'+rows;
}
el("genResult").hidden = true;
el("genResult").innerHTML = "";
}
document.addEventListener("click", function(e){
var add = e.target.closest("[data-add]");
if(add){
var sel = el("presetSelect");
if(sel.value === "") return;
if(sel.value === "custom"){ addLoad("Custom load", 0, 0); }
else { var p = PRESETS[+sel.value]; addLoad(p.name, p.run, p.surge); }
sel.value = "";
return;
}
var del = e.target.closest("[data-del]");
if(del){ loads.splice(+del.getAttribute("data-del"),1); renderLoads(); }
});
document.addEventListener("input", function(e){
var inp = e.target.closest(".load-row input[data-f]");
if(!inp) return;
var i = +inp.getAttribute("data-i"), f = inp.getAttribute("data-f");
loads[i][f] = f === "name" ? inp.value : Math.max(0, +inp.value || 0);
});
/* ---------- 1. Generator sizing ---------- */
// Gas: a typical portable inverter generator burns roughly 1 gal/hr per 7,000 W of
// rated output at 50% load (3,500 W class ≈ 0.5 gal/hr; 7,500 W class ≈ 1.0 gal/hr).
// Propane: ~27% less energy per gallon than gasoline (91,600 vs 125,000 BTU/gal),
// so consumption in gal-propane/hr ≈ gal-gas/hr × 1.37. A 20 lb tank holds 4.7 gal.
function sizeGenerator(){
if(!loads.length){ alert("Add at least one appliance first."); return; }
var headroom = 1 + (parseFloat(el("headroom").value) || 20)/100;
var hrsDay = Math.max(1, parseFloat(el("hrsDay").value) || 8);
var tankGal = Math.max(0.5, parseFloat(el("tankGal").value) || 4);
var runTotal = 0, maxSurge = 0, surgeItem = "", surgeRun = 0;
loads.forEach(function(l){
var r = l.run * l.qty, s = l.surge * l.qty;
runTotal += r;
if(s > maxSurge){ maxSurge = s; surgeItem = l.name; surgeRun = r; }
});
// Peak demand = all running loads + the extra surge draw of the single biggest starter
var extraSurge = Math.max(0, maxSurge - surgeRun);
var peak = runTotal + extraSurge;
var rec = ceilTo(peak * headroom, 500);
var galHr50 = rec / 7000; // gasoline gal/hr at 50% load
var runtime = tankGal / galHr50; // hours at 50% load
var proGalHr = galHr50 * 1.37;
var runtimePro = (tankGal / proGalHr);
var html = '
'+fmt(rec)+' watts recommended
'+
'
Running load '+fmt(runTotal)+' W · worst startup surge '+fmt(maxSurge)+' W ('+surgeItem+') · peak demand '+fmt(peak)+' W · +'+Math.round((headroom-1)*100)+'% headroom.
'+
'
'+
'
'+fmt(peak)+'Peak watts you actually draw
'+
'
≥ '+fmt(peak)+'Surge rating the generator needs
'+
'
'+runtime.toFixed(1)+' hGas runtime @50% load ('+tankGal+' gal tank)
'+
'
'+(galHr50*hrsDay).toFixed(1)+' gal/dayGasoline use at '+hrsDay+' h/day (50% load)
'+
'
'+runtimePro.toFixed(1)+' hPropane runtime, same tank volume
'+
'
'+(proGalHr*hrsDay*4.24).toFixed(1)+' lb/dayPropane use at '+hrsDay+' h/day (4.24 lb/gal)
'+
'
'+
'
Propane delivers ~10% less running wattage than gasoline on dual-fuel models, and propane never goes stale in storage. Runtime figures assume a steady 50% load — real use is cyclical, so expect longer.
