How much does solar cut your power bill?
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Run hour by hour, with net metering (Puerto Rico, Act 114-2007) · 2026-10-18
A house with one A/C at night pays about $126 a month to the utility. With 14 panels it pays $8 — and that is the fixed service charge, not a saving: you pay it whether you use a single watt or not. The bill does not reach zero. It gets there in a month of typical days and in a month of overcast ones alike, which is what makes the number worth quoting.
Nobody can honestly give you one percentage, and this page will not either: what your bill does depends on the weather of your month. So every cell below is a range between a month of typical days and a month of overcast ones — a month better than typical lands below the low figure. Where the two figures meet, the system covers the house whatever the sky does.
Sources reviewed ·
Before comparing a solar offer
Your bill can rise without using more
In Puerto Rico, for October–December 2026, PREB’s unsubsidized residential example at 800 kWh rises from $228.59 to $270.86 a month: $42.27 more. Your increase depends on your usage and rate. The $8 fixed charge is already included in this example.
Read the NEPR order, Annex 4 (PDF, Spanish). These are quarterly reference figures, not a guaranteed future rate.
Compare everything you would pay. Add the solar payment to the remaining utility bill. A lower utility bill alone does not establish savings.
Check financing, incentives and battery sharing
Financing is a loan
EcoHogar, from PRGET and Cooperativa Jesús Obrero, lists solar-plus-battery loans up to $75,000, from 5.95% APR, for up to 15 years. Approval, the final rate and availability must be confirmed with the lender. An energy assessment and an approved contractor are required.
Read official requirements (English). This is an external resource; it does not establish a commercial relationship with Adiós Factura. Our simulator does not replace the required assessment.
Do not automatically deduct a 30% tax credit
The IRS states that the homeowner’s residential 25D credit does not apply to installations completed after December 31, 2025, even if paid for earlier. This does not determine the tax treatment of every commercial project. IRS guidance, question 7.
Sharing battery energy changes your reserve
Puerto Rico’s CBES program works through aggregators. Confirm equipment eligibility, your compensation and the backup reserve before enrolling. A fully off-grid system cannot export to the utility. Our savings estimates do not add income from this program. Read program details.
The bill, by house and by system size
Monthly bill at 0.328575 $/kWh — a variable rate derived from the NEPR residential reference bill for October–December 2026, excluding the fixed charge — with the surplus swapped one for one against what you buy back, which is what the law allows.
| The house | No solar | 8 panels | 14 panels | 20 panels |
|---|---|---|---|---|
| The essentials 198 kWh a month |
$73 | $8 | $8 | $8 |
| With one A/C at night 309–360 kWh a month |
$109–$126 | $8–$46 | $8 | $8 |
| How people actually live 759–984 kWh a month |
$257–$331 | $120–$192 | $8–$144 | $8–$97 |
Why the bill does not go to zero
Two reasons, and both are arithmetic, not fine print.
The fixed charge. $8 a month for being connected. Even the largest system on this table leaves a bill of $8, and every cent of that is the meter itself.
The night. Panels produce during the day and the house spends at night. Under net metering the surplus you send in the afternoon is credited against what you draw after dark, one kWh for one kWh — but only up to what you buy back. Beyond that it becomes carried credit, and carried credit is not money.
What happens to the surplus
In Puerto Rico: it carries month to month until the June closing. What is left then is paid at ten cents per kWh, or the rate minus the fuel (FCA) and purchased-power (PPCA) adjustments — whichever is greater — and 25 % of it goes to the public schools, which is in the law and worth knowing before you oversize on purpose.
Which is the honest argument against building a system far bigger than the house: past the point where the surplus stops being swapped, every extra panel is paid at a fraction of the rate.
A real bill, month by month
Historical example, August 2025–August 2026. These amounts retain their original dates and rates.
Six real bills from the utility (Puerto Rico) for one net-metered house in Caguas — the same town the three houses above are run in — read line by line. No name, no account number: the mechanics are what matter, and they are the same for anyone with panels and a two-way meter.
| Period | Bought (kWh) | Exported | Swapped | Banked at close | Charges |
|---|---|---|---|---|---|
| Aug–Sep 2025 | 535 | 743 | 535 | 208 | $4.00 |
| Mar–Apr 2026 | 527 | 744 | 527 | 874 | $4.00 |
| Apr–May 2026 | 854 | 581 | 854 | 601 | $4.00 |
| May–Jun 2026 | 863 | 614 | 863 | 352 | $4.00 |
| Jun–Jul 2026 | 956 | 520 | 520 | 0 * | $128.22 |
| Jul–Aug 2026 | 1,030 | 527 | 527 | 0 | $146.70 |
* The closing: the 352 kWh banked in May were cashed out on the next bill as «Net metering credit — fiscal year: −$26.40», and the bank restarted at zero.
