--- title: "PVWatts DC capacity, AC power, and energy outputs" description: "Read PVWatts capacity, hourly power, and monthly energy fields with their units. Use a synthetic report and worksheet before reviewing a solar proposal." canonical: "https://scalewithsearch.com/articles/pvwatts-dc-capacity-ac-power-energy-output-review" --- ## Site navigation - [Scale With Search](https://scalewithsearch.com/) - Services - Services - [AI systems](https://scalewithsearch.com/ai-systems) - [Site build](https://scalewithsearch.com/work#site-build) - [Whole website fix](https://scalewithsearch.com/work#whole-website-fix) - [Content library with SEO](https://scalewithsearch.com/work#content-library) - [Working session](https://scalewithsearch.com/audit) - Start here - [Send your brief](https://scalewithsearch.com/work#send-your-brief) - [Example scope](https://scalewithsearch.com/work#review-the-example-scope) - [Prices and terms](https://scalewithsearch.com/work#prices-and-terms) - Industries - Real estate - [Real estate agents and teams](https://scalewithsearch.com/for/real-estate) - [Platforms, ownership, and IDX](https://scalewithsearch.com/for/real-estate/real-estate-website-platforms-ownership-idx) - [Search, content, and AI](https://scalewithsearch.com/for/real-estate/real-estate-search-content-ai) - [Inquiries, campaigns, and handoffs](https://scalewithsearch.com/for/real-estate/real-estate-website-inquiries-campaigns-handoffs) - [Buyer, seller, and local pages](https://scalewithsearch.com/for/real-estate/real-estate-buyer-seller-local-resources) - [Rules, privacy, and trust](https://scalewithsearch.com/for/real-estate/real-estate-website-rules-privacy-trust) - Browse by business - [Trades and home services](https://scalewithsearch.com/for/#group-trades) - [Health, wellness, and animal care](https://scalewithsearch.com/for/#group-practices) - [Law, finance, and IT](https://scalewithsearch.com/for/#group-professional) - [Marketing and SEO agencies](https://scalewithsearch.com/for/#group-agencies) - [Shops and manufacturers](https://scalewithsearch.com/for/#group-manufacturing) - [Restaurants, shops, studios, and nonprofits](https://scalewithsearch.com/for/#group-local-services) - Chiropractic practices - [Chiropractic and wellness practices](https://scalewithsearch.com/for/chiropractic-and-wellness-practices) - [Chiropractic and physical therapy clinics](https://scalewithsearch.com/for/chiropractic-and-physical-therapy-clinics) - [All industries](https://scalewithsearch.com/for/) - Resources - Free tools - [AI readiness check](https://scalewithsearch.com/check) - [Free tools](https://scalewithsearch.com/tools/) - [Free Starter Kit](https://scalewithsearch.com/kit/business-memory-starter-kit.zip) - Guides - [AI-native library](https://scalewithsearch.com/ai-native) - [Industry intelligence](https://scalewithsearch.com/intelligence) - [Office job guides](https://scalewithsearch.com/guides/) - [Business memory](https://scalewithsearch.com/articles/business-memory-for-ai-agents-guide) - [Agent governance](https://scalewithsearch.com/articles/ai-agent-governance-guide-small-business) - [Migration and ownership](https://scalewithsearch.com/articles/leaving-vendor-ai-memory-guide) - Articles - [All articles](https://scalewithsearch.com/articles/) - [What changed](https://scalewithsearch.com/changes/) - About - Evidence - [Proof](https://scalewithsearch.com/proof) - Scale With Search - [About](https://scalewithsearch.com/about) - [How it works](https://scalewithsearch.com/how-it-works) # PVWatts capacity and energy outputs: keep DC size, AC power, and kilowatt-hours separate A solar proposal can show system size, an hourly output column, and an annual production total on the same page. Before comparing those figures, identify what each number measures. A capacity input, a power value, and accumulated energy answer different questions. Start the review by adding three labels to each figure: quantity, unit, and period. Then identify whether it came from a model input, a modeled result, or an operating measurement. This small annotation exercise makes the rest of the technical discussion easier to follow. The [solar installation page](/for/solar-installation) introduces office work around approved job records. This guide supplies a worksheet for one narrower task: explaining the numbers in a production report before a proposal review. ## Give power and energy different columns The [US Energy Information Administration's electricity measurement guide](https://www.eia.gov/energyexplained/electricity/measuring-electricity.php) distinguishes power from energy over time. A kilowatt equals 1,000 watts. One kilowatt maintained for one hour corresponds to one kilowatt-hour. Keep the difference visible in spreadsheet headings. Write “Power, W AC” for a power series and “Monthly energy, kWh AC” for a monthly total. Avoid a heading such as “Output” when the sheet mixes both quantities. For a synthetic constant-power example, 2 kW maintained for three hours produces 6 kWh. The multiplication includes time. Changing the label on 2 kW to 2 kWh would omit that step and leave the duration unspecified. Similarly, an energy total of 600 kWh over 300 hours implies an average power of 2 kW over that interval. It does not show that output stayed at 2 kW throughout. A total and an average cannot reproduce the sequence of individual