Why You Need a Rate Calculator
Nobody Knows What They Pay for Electricity
Ask any homeowner what they pay per kilowatt-hour and you’ll get a blank stare or a single number that’s wrong.
That single number — the “average rate” — hides a stack of charges that vary by utility, by season, by time of day, and by how much you use. Your actual cost per kWh is a formula, not a number. And that formula is buried in regulatory filings that were never designed for humans to read.
This matters because every solar decision starts with “how much am I paying for grid power?” Get that wrong and your payback estimates, battery sizing, and time-of-use strategy are all built on sand.
What’s Actually on Your Bill
A residential electricity bill isn’t one price. It’s a stack of independently regulated charges multiplied together. A typical Oregon PGE bill includes:
Per-kWh charges (vary by tier and time of day): generation, transmission, distribution, power cost adjustment, regulatory items, state passthrough, and program charges.
Fixed monthly charges: basic charge (the fee for having a meter) and schedule adjustments.
Taxes: county privilege tax and city franchise fee.
The all-in effective rate for a single tier:
effective_rate = (usage + transmission + distribution + PCA
+ regulatory + state_passthrough + programs)
× (1 + combined_tax_rate)For a time-of-use plan, you have different rates for off-peak, mid-peak, and on-peak — each with its own component charges. A single bill might produce 3 different effective rates depending on when you used the power.
Why Can’t You Just Look This Up?
You’d think someone would have a clean database of residential electricity rates. They don’t.
No standardized format. Every utility names and structures its tariffs differently. PGE calls it “Schedule 7.” Pacific Power calls it “Schedule 4.” There is no national standard.
Thousands of distinct tariffs. Roughly 3,000 electric utilities in the US, many with multiple rate schedules. The total number of distinct residential tariffs is in the tens of thousands — and they change every year.
Deregulated states add chaos. In 14 states, customers choose their supplier. That means dozens of competing offers per location with different structures and promotional rates.
Tariffs live in PDFs. Utilities “publish” tariffs by uploading PDF scans of regulatory filings. Formats vary wildly. Most aren’t machine-readable.
Public data is too shallow. The best nationwide data (federal EIA filings) only reports average revenue per kWh — one number from total sales divided by total revenue. It tells you nothing about tier structure, fixed vs. volumetric split, or individual charges.
| Data level | Publicly available? | Useful for calculating your rate? |
|---|---|---|
| National averages | Yes | No |
| State averages | Yes | No |
| Utility averages | Yes | No |
| Full tariff structures | Partial, fragmented | Yes, but hard to get |
| Nationwide structured tariff DB | Doesn’t exist | — |
What This Means for Solar
If you’re sizing a system, evaluating payback, or running real-time energy tracking, you need your actual rate, not an average.
- Payback calculation needs the all-in effective rate including every adder and tax
- TOU optimization needs exact time-of-day rate boundaries for load shifting and battery sizing
- Home Assistant energy tracking needs per-tier effective rates to compute real-time costs
What the Rate Calculator Does
Since no public database gives you what you need, the Rate Calculator works backwards from your actual bill:
- Extract — Upload your bill (photo, PDF, or enter manually). AI or your eyeballs pull every line item.
- Decompose — The formula engine separates volumetric from fixed charges, identifies per-tier components, and computes the all-in effective rate for each tier.
- Validate — Enter your actual bill total and usage. If the estimate matches, the rates are right.
- Export — Copy validated rates into the Solarseed Home Assistant plugin for real-time cost tracking.
The result: instead of guessing “about 15 cents,” you know your off-peak rate is $0.1598/kWh, mid-peak is $0.2087/kWh, and on-peak is $0.2682/kWh — validated against your actual bill to within 1%.
Ready? Open the Rate Calculator →