';
var box = el("genResult"); box.hidden = false; box.innerHTML = html;
}
/* ---------- 2. Inverter sizing ---------- */
function sizeInverter(){
var cont = Math.max(0, parseFloat(el("invCont").value) || 0);
if(!cont){ alert("Enter your total continuous AC load in watts."); return; }
var kind = el("invKind").value; // resistive | motor | compressor | mixed
var f = kind === "resistive" ? 1 : kind === "motor" ? 3 : kind === "compressor" ? 4 : 2;
var surgeNeed = cont * f;
var contRec = ceilTo(cont * 1.25, 100); // 25% headroom on continuous rating
var surgeRec = ceilTo(surgeNeed * 1.1, 100);
var wireLoss = cont / 0.92 / 12; // approx DC amps drawn at 12V incl. 8% inverter loss
var box = el("invResult"); box.hidden = false;
box.innerHTML = '
'+fmt(contRec)+' W continuous · '+fmt(surgeRec)+' W surge
'+
'
'+
'
'+fmt(cont)+'Your continuous load
'+
'
'+f+'×Surge factor ('+kind+' loads)
'+
'
'+wireLoss.toFixed(0)+' ADC draw at 12 V (incl. ~8% inverter loss)
'+
'
≥ '+fmt(contRec*1.0)+'Continuous inverter rating to buy
'+
'
'+
'
Pure-sine-wave only for electronics, microwaves, and anything with a motor. Modified-sine inverters run hot and can kill compressor motors — the $40 saved is not worth it.
';
}
/* ---------- 3. Battery runtime for inverter setups ---------- */
function sizeBatteryRuntime(){
var ah = Math.max(0, parseFloat(el("btAh").value) || 0);
var v = parseFloat(el("btV").value) || 12;
var w = Math.max(1, parseFloat(el("btLoad").value) || 0);
var chem = el("btChem").value; // lifepo4 0.8 | agm 0.5
var dod = chem === "lifepo4" ? 0.80 : 0.50;
if(!ah || !w){ alert("Enter battery Ah and load watts."); return; }
var usable = ah * v * dod * 0.88; // 88% average inverter efficiency
var hrs = usable / w;
var cycles = chem === "lifepo4" ? "~3,000" : "~500";
var box = el("btResult"); box.hidden = false;
box.innerHTML = '
'+hrs.toFixed(1)+' hours of runtime
'+
'
'+
'
'+fmt(usable)+'Usable Wh (after '+Math.round(dod*100)+'% DoD + inverter loss)
'+
'
'+fmt(ah*v)+'Nameplate Wh stored
'+
'
'+fmt(w)+'Continuous AC load
'+
'
'+cycles+'Approx cycles before replacement
'+
'
'+
'
Batteries deliver less capacity at high draw rates (Peukert effect) — lead-acid especially. If your load is more than C/5 of the bank rating, knock 15% off these hours. Compare fuel costs on the generator sizing page.
';
}
/* ---------- 4. Transfer switch load planner ---------- */
function planSwitch(){
var text = el("tsCircuits").value.trim();
if(!text){ alert("List your backup circuits, one per line."); return; }
var total = 0, rows = "";
text.split("\n").forEach(function(line){
line = line.trim(); if(!line) return;
var m = line.match(/^(.*?)\s*[-–:]\s*([\d,]+)(?:\s*w(?:att)?s?)?\s*$/i);
var name = m ? m[1] : line;
var w = m ? parseFloat(m[2].replace(/,/g,"")) : 0;
total += w;
rows += '
'+name+'
'+fmt(w)+'
';
});
// Standard manual transfer switches: 30 A = 7,200 W, 50 A = 12,000 W @ 240 V (0.8 PF design margin)
var options = [ [30,7200], [50,12000], [100,24000] ];
var rec = options.find(function(o){ return o[1] >= total; });
var box = el("tsResult"); box.hidden = false;
var recTxt = rec ? rec[0]+' A / '+rec[1]+' W switch' : 'more than 24 kW — talk to an electrician about a whole-house automatic switch';
box.innerHTML = '
'+fmt(total)+' watts of backup circuits
'+
'
Circuit
Watts
'+rows+'
'+
'
Fits a '+recTxt+' (switch rating ÷ 1.25 safety must cover your total).
'+
'
Manual switches are ~$400–700 installed; automatic standby transfer switches add $2,000+. A hardwired transfer switch is required by code — never back-feed a dryer outlet.
';
}
/* ---------- init ---------- */
document.addEventListener("DOMContentLoaded", function(){
el("presetSelect").innerHTML = presetOptions();
renderLoads();
// preselect a common starter set so the tool shows something useful immediately
addLoad(PRESETS[0].name, PRESETS[0].run, PRESETS[0].surge);
addLoad(PRESETS[9].name, PRESETS[9].run, PRESETS[9].surge);
});