power values. These arithmetic examples describe no roof, equipment package, or production expectation. Use them to check the calculation method before entering a real proposal's numbers. ## Read the selected PVWatts field dictionary The [PVWatts V8 API documentation](https://developer.nlr.gov/docs/solar/pvwatts/v8/) defines the fields below. The monthly arrays run from January through December. Hourly fields require the hourly output setting. | Field | Documented quantity and unit | | --- | --- | | `system_capacity` | Nameplate capacity, kW | | `dc` | Hourly DC output, W DC | | `ac` | Hourly AC output, W AC | | `dc_monthly` | Monthly DC energy, kWh DC | | `ac_monthly` | Monthly AC energy, kWh AC | | `ac_annual` | Annual AC energy, kWh AC | | `poa` | Hourly plane-of-array irradiance, W/m² | | `poa_monthly` | Monthly plane-of-array irradiation, kWh/m² | Copy the field identifier into your review record. Preserve DC or AC in the display label. Also keep the area denominator on radiation fields. A number expressed per square meter cannot become whole-system electrical energy through a label change. If a proposal application renames these fields, ask for its mapping. For example, a heading reading “Annual output” should point to the exact underlying field. Record any conversion or rounding between the original result and the displayed number. Treat a report without a field mapping as incomplete evidence. The preparer can resolve the missing definition before the team debates a difference between two tables. Do not choose a field based on whichever number seems more plausible. ## Annotate a synthetic report excerpt The following values are invented for this worksheet. They are not a PVWatts response, a simulated property, or a recommended system design. Assume the preparer identifies the capacity input as DC module nameplate capacity. | Synthetic report item | Value | Review annotation | | --- | --- | --- | | Capacity input | 6 kW DC | Assumed design input | | One hourly AC value | 2,400 W AC | Power for the selected hourly record | | January AC energy | 500 kWh AC | One monthly total | | February AC energy | 600 kWh AC | A different monthly total | | Sum of all twelve monthly AC totals | 8,100 kWh AC | Annual arithmetic check | | Displayed annual AC energy | 8,100 kWh AC | Agrees with the synthetic monthly sum | The hourly value converts to 2.4 kW AC. Under a stated one-hour, constant-power teaching assumption, that interval would contribute 2.4 kWh AC. Keep the assumption beside the arithmetic. Do not apply an hourly conversion to a series with an unknown interval. January and February can be compared as monthly energy totals. February exceeds January by 100 kWh AC in this example. Relative to January, the increase is 100 divided by 500, or 20 percent. That calculation does not explain the difference. It does not establish better equipment, improved operation, or a weather effect. The worksheet contains two totals and their arithmetic relationship. A causal explanation needs separate evidence. The twelve synthetic monthly AC totals, January through December, are 500, 600, 700, 750, 800, 850, 850, 800, 700, 600, 500, and 450 kWh. Their sum is 8,100 kWh AC. These invented values complete the worksheet example; they describe no location or expected seasonal pattern. The annual sum provides another useful check. Ask the preparer to reconcile the twelve original monthly values against the annual field. Use unrounded values when available. If only rounded displayed values remain, record the precision limit before declaring a discrepancy. ## Do not add unlike quantities Adding the 6 kW capacity input to January's 500 kWh total produces no useful combined quantity. The units differ. Keep them in separate worksheet sections even when the proposal places them side by side. Adding monthly DC energy to monthly AC energy also fails the intended report review. Those are separate output measures. Ask which boundary the comparison needs, then select the matching series for both reports. For example, suppose a second synthetic table lists January DC energy of 540 kWh DC. Comparing that with 500 kWh AC reveals an arithmetic difference of 40 kWh. Calling the difference an independently verified inverter loss would add a conclusion the excerpt cannot establish. Instead, write: “Different output boundaries; request the matching model definitions and assumptions.” That note states the problem without assigning its cause. It also gives the technical reviewer a specific follow-up action. The same discipline applies to a bill or meter export. Ask what the instrument measures and which dates it covers. Do not assume its number matches the production boundary used in the model merely because both values use kWh. ## Check time steps before summing a series Before aggregating exported values, document the time basis. Ask whether each row represents power, interval energy, or a cumulative reading. Obtain the export's timestamp convention and interval duration from its preparer. For a teaching series of three one-hour average power values, use 1 kW, 2 kW, and 3 kW. Multiplying each value by one hour gives 1, 2, and 3 kWh. Their energy sum is 6 kWh. Now change only the interval to thirty minutes. Those same three average power values yield 0.5, 1, and 1.5 kWh. The sum becomes 3 kWh. The numerical power values stayed unchanged