Is Solar Worth It? Calculating ROI When Export Credits Are Lower Than Retail
Rising grid rates, FPA/QTA/GST, and evening ToU peak charges push households toward rooftop solar. Payback still depends on how much you self-consume during the day versus how much you export under current net metering or net billing rules. This independent guide walks through the cashflow logic — verify contract terms with official DISCO/NEPRA documents, not marketing flyers alone.
Not affiliated with MEPCO, PITC, WAPDA, or NEPRA. Hardware prices, export credits, and interconnection rules change — treat every number here as planning context, not a quote.
Prerequisites before you size a system
12 months of units
From official bills via official PITC portal ↗ — daytime vs evening pattern matters.
Roof & load reality
Shade, orientation, and which loads can run while panels generate.
Signed rules
Read the interconnection / net metering or net billing terms that apply to your application date.
The ROI framework in one sentence
Annual benefit ≈ (daytime kWh you no longer buy from the grid × avoided retail-like cost including typical adjustments/taxes) + (exported kWh × export credit rate) − O&M. Divide system cost by annual benefit for a rough payback. Oversizing for export when the credit is low lengthens payback. Use your signed credit rate and current bill — not a fixed “guaranteed” payback year from a brochure.
Net metering vs net billing (confirm your agreement)
Older net metering arrangements often netted units more generously. Newer frameworks may credit exports at a lower rate than you pay for imports (net billing-style settlement). Grandfathering can apply to existing licenses for a defined period. Always read your interconnection agreement and the latest NEPRA consumer rules — do not assume 1:1 forever.
Self-use vs export (decision table)
| Scenario | Usually better when… | Watch out for… |
|---|---|---|
| Daytime self-use | Export credit is below retail; you can shift loads into sun hours | Evening ToU peak still imports from the grid |
| Export-heavy sizing | Your signed agreement still values surplus highly | Weak export credit → long payback |
| Hybrid + storage | Peak imports and outages are costly relative to battery price | Higher upfront cost; model as a separate scenario |
Step 1: Maximize daytime self-consumption
- Shift flexible loads (washing, ironing, water pumping, EV/UPS charging if any) into sunny hours.
- Run ACs in occupied rooms while panels generate, within comfort needs.
- Avoid designing a system whose main profit story is “selling to the grid” if export credit is weak.
Step 2: Plan for ToU evening peak
Solar output collapses after sunset — exactly when many homes hit ToU peak. ToU peak windows vary by season and tariff; confirm on your bill or NEPRA schedule. Without batteries, evening grid imports still bill at peak rates. See the peak hours guide and, if you need runtime maths, the UPS backup calculator.
Step 3: Use realistic cost bands (not quotes)
Turnkey prices move with panel, inverter, and structure markets. Treat published ranges as planning anchors, then get written quotes from installers. Mid-size residential on-grid systems commonly fall in a wide band that can shift within months — verify locally rather than locking a rupee figure from this page.
Step 4: Worked payback sketch (illustrative only)
Suppose a mid-size residential system yields several thousand units per year on a decent South Punjab roof, with a majority self-consumed and the rest exported. Self-consumed units avoid a high effective retail cost; exported units earn only the credit rate in your agreement. Even with modest export earnings, avoiding retail-priced daytime units can still produce multi-year paybacks for many households — but your numbers will differ with yield, self-use share, tariffs, and O&M. Model yours with the solar system sizer, then stress-test against your official bills.
Step 5: When hybrid storage helps
Lithium storage adds upfront cost but can cover evening peak and load-shedding. It makes sense when peak imports and outage pain are large relative to battery price. Recalculate ROI with storage as a separate scenario, not an automatic add-on.
Step 6: Operations that protect ROI
- Wash panels frequently in dusty seasons — soiling can cut yield sharply.
- Keep string/inverter monitoring honest; a failed string silently destroys payback.
- After install, compare import/export on the official bi-directional bill via the official PITC portal.
What can go wrong
- Oversizing for export under a weak credit rate.
- Ignoring evening ToU peak AC load with no storage plan.
- Treating a marketing “payback in X years” as a guarantee.
- Skipping soiling / string failure monitoring after install.
- Assuming MEPCODBill processes net metering applications — we do not.
Next action: compare before/after on the official bill
We do not host your solar or grid bill PDF. Open the official PITC copy, and sanity-check sizing with the solar calculator.
Frequently asked questions
Should I oversize to export more?
Usually no when export credit is far below retail. Size closer to daytime self-use unless your signed agreement still makes surplus valuable.
Do existing net metering customers keep old terms?
Many are grandfathered for a defined period under their license — check your documents and NEPRA/DISCO notices rather than assuming.
Does MEPCODBill process net metering applications?
No. We are an independent guide and calculator site. Applications go through official DISCO / ENC / net metering channels.
Author note: Educational ROI logic only. Confirm interconnection, metering mode, and tariffs with official sources before investing.
Sources & verification
Official sources sit above third-party summaries. Open these pages to confirm the current figure or process.
- NEPRA Tariff SchedulesRetail and ToU rates that drive self-consumption value; net metering/billing rules change via NEPRA determinations
- PITC Bill PortalBaseline monthly units and charges before you model solar savings
- Solar CalculatorSizing / payback estimator — not a bankable quote or official interconnection study
- UPS Backup CalculatorEvening / outage runtime planning when solar alone does not cover peak