    },
    {
      "id": "surgeOk",
      "label": "Surge load fits? (1=yes)",
      "format": "number",
      "hint": null,
      "primary": false
    },
    {
      "id": "headroomW",
      "label": "Continuous power headroom",
      "format": "number",
      "hint": null,
      "primary": false
    },
    {
      "id": "ratioHealthy",
      "label": "DC:AC ratio in normal range? (1=yes)",
      "format": "number",
      "hint": null,
      "primary": false
    }
  ],
  "worked_example": {
    "inputs": [
      "Total continuous load: 3500 W",
      "Largest motor surge watts: 4500 W",
      "Candidate inverter continuous rating: 5000 W",
      "Candidate inverter surge rating: 10000 W",
      "Solar array size (if paired): 6000 W"
    ],
    "outputs": [
      "DC:AC ratio: 1.2",
      "Continuous load fits? (1=yes): 1",
      "Surge load fits? (1=yes): 1",
      "Continuous power headroom: 1,500",
      "DC:AC ratio in normal range? (1=yes): 1"
    ]
  },
  "how_to": {
    "title": "How to use this",
    "steps": [
      "Enter total continuous load (W).",
      "Enter largest motor surge watts (W).",
      "Enter candidate inverter continuous rating (W).",
      "Enter candidate inverter surge rating (W).",
      "Enter solar array size (if paired) (W).",
      "Read your dc:ac ratio on the right — it updates as you type.",
      "Hit Share to keep the scenario or send it to someone."
    ]
  },
  "scenarios": [
    {
      "name": "Conservative",
      "description": "Lower-end numbers — what if things land soft?",
      "values": {
        "continuousLoadW": 2100,
        "largestMotorSurgeW": 2750,
        "inverterContinuousW": 3000,
        "inverterSurgeW": 6000,
        "arrayDcW": 3500
      }
    },
    {
      "name": "Typical",
      "description": "Defaults — the most common real-world setup.",
      "values": {
        "continuousLoadW": 3500,
        "largestMotorSurgeW": 4500,
        "inverterContinuousW": 5000,
        "inverterSurgeW": 10000,
        "arrayDcW": 6000
      }
    },
    {
      "name": "Ambitious",
      "description": "Higher-end numbers — what if things really pop?",
      "values": {
        "continuousLoadW": 5600,
        "largestMotorSurgeW": 7250,
        "inverterContinuousW": 8000,
        "inverterSurgeW": 16000,
        "arrayDcW": 9500
      }
    }
  ],
  "limitations": [
    "Estimates assume standard, average conditions — local rules, pricing, and materials vary.",
    "Results are rounded for readability; add a buffer before ordering, booking, or committing.",
    "Double-check anything with a real cost attached against a local quote."
  ],
  "faq": [
    {
      "q": "Why would you intentionally oversize the DC array relative to the inverter?",
      "a": "Panels almost never produce their full rated output simultaneously except under ideal conditions (cool temps, perfect sun angle, clean panels), so a 1.1-1.3 DC:AC ratio 'clips' only a tiny amount of peak production on the best days while letting you use a smaller, cheaper inverter that's still adequately sized for real-world production the rest of the time."
    },
    {
      "q": "What happens if the DC:AC ratio is too high?",
      "a": "Above roughly 1.35-1.4, you start losing meaningful production to clipping — the inverter simply can't pass through all the DC power the array is capable of producing at peak, wasting some of what you paid for in panels. Most designers cap the ratio around 1.25-1.30 as a sweet spot."
    },
    {
      "q": "Does surge rating matter if I don't have well pumps or AC?",
      "a": "Less critical, but still relevant for a refrigerator compressor, a table saw, or any single device with a motor — even a 700W running-load fridge compressor can surge to 1,500-2,200W for under a second at startup, and an inverter that can't cover that will trip or fail to start the load at all."
    },
    {
      "q": "How is inverter sizing different for grid-tied vs off-grid?",
      "a": "Grid-tied inverters mainly need to handle the DC:AC array ratio correctly since the grid absorbs any load imbalance; off-grid and battery-backup inverters additionally need to cover 100% of your home's actual load and surge requirements on their own, since there's no grid to lean on if the inverter is undersized."
    }
  ],
  "related": [
    "https://www.revenuelab.fyi/toolbox/off-grid-system-sizing",
    "https://www.revenuelab.fyi/toolbox/battery-backup-runtime",
    "https://www.revenuelab.fyi/toolbox/solar-array-sizing"
  ],
  "license": "CC-BY-4.0",
  "citation": "RevenueLab — Inverter Sizing Calculator (https://www.revenuelab.fyi/toolbox/inverter-sizing)"
}