Energy Bill Estimator

How to use the energy bill estimator

Enter your monthly usage in kilowatt-hours and your supply rate, add the fixed monthly charge from your bill, and — under Advanced — any tax, and you get the total bill plus the genuinely useful part: the true all-in cost per kWh once everything is counted. The supply rate varies widely: the US residential average is about 17.5¢/kWh as of 2026, anywhere from roughly 10¢ to over 40¢ by state, so use the figure from your own bill.

The reason to care about the all-in rate is that the per-kWh “rate” utilities and plans advertise is only the energy charge. Your real cost per kWh is the whole bill divided by the kilowatt-hours you used, and it’s always higher because of fixed charges and tax. That all-in number is the honest one for comparing plans, judging a fixed-rate offer, or deciding whether an efficiency upgrade actually pays off.

Fixed charges are the part people forget. Most bills carry a fixed monthly service, connection, or customer charge — often $10 to $20 — that you pay no matter how little you use. It pushes your effective rate up at low usage and is the reason cutting consumption never drives the bill to zero. Pull the exact figure off your bill; it’s usually a clearly labeled line near the top.

Tax and other line items round it out. Many bills add a sales or utility tax, and some carry riders, surcharges, or delivery charges billed separately from supply. The Advanced tax field takes a percentage; if your bill has per-kWh delivery charges, the most accurate move is to fold them into the rate you enter, so the supply-plus-delivery total reflects what you’re really charged per unit.

Tiered and time-of-use plans need one adjustment. Some utilities bill in tiers (the rate steps up past a usage threshold) or by time of use (peak versus off-peak). This estimator uses a single flat rate, which is exactly right for most plans and a fair approximation for the rest. If you’re on a tiered or TOU plan, enter your blended average rate — the total energy charge divided by kWh — for the closest estimate.

The formula

The bill is the energy you used at your rate, plus the fixed charge, with tax applied to the whole subtotal. The all-in rate is just the total divided by your usage:

energy charge = kWh × rate
subtotal = energy charge + fixed charge
total = subtotal × (1 + tax%)
all-in rate = total ÷ kWh

Worked example with the defaults — 900 kWh at $0.175, a $15 fixed charge, 5% tax: energy is 900 × $0.175 = $157.50, plus $15 is $172.50, times 1.05 is $181.13. Divide by 900 kWh and the true all-in rate is $0.2013 — about 15% above the $0.175 headline.

The gap between the headline and all-in rate widens as usage falls, because the fixed charge spreads over fewer kilowatt-hours. At 300 kWh the same $15 charge alone adds 5¢ to every kWh; the less you use, the more each unit effectively costs you.

Frequently asked questions

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