Understand your bill
How billing days affect your electric bill
By the Energy Savings AI editorial desk · Edited by Carlos Gil, publisher · Updated November 1, 2026 · first published October 31, 2026 · Not yet technically reviewed
Key takeaways
- A longer billing period shows more kWh even when your habits don't change: a 34-day bill covers about 21% more days than a 28-day bill.
- Divide kWh by billing days to compare how much you used, and divide electric charges by days to compare what you paid per day.
- On tiered rates such as FPL's and JEA's, a long billing period can also push more kWh above 1,000 into the higher price.
Billing periods aren't all the same length, and the number of days changes your bill even when your habits don't. A 34-day bill covers about 21% more days than a 28-day bill, so at the same daily use it shows about 21% more kWh. To compare bills fairly, divide kWh by the number of days and compare kWh per day.
Why the number of days changes
Put two of your bills side by side and the service dates rarely line up to the same number of days. Those dates tell you exactly which days you were billed for. Count them, or use the "days" figure if your bill prints one.
The fix: compare per day
- kWh per day = kWh used ÷ billing days. This tells you whether your household actually used more.
- Cost per day = this period's electric charges ÷ billing days. This tells you whether the bill costs more per day, for any reason.
Illustrative example: same habits, $23.40 more
Invented numbers, one price of 13¢ per kWh and $15.00 of fixed charges on both bills. The household uses 30 kWh every day.
| Bill | Days | kWh | kWh per day | Per-kWh charges ($) | Total ($) |
|---|---|---|---|---|---|
| Shorter period | 28 | 840 | 30.0 | 109.20 | 124.20 |
| Longer period | 34 | 1,020 | 30.0 | 132.60 | 147.60 |
The second bill is $23.40 higher. All of it comes from the six extra days: $0.13 × 6 days × 30 kWh/day = $23.40. Daily use didn't change, so the "more kWh per day" part of the change is $0.00.
Our bill comparison splits the usage part of any change this way, into a billing-days part and a daily-use part. The two always add up to the usage change, so nothing is counted twice.
Where longer periods cost more than their share
If your utility charges more per kWh above a monthly threshold, a long billing period can push more kWh into the higher price. FPL's and JEA's residential rates both step up above 1,000 kWh in a billing period.
Illustrative example using FPL's October 2026 residential prices
A household uses a steady 32 kWh a day. FPL's per-kWh charges add up to 12.258¢ for the first 1,000 kWh and 14.258¢ above that, with a $10.52 base charge (before taxes and local fees). This assumes the 1,000 kWh threshold applies to each bill as printed on the rate sheet; check how your own bill applies it.
| Bill | kWh | kWh above 1,000 | Per-kWh charges ($) | With base charge ($) |
|---|---|---|---|---|
| 30 days | 960 | 0 | 117.68 | 128.20 |
| 34 days | 1,088 | 88 | 135.13 | 145.65 |
The 34-day bill is $17.45 higher. Most of that, $15.69, is the 128 extra kWh at the first-tier price (128 × 12.258¢). The other $1.76 is the higher tier: 88 kWh × 2.000¢ extra. Same habits, a slightly higher average price per kWh.
The same check on a JEA bill
JEA's residential rate also steps up above 1,000 kWh. Counting the energy charge and the November 2026 fuel charge, each kWh costs 12.79¢ up to 1,000 kWh and 14.68¢ above that, plus a $21.00 basic monthly charge (before taxes and fees). JEA resets its fuel rate every month, so compare the fuel line on both bills as well as the days.
Illustrative example using JEA's rates
A household uses a steady 30 kWh a day. A 35-day period is long, but it keeps the arithmetic easy to follow. Both bills are shown before taxes and fees, with the same basic monthly charge.
| Bill | kWh | kWh above 1,000 | Per-kWh charges ($) | With basic charge ($) |
|---|---|---|---|---|
| 30 days | 900 | 0 | 115.11 | 136.11 |
| 35 days | 1,050 | 50 | 135.24 | 156.24 |
The 35-day bill is $20.13 higher. The first 100 extra kWh cost 12.79¢ each, or $12.79. The last 50 fall above 1,000 kWh and cost 14.68¢ each, or $7.34. $12.79 + $7.34 = $20.13, and the household's daily use didn't change at all.
