Water Heater

{
  "asOf": "2026-10-11T14:31:37.225Z",
  "costPerTankHeating": 1.397,
  "degraded": false,
  "disclaimer": "Screening signal computed from the named public source. Not financial, legal or investment advice; provided as is. Verify at the source before acting.",
  "efficiency": 0.98,
  "energyToHeatTankBtu": 29190,
  "energyToHeatTankKwh": 8.73,
  "formula": "recovery = input BTU/h x efficiency / (8.34 lb/gal x rise F)",
  "fuel": "electric",
  "heatUpHours": 1.94,
  "heatUpMinutes": 116,
  "inputBtuPerHour": 15355,
  "notChecked": [
    "standby (tank) losses, which keep costing energy all day and are not in the heat-up figure",
    "heat-pump water heaters, whose efficiency is 2 to 4 times higher than the resistance figure entered here",
    "…2 more"
  ],
  "reasons": [
    "Water weighs 8.34 lb per gallon and takes 1 BTU per lb per F, so a gallon needs 8.34 BTU per degree of rise.",
    "1 kWh = 3,412 BTU; 1 therm = 100,000 BTU."
  ],
  "recoveryGallonsPerHour": 25.78,
  "recoveryLitresPerHour": 97.6,
  "riseF": 70,
  "source": "computed locally",
  "summary": "4.5 kW at 98% efficiency and a 70 F rise recovers about 25.8 gallons per hour. Heating a cold 50-gallon tank takes about 1.9 hours. Each full heating costs about 1.397.",
  "tankGallons": 50,
  "verdict": "COMPUTED"
}

# bash or zsh: see the payment challenge. Nothing is charged.
curl -sS -g -i 'https://home-energy-calc.x402tookit.com/water-heater?fuel=electric&inputPower=4.5&pricePerKwh=0.16&riseF=70&tankGallons=50'

# x402 v2 sends the challenge base64-encoded in the PAYMENT-REQUIRED header (v1 sends it in the body).
# To read the header:
curl -sS -g -o /dev/null -D - 'https://home-energy-calc.x402tookit.com/water-heater?fuel=electric&inputPower=4.5&pricePerKwh=0.16&riseF=70&tankGallons=50' \
  | grep -i '^payment-required:' | cut -d' ' -f2 | tr -d '\r' | base64 --decode

// npm i @x402/fetch @x402/evm viem
import { wrapFetchWithPayment, x402Client } from "@x402/fetch";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

// Pays at most $0.02 per call.
const client = new x402Client().setSpendControls({ maxAmountPerPayment: "$0.02" });
registerExactEvmScheme(client, { signer: privateKeyToAccount(process.env.EVM_PRIVATE_KEY) });
const pay = wrapFetchWithPayment(fetch, client);

// Not sure it's safe to pay? ToolVet checks it first for $0.005. Pay for that from a separate
// client: this one is capped at $0.02 per payment. GET https://toolvet.app/api/v1/check?url=https%3A%2F%2Fhome-energy-calc.x402tookit.com%2Fwater-heater
const res = await pay("https://home-energy-calc.x402tookit.com/water-heater?fuel=electric&inputPower=4.5&pricePerKwh=0.16&riseF=70&tankGallons=50");
console.log(res.status, await res.text());

# pip install "x402[requests,evm]"
import os
from eth_account import Account
from x402 import x402ClientSync
from x402.http.clients import x402_requests
from x402.mechanisms.evm import EthAccountSigner
from x402.mechanisms.evm.exact.register import register_exact_evm_client

# Pays at most $0.02 per call.
client = x402ClientSync().set_spend_controls({"max_amount_per_payment": "$0.02"})
register_exact_evm_client(client, EthAccountSigner(Account.from_key(os.environ["EVM_PRIVATE_KEY"])))

with x402_requests(client) as session:
    res = session.get("https://home-energy-calc.x402tookit.com/water-heater?fuel=electric&inputPower=4.5&pricePerKwh=0.16&riseF=70&tankGallons=50")
    print(res.status_code, res.text)