Readiness checks before you sit down to review practice cases: (1) Given any utility bill, you can classify the rate structure in under two minutes and state what exported kWh are worth. (2) Given an irradiance figure and a site description, you can produce a specific-yield estimate with every derate assumption written down. (3) Given a customer goal, you can name the matching financial metric and explain what it hides. (4) Given a financing arrangement, you can build a year-by-year net cash flow, not just a payback figure. (5) You can write a three-sentence customer explanation of any proposal number without jargon. Treat scores from self-graded exercises as learning milestones, not predictions of your exam result.
What the PVTS actually asks you to produce: a defensible proposal
The PVTS credential rewards one repeated act: turning raw site, usage, and rate data into a proposal a customer can act on. Study every topic by asking which sales decision it feeds.
NABCEP lists PV Technical Sales as its own Board Certification, separate from installation credentials, with distinct eligibility, experience documentation, training, and recertification requirements described in its Certification Handbook. Notably, the handbook describes documenting experience through proposal documentation, which tells you the credential is anchored in real sales artifacts rather than installation skills.
Build your study plan around that anchor. For each technical domain, write the customer-facing sentence it supports: shading analysis supports a production promise; rate analysis supports a savings promise; incentive knowledge supports a net-cost promise. If a concept cannot be connected to a sentence in a proposal, you are studying installer material, and your review time is better spent elsewhere.
Reading a utility bill: tiered, time-of-use, and net-metered rates
Before any production math, classify the rate. Tiered rates make offset order decisive, time-of-use rates reward afternoon output, and the net-metering or export-credit rule decides what exported energy is actually worth.
Practice decoding a bill into its components: total consumption in kWh, the rate structure (flat, tiered, or time-of-use), fixed monthly charges, and any demand charges. Fixed charges matter because they dilute percentage savings: a customer with a large fixed charge sees a smaller bill reduction than raw kWh math suggests. Demand-charge customers, often commercial, need a different framing entirely, since shaving peaks can be worth more than offsetting volume.
Then trace how the structure changes your sizing logic. Under an inclining tiered rate, the first solar kilowatt-hours displace the customer's most expensive, top-tier energy, and marginal savings fall as a growing system pushes down into progressively cheaper lower tiers. Under time-of-use, a midday-heavy array may export much of its output at a low or near-zero credit, while late-afternoon output offsets expensive peak periods. Write the export-credit rate on your worksheet before sizing anything; it is the number most shortcut calculations get wrong.
Production estimates you can defend: derate factors and specific yield
A defensible estimate separates resource (irradiance), hardware losses (derate factors), and site losses (shading and orientation). Express results as specific yield so the magnitude can be sanity-checked at a glance.
Learn the loss chain by name: irradiance at the site, temperature losses, soiling, inverter efficiency, mismatch, and wiring losses. In a simplified worksheet, multiply the derate factors into a single performance ratio, then apply it to the plane-of-array irradiance. Treat shading with suspicion: a chimney or vent that shades one module for part of the day has an outsized effect on a string, so a worst-case module analysis is the defensible approach rather than averaging shade evenly across the roof.
Convert the result to specific yield, in kWh produced per kW installed per year, because it is the easiest number to sanity-check. Most fixed-tilt United States sites fall roughly between 1,000 and 1,600 kWh/kW-yr; a worksheet landing far outside that band signals an input error, not an exceptional roof. In a proposal, list every assumption next to the estimate. An estimate with visible assumptions is a professional commitment; an unexplained number is a liability.
Choosing the financial metric that matches the customer's decision
Simple payback, annual cash flow, net present value, and internal rate of return answer different questions. Match the metric to the customer: cash-flow-sensitive buyers need yearly net, comparison shoppers need returns.
Define each metric precisely. Simple payback is net investment divided by annual savings and assumes the customer paid cash up front. Annual net cash flow subtracts every ongoing cost, including loan payments, from savings, which is what a financed customer actually feels monthly. Net present value discounts future savings to today's dollars, and internal rate of return expresses the investment's yield as a percentage, useful when comparing solar against other uses of capital.
