How to Read Your Electric Bill for Solar (Before You Size a System)

Most solar quotes start with a single month of bills and a salesperson's gut feeling. That is a recipe for a system that is either too small or 30 percent too big. The fix is not a fancier calculator. It is spending thirty minutes on your own bill and pulling out the numbers that actually drive the math.

Your bill is the only true source for two things: how much electricity you really use, and what each unit costs once every charge is in. Here is how to read it correctly.

Get twelve months, not one

A single bill hides a lot. One month can capture a heat wave, an empty house, a rate change, a true-up, or a one-time credit. Pull twelve consecutive bills in their original PDF form. Add any annual true-up statement and the current utility solar rider if you have one.

Then do two things. Sum the billed kilowatt-hours across all twelve months to get your real annual consumption. Do not average one number and round it. And keep your taxes, credits, late fees, and prior balances in separate columns so they do not dress up your energy price.

The average US home uses roughly 875 kWh per month, or about 10,500 kWh a year. But your number, not the average, is what a system is sized against.

Find your rate schedule code

Near the top of the bill, there is a code. It might be called your Service Plan, Rate Plan, or Schedule. Examples: PG&E uses E-1 or E-TOU-C. Southern California Edison uses TOU-D-PRIME. ConEd in New York uses SC1 Rate 2. Duke uses Schedule RS or Schedule R-TOUE.

That code is a contract identifier. Look it up on your utility's tariff page and you will find the official per-kWh price, the definition of peak hours, any fixed charge, and any minimum bill. A single "average" number on the bill often hides the fact that the price changes by time of day or by tier.

This one line decides whether your midday solar is worth full retail price or a fraction of it. If you are on a time-of-use plan, the export rate can discount midday production by 30 to 70 percent, and that reshapes your whole payback.

The trap: the all-in average rate

Here is the mistake that quietly inflates savings. If you divide your total bill dollars by your total kWh, you get a number like 20 cents per kWh. That sounds like your electricity price. It is not, at least not the part solar can remove.

That all-in average includes your fixed customer charge, taxes, prior-period adjustments, and other amounts that solar does not avoid. You will still pay the fixed monthly fee no matter how big your array is.

Worked example from a real bill pattern. Twelve bills totaling 2,400 dollars on 12,000 kWh, with an 18 dollar monthly customer charge. The all-in average is 20 cents per kWh. Strip out the 216 dollars of fixed charges and you get 18.2 cents per kWh as your real avoidable rate. Multiply a proposed 10,000 kWh of production by 20 cents and you will report 2,000 dollars of savings. Count only what solar actually avoids and you get about 1,028 dollars. The difference is the gap between an honest estimate and a number built on a fixed charge you were going to pay anyway.

The US average residential rate is about 18.3 to 18.4 cents per kWh, up from 15 cents four years ago. It ranges from the low 13 cents in Nevada to the high 50 cents in Hawaii. Your avoidable rate, pulled from your own bill and tariff, is the number to use. Not the national average.

The four numbers that matter

From all of that, you only need four things to size and value a system:

1. Your annual billed kWh (sum of twelve months).
2. Your rate schedule code and the import price for each period.
3. Your fixed and non-bypassable charges per year.
4. Your monthly shape, the high and low months, not just the total.

That fourth one is the one installers skip. A home that peaks in the summer and another that peaks in the winter have the same annual total but very different solar fit. Compare the seller's monthly production against your monthly load, not just the yearly number.

What to do with it

Take those four numbers and any installer quote should be able to rebuild its savings figure from them, plus the utility tariff and a roof-specific production report. If a proposal's annual savings cannot be traced back to your own twelve-month bills and your actual tariff, that is a red flag.

Your bill tells you what your home needs. But it cannot tell you what your roof can fit, how much shade is actually hitting it, or your exact annual sunshine hours. Those are the numbers that decide whether the math on paper becomes a system you can actually build.

At SolrScan, a 19 dollar satellite scan of your home gives you your exact sunshine hours, the number of panels and wattage that fit your roof, your system size and install cost, and your projected savings in minutes, with no appointment and no pitch. Run it at https://solrscan.com and see what your home can actually do before you commit to a quote.