What the 0.2757 $/kWh is made of. The bill charges the kWh you buy in six lines, and every one of them is per kWh:
- Energy charge: 8.648 ¢
- FCA — fuel adjustment: 11.407 ¢
- PPCA — purchased power: 5.175 ¢
- CILTA — payment in lieu of taxes: 0.739 ¢
- Subsidies (HH and NHH): 1.52 ¢
- EE — energy efficiency: 0.085 ¢
27.6 ¢ in all (August 2026) — and the net metering credit line hands back exactly that sum for every kWh swapped, which is why, while the bank holds, the bill is the customer charge and nothing else: $4 then, $8 since July 2026. That is the $4.00 you see in the first four rows.
What the bank does, and what June does to it. The credit carries from month to month (208 → … → 874 → 601 → 352 kWh). At the closing it is cashed out: this house reached it with 352 kWh and the next bill shows «Net metering credit — fiscal year: −$26.40». That is 7.5 ¢ per kWh — 4 times less than the kWh costs to buy — and the 25 % the law sends to public schools is already out of it.
And June is right before summer. The bank builds from November to May, with little A/C, and is cashed out the month before A/C drives purchases up. Same house: 956 and 1,030 kWh bought in July and August against 520 and 527 exported — $128.22 and $146.70. Had the 352 kWh still been there at full rate, those two months would have cost about $97 less. Size for July and August, not for the yearly average; the simulator's «with the grid» card says the same in numbers.
And that house does not own its panels
The system belongs to a PPA company, under a 25-year contract from April 2025: «we own the system and provide you its electricity». It produces about 11,465 kWh a year and comes with a battery. The customer pays 10 ¢ for every kWh the system produces — on the estimated production, fixed, «the same every month even if it produces more than expected» — plus $130 a month for battery service: $225.54 a month, with a 0 % escalator and $0 down. And the power bill above, on top.
Add it up: $2,706 a year to the company, plus the utility — $4 most of the year and $128.22 and $146.70 in July and August — over $3,000 a year, and $372.24 in the worst month. Before the panels, in April and May 2025, that house bought 950 and 840 kWh: at the August 2026 reference rate, $240 to $270 a month. In 25 years it will have paid $67,662 on the contract and the system will still not be theirs; the battery alone, at $130 a month, comes to $39,000.
And the sum a per-kWh PPA does not do for you: every kWh you export that reaches the June closing costs you 10 ¢ and the utility buys it for 7.5 ¢. In March–April that house exported 744 kWh.
The whole first year, off the two meter registers. The two-way meter started at zero on the day of the install, and the August 2026 bill carries both readings: 7,871 kWh bought and 7,284 kWh exported in twelve months. If the system produced what the contract estimates, the house used about 12,052 kWh. With no panels, at the August 2026 reference rate: about $3,419 a year, $285 a month. With the PPA plus what the utility actually billed: about $3,021 a year, $252 a month. The saving is about $397 a year — $33 a month — for a 25-year contract on a system that will never be theirs. The 0 % escalator is the one thing in their favor: if the rate keeps rising, the saving grows; the summer bill rises with it.
The figures are from the contract and the bills; neither the person's name nor the company's: what matters is not who, but what one signs. The page on making the system yours — loan, PPA or lease, what is left to you at the end — is in Spanish.
Work out your own bill, hour by hour →
Free, no card and no sign-up. Your appliances one by one, your town's sun, and what is left to pay.
Rate reference: 0.328575 $/kWh, derived from the NEPR example of $270.86 at 800 kWh for October–December 2026, with the fixed charge removed. NEPR order, September 30, 2026, Annex 4 (PDF, Spanish). Fixed charge $8 a month since July 2026 (it was $4 before). Net metering under Act 114-2007, art. 5(e), with the June closing — protected until at least 2030 by Act 10-2024. Consumption and production come from running the same hour-by-hour engine as the simulator, in the central valley, on a 17° roof facing south. Your bill will differ with the quarterly adjustments, your roof and what you actually leave running.