Fixed charges and longer periods
A fixed monthly charge may or may not be adjusted for a short or long billing period; it depends on the utility. Don't assume either way. Compare the fixed charge on both bills: if it's the same, the extra days only affected the per-kWh lines.
Comparing across seasons
kWh per day removes the calendar effect, not the weather effect. A July bill and an April bill can differ on a per-day basis simply because air conditioning runs more in a hot month. For a fairer test of whether something changed in your home, compare kWh per day with the same month last year. Many bills chart past months; JEA's, for example, shows 13 months of consumption history.
A step-by-step check for any two bills
- Write down the service dates and the number of days on each bill. If the bill prints a days figure, use it. If you count from the dates yourself, count the same way for both bills.
- Write down the kWh used and this period's electric charges on each bill, not the amount due.
- Divide both by the days to get kWh per day and cost per day.
- Compare the fixed monthly charge line on the two bills. If it's the same, the days only changed the per-kWh lines.
- On FPL or JEA, check whether either bill went past 1,000 kWh. Every kWh above that line costs more than the ones below it.
- Check the fuel line. JEA's fuel rate was $42.82 per 1,000 kWh in September 2026, $43.26 in October and $49.75 in November.
- If kWh per day went up, look for what changed at home: the weather, more people in the house, or new equipment.
The bill comparison does the per-day arithmetic for you and splits the change into usage, price and fixed charges, with the usage part divided into billing days and daily use.
Turning kWh per day into a monthly picture
kWh per day also makes budgeting easier. Multiply it by 30 for a standard month: 30 kWh a day is 900 kWh per 30 days. For a rough reference, EIA's 2024 average of 1,104 kWh a month for Florida residential customers is about 36.3 kWh a day averaged over the year (1,104 × 12 ÷ 365), and the US average of 863 kWh is about 28.4 kWh a day. Averages mix every kind of home, so treat them as a reference point, not a target.
The same arithmetic tells you what one more kWh a day is worth. Over 30 days it adds 30 kWh. At the price of the next kWh, before taxes and local fees, that is about $3.68 on FPL's October 2026 rate below 1,000 kWh (30 × 12.258¢) and $4.28 above it (30 × 14.258¢). On JEA's rates it is about $3.84 below 1,000 kWh (30 × 12.79¢) and $4.40 above it (30 × 14.68¢).
What to do with this
- Find the service dates and kWh on your two most recent bills, and divide.
- If kWh per day is flat but the bill rose, the change came from days, price or fixed charges. The bill comparison shows which.
- If kWh per day rose, start with the free bill check to see what's worth looking at in your home.
Frequently asked questions
Why are my electric billing periods different lengths?
Each bill covers the dates printed in its service period, and those rarely add up to the same number of days twice. Count the days between the service dates, or use the days figure if your bill prints one, before comparing two bills.
How do I compare two electric bills fairly?
Compare kWh per day (kWh used divided by billing days) to see whether your household used more, and cost per day (electric charges divided by days) to see whether the bill cost more per day. To remove the weather effect as well, compare with the same month last year.
How much does one extra billing day cost?
At steady use, one extra day costs your daily kWh times your price per kWh. In this guide's illustrative example, a household using 30 kWh a day at 13¢ per kWh pays $3.90 for each extra day, so six extra days add $23.40.
Can a longer billing period push me into a higher rate tier?
Yes. In this guide's illustrative example on FPL's October 2026 residential prices, a steady 32 kWh a day comes to 960 kWh over 30 days but 1,088 kWh over 34 days. The longer bill is $17.45 higher before taxes: $15.69 for the extra kWh at the first-tier price and $1.76 for the 88 kWh billed at the higher tier.
Is the fixed monthly charge prorated for a short or long bill?
It depends on the utility, so don't assume either way. Compare the fixed charge on both bills: if it is the same, the extra or missing days only affected the per-kWh lines.
Sources
- FPL residential rates, October 2026 (PDF) · checked October 31, 2026
- JEA rates (electric rates, fuel rate history, taxes and fees) · checked October 31, 2026
- JEA, Bill explanation · checked October 31, 2026
- U.S. Energy Information Administration, Electric Sales, Revenue, and Average Price, Table 5.a (2024 data) · checked October 31, 2026