Do I have a demand charge?
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What a demand charge is
Most of your bill is kilowatt-hours (kWh): how much energy you used. A demand charge is different. It's a price per kilowatt (kW) for the most power you drew at once.
Your utility averages your power over a 15-, 30- or 60-minute window. It finds the highest average that happened during the plan's peak hours. Then it multiplies that number by a $/kW rate. That one number sets the charge for the whole month.
So one bad half hour counts. Run the AC, the dryer and an EV charger together at 6 PM and you might set a 10 kW peak. At a made-up rate of $15 per kW, that half hour adds $150 to the bill, even if the rest of the month was quiet.
For a longer walk-through with real numbers, read demand charges explained.
How to spot one on your bill
A line in kW, not kWh
Energy charges are in kWh. A demand charge is in kW. The line may say demand, on-peak demand, maximum demand or billing demand.
A dollar amount per kW
You'll see a number of kW, a rate like $12.50 per kW, and the two multiplied into a charge.
It hits harder with EVs, AC and solar
EV charging, AC and electric dryers
A Level 2 EV charger can pull 7 to 11 kW on its own. Add central AC and a dryer in the same half hour and your peak jumps. These set the number more than anything else in the house. More on the appliances that set your peak and EV charging with a Powerwall.
Solar often fades before the peak ends
Many plans put peak hours in the late afternoon and evening, when solar output is falling. A battery can cover that window if it's charged and set to discharge then. That's why people with solar plus a battery watch their demand charge.
Have one? See what it could cost you each month. If you have a Tesla Powerwall and a demand charge, DemandGuard works to keep your peak down. Or get the free report for Tesla Powerwall owners to see your own biggest peak.
About demand charges
What is a demand charge?
A demand charge bills you in dollars per kilowatt (kW) for your highest burst of power use in a month. Your utility averages your power over a 15-, 30- or 60-minute window, finds the highest average inside the peak hours, and charges that kW number times a rate. It's on top of what you pay for the energy itself.
How do I know if I have a demand charge?
Look at your bill for a line measured in kW, not kWh. It might be called demand, on-peak demand, maximum demand or billing demand. If your charges are all in kWh, you most likely don't have one. If you're not sure, type your ZIP code above to see which plans in your area have one.
What's the difference between kW and kWh?
A kWh is an amount of energy, like gallons of gas. A kW is how fast you're using power at one moment, like miles per hour. Demand charges use kW, so one short spike can set the price for the whole month.
Why does a demand charge matter more with EV charging, AC or solar and a battery?
Big loads set the peak. An EV charger, central AC and an electric dryer running together can push you well above your normal use for half an hour. Solar alone doesn't help much, because the sun is often fading by the evening peak. A battery can cover that window, but only if it has charge and is set to discharge at the right time.
Does my demand charge apply every day?
It depends on the plan. Many only count peak hours, such as weekday afternoons and evenings, and some only in summer. Most bill one number for the month, so a single bad half hour can cost you for the whole billing period. A few plans average each day's peak instead.
Can the checker be wrong?
Yes. It matches your ZIP code to the plans on file for that area, and more than one utility can serve a ZIP. Plans change and some records are out of date. Your bill is the final word, so treat the result as a starting point.