Guides
A calculator answers one narrow question. These answer the ones around it, the sort that decide whether the number you get is the right number to be asking for.
Power & Off-Grid
4 guides- How many days of autonomy to build for Two to three days covers most off-grid homes. Each extra day costs the same as the first and gets used a handful of times a year, which is the real trade.
- Why a 100 Ah battery is not 100 Ah Depth of discharge decides what you can actually take out of a bank. It is why lead acid needs roughly twice the nameplate of lithium for the same job.
- Why 90 C wire is almost never a 90 C circuit The highest column in the ampacity table is usually off limits, because the terminations decide the rating. Then heat and bundling take more off the top.
- Where the ampacity chart stops answering the question Ampacity tells you what the wire can carry without overheating. On a long run the limit is voltage drop instead, and it lands two sizes larger.
Generators
12 guides- The biggest appliance is rarely the biggest bill Wattage is only half the story. Hours do the rest, which is how a 20 W device outspends a 1,500 W one and why audits by nameplate find the wrong culprit.
- Choosing which circuits are worth backing up A backup list is a budget decision disguised as an electrical one. Four circuits cover most of the misery, and the fifth is where the costs climb.
- Which generator fuel keeps, and for how long Petrol goes off in months, diesel in about a year, propane effectively never. That difference matters more than efficiency for a machine used twice a decade.
- How long a tank lasts, and why load decides it Run time figures on a spec sheet assume a quarter or half load. Put the house on it and the same tank empties in a fraction of the advertised hours.
- Amps to watts, and the voltage people assume Watts equals amps times volts, which is easy until you guess the voltage. Half the errors in load planning come from assuming a circuit is 120 V.
- Portable, standby, and the option in between A portable wired to an inlet and an interlock covers most of what a standby does, for a fraction of the install, and almost nobody advertises it.
- The generator is about half of what a standby install costs Transfer switch, electrical run, pad, gas connection and permits routinely match the price of the machine. Here is what each line item is doing.
- What a device costs to run, once duty cycle is in it A 2 kW heater does not cost 2 kW an hour to run. Thermostats cycle, and the share of the hour the element is actually on changes the bill by half.
- Why a 10 kVA generator gives you 8 kW Apparent power is what the windings carry, real power is what does the work, and the gap between them is power factor. The convention hides a fifth.
- Turning a kVA rating into amps you can plan with A kVA figure means nothing until you know the voltage and the phases. The three phase formula carries a square root, and missing it is a large error.
- Square footage does not size a generator Most sizing guides map floor area to kilowatts. A 3,000 sq ft house on gas heat needs less backup than a small all-electric one. Size it by what starts.
- Running watts, starting watts, and the arithmetic in between The usual advice is to add the highest starting wattage to your running total. That double-counts, and the correction changes which generator you buy.
Maker & Craft
4 guides- Swapping an oil means recalculating the lye Every oil takes a different amount of lye to saponify. Substituting gram for gram without rerunning the numbers is how a mild recipe turns caustic.
- What superfat actually buys you in a bar Superfat is deliberate leftover oil, and it is also your safety margin against a weighing error. Five percent is the default for reasons worth knowing.
- How deep you can pour resin in one go Pour past a resin's depth limit and the batch heats itself. That is what cracks a river table, yellows a cast and sometimes smokes in the cup.
- Why a resin pour stays sticky Sticky resin is almost always a ratio problem, and the usual culprit is mixing by volume a resin that is specified by weight. The two are not the same.
Home & Yard
8 guides- Why a heavier seeding rate gives you a thinner lawn Seed rates differ by species because seed size differs enormously. Sowing tall fescue at a bluegrass rate, or double any rate, costs you the lawn.
- Why a mulch order comes up short Most short orders come from measuring the bed and forgetting the depth, or from buying bags by the look of the pile. The arithmetic is two numbers wide.
- How deep mulch should be, and the depth that kills trees Two to three inches does everything mulch is for. Past four it starts working against you, and piled against a trunk it quietly kills the tree.
- How far a gallon of paint really goes The 350 square feet on the tin is a lab figure on smooth primed drywall. Texture, porosity and colour change all eat into it, and here is by how much.
- When a wall needs primer and when it does not Primer is not a rule, it is an answer to four specific wall problems. If your wall has none of them, a self-priming paint is genuinely enough.
- Soil temperature decides when to seed, not the calendar Late August to mid September suits most cool season lawns, but the reason is soil temperature. A thermometer beats a date in any unusual year.
- Bagged concrete or a ready-mix truck Ready-mix looks far cheaper per yard until the short-load fee lands. Here is the arithmetic on both, and the volume where buying bags stops making sense.
- How much concrete a fence post actually needs Two bags per post is an answer to one specific hole. Here is what changes it, why hole width matters more than depth, and how to work out your own figure.
Pets & Animals
4 guides- Why the feeding guide on the bag overfeeds most cats Label portions are built around an average cat that barely exists. A neutered indoor cat burns far less, and the gap is around a fifth of the bowl.
- Why a cat has to lose weight slowly Cats are not small dogs on this. Drop their intake sharply and the liver can fail, so the safe pace is half a percent to one percent of body weight a week.
- What the bone and organ shares in 80/10/10 are doing Bone is there for calcium, liver for vitamin A and copper. Get the shares wrong in either direction and the stool tells you before anything else does.
- Feed the percentage of the dog you want, not the one you have Two to three percent of body weight is the standard rule, and it quietly maintains an overweight dog. The weight you use is the one that matters.
Everyday Life
4 guides- Why a pool can hold chlorine and algae at the same time Stabiliser protects chlorine from sunlight and slows it down at the same time. Once it climbs, the chlorine reading you trust stops meaning what it did.
- Shock is a level to reach, not a bag to tip in One bag per 10,000 gallons is a guess at a number that depends on your stabiliser. Fall short of breakpoint and you make the smell worse, not better.
- Dough temperature decides the timing, not the recipe Bulk times in recipes assume a kitchen you do not have. Temperature and how much starter you used move the clock by hours in either direction.
- The flour hiding in your starter A recipe at 70% hydration is usually not at 70%. The starter brings its own flour and water, and counting them moves the real figure by several points.