The trap is conflating them. A payback figure computed with loan-financed savings but without loan payments can look attractive while the customer's first years are net negative, which erodes trust when the first bills arrive. Practice writing all four metrics for one example, then decide which single number belongs in the executive summary for a given customer profile.
| Metric | Question it answers | Best matched to | What it can hide |
|---|---|---|---|
| Simple payback | How fast does the outlay return? | Cash purchasers | Time value of money; ongoing costs |
| Annual net cash flow | Does each year cost or save money? | Financed buyers | Long-run total value |
| Net present value | What is the deal worth in today's dollars? | Long-horizon comparisons | Intuitive feel; needs discount-rate assumptions |
| Internal rate of return | What yield does the capital earn? | Investment-minded buyers | Scale of the investment |
| Lifetime savings | How much over the whole period? | Value-focused customers | Incentive timing and uncertainty |
Worked scenario: sizing against a time-of-use rate
A plausible mistake is valuing every produced kWh at the blended average rate. A time-weighted calculation splits self-consumed from exported energy and values each correctly. Work the numbers yourself.
Scenario: a homeowner uses 10,800 kWh/yr on a time-of-use rate, $0.42/kWh during the 4–9 pm peak and $0.18/kWh off-peak, blending to about $0.28. Excess solar is exported and credited at $0.04/kWh. The shortcut estimate sizes a 7 kW system producing about 9,100 kWh/yr and values all of it at $0.28, promising roughly $2,548 in first-year savings. That number treats exported midday energy as if it were worth retail.
The better decision splits the output: suppose about 70% is self-consumed, much of it near the peak at an effective value near $0.31, and 30% is exported at $0.04. That yields about 6,370 × $0.31 plus 2,730 × $0.04, roughly $2,084. The gap is about eighteen percent, enough to overstate payback by years. It matters because the export-credit rate, not the array size, is the swing variable here, and a customer who later learns the real export value questions everything else in the proposal.
Worked scenario: quoting payback on a financed system
Payback math assumes cash up front. With financing, the honest picture is year-by-year net cash flow, separating savings from out-of-pocket cost. Run the comparison explicitly before choosing the headline number.
Scenario, with hypothetical figures for practice: a $25,000 system, a 30% credit applied (a placeholder; verify current incentives), netting $17,500, with annual savings of $2,200. The shortcut quotes simple payback of about eight years. But the customer finances the system at $2,900 per year in payments. In the early years the net cash flow is roughly negative $700 annually before any credit timing effects, which the payback sentence never mentions.
The better decision builds a simple year-by-year table: savings, payments, credit timing, and net, for at least the first ten years. Present two truths separately: the system saves more than it costs over the term, and the monthly cash position early on depends on financing. This matters because a financed customer experiences the loan payment on every statement; if the proposal only promised payback, the first negative year reads as a broken promise rather than a disclosed outcome.
Practice exercise, self-check rubric, and a preparation sequence
Close the loop by producing one complete mini-proposal from your own household bill, then grade it against a written rubric. Repeat the cycle with a different rate type until the translation feels mechanical.
Exercise: take your own redacted utility bill or a published sample tariff. Classify the rate structure, extract annual kWh and the export-credit rule, estimate production for a hypothetical 6 kW array using stated derate assumptions, compute two financial metrics, and write a three-sentence customer explanation of the headline number. Expected observations: your specific yield should land in a plausible band for the site, your blended savings value should differ from the raw retail rate whenever export is involved, and your explanation should survive without the words 'derate' or 'IRR.'
Adaptable sequence: spend week one classifying rate structures from real bills; week two on production math, rebuilding one estimate by hand from irradiance to yield; week three computing all four financial metrics for one system and writing the matching customer sentence for each; week four running timed case drills, including the two scenarios above with changed numbers, and finishing with question practice such as the free practice materials on this site. For scheduling, fees, and format rules, rely on NABCEP's own certification pages rather than summaries.
- Rubric, 1 point each: rate structure correctly named; export-credit rate stated before sizing; every production assumption listed; specific yield inside a plausible site band; metric chosen matches the stated customer goal; caveats and exclusions written in plain language. Six of six suggests the workflow is solid; below four, repeat the exercise with a different tariff.
References and further reading
Use these references to explore the concepts and check the latest information from the relevant organizations.