About the Tiered Electricity Rate Calculator
This tiered electricity rate calculator works out an electric bill when the price per kWh changes with how much you use. Under a tiered (also called inclining block or stepped) rate, the first block of kWh each month is billed at a low price, the next block at a higher price and anything above that at the highest price. Enter your usage, the tier limits and prices from your utility’s rate schedule, the fixed monthly customer charge, any per-kWh riders and the tax rate.
It is useful for checking a bill, budgeting for a summer of air conditioning, or seeing what an EV charger or a new heat pump will really add. The marginal rate — what your next kWh costs including riders and tax — is often much higher than the average rate, and it is the number that matters when you decide whether a new appliance or a solar system is worth it.
Tier 2 and tier 3 limits are entered as cumulative kWh: if tier 1 covers the first 500 kWh and tier 2 runs to 1,000 kWh, tier 3 starts at kWh 1,001. Some utilities set the tier 1 allowance by season, climate zone or days in the billing cycle, so copy the allowance printed on your bill. For declining block rates, simply enter lower prices for the higher tiers.
With the default inputs, the total monthly bill is $164.85. Change any value above to recalculate instantly.
How to use the tiered electricity rate calculator
- 1Enter the kWh used in the billing period.
- 2Copy the tier limits and prices from your utility’s rate schedule or bill.
- 3Add the fixed customer charge and any per-kWh riders.
- 4Enter the combined tax and surcharge percentage.
- 5Review the total, the per-tier breakdown and your marginal price per kWh.
Formula and method
Usage fills the tiers in order: up to L₁ kWh at the tier 1 price, the kWh between L₁ and L₂ at the tier 2 price, and everything above L₂ at the tier 3 price. Per-kWh riders such as delivery, fuel adjustment or renewable surcharges apply to every kWh. The fixed customer charge is added, and taxes are applied as a percentage of the whole subtotal.
The average price is the total bill divided by kWh used. The marginal price is the tier price that applies to the next kWh plus riders, grossed up for tax — the right figure for estimating the cost of extra usage or the value of savings. Some utilities tax fixed charges differently or apply minimum bills; check your tariff if the result differs slightly from your bill.
- L₁, L₂
- Cumulative kWh limits where tier 1 and tier 2 end
- R₁, R₂, R₃
- Energy price in each tier ($/kWh)
- r
- Other charges applied per kWh
Worked examples
900 kWh across two tiers
The first 500 kWh cost 500 × $0.12 = $60 and the next 400 kWh cost 400 × $0.15 = $60. Adding $27 of riders and the $10 fixed charge gives $157, and 5% tax brings the bill to $164.85 — an average of $0.183 per kWh, while the next kWh costs $0.189.
Summer month reaching tier 3
At 1,500 kWh, 500 kWh fall in each tier: $60 + $75 + $95 = $230 of energy. With $45 of riders, the $10 fixed charge and 5% tax the bill is $299.25. Each extra kWh now costs $0.231, so trimming air-conditioning use saves more than the average rate suggests.
Small apartment, no tax
All 350 kWh fall in tier 1, so energy costs 350 × $0.12 = $42. With $10.50 of riders and a $12.50 fixed charge the bill is $65, an average of $0.186 per kWh because the fixed charge is spread over fewer kWh.
Frequently asked questions
What is a tiered electricity rate?+
A tiered or inclining block rate charges a lower price for a baseline amount of electricity each month and higher prices for usage above it. It is designed to make essential use affordable and encourage conservation. Many US utilities, including several in California, use tiers or baseline allowances.
How do I find my tier limits?+
Your bill or your utility’s published rate schedule (tariff) lists the kWh in each tier and the price per kWh. Some utilities set the first-tier allowance by season, climate zone, heating type or days in the billing period, so use the allowance printed on the specific bill you are checking.
Why is my average rate higher than my tier 1 price?+
The average includes the fixed customer charge, per-kWh riders and taxes on top of the energy price, and any usage in higher tiers. A fixed charge has the biggest effect on low-usage bills because it is spread over fewer kWh.
What is the marginal rate and why does it matter?+
The marginal rate is what one additional kWh costs you, including riders and tax, at your current usage. It is the right number for estimating what a new appliance, EV charging or a space heater will add, and what you save by cutting usage or adding solar.
Is a tiered rate or time-of-use rate cheaper?+
It depends on how much and when you use electricity. Low-usage homes often do well on tiered rates, while homes that can shift usage to off-peak hours, such as EV owners charging overnight, frequently save on time-of-use plans. Compare both using your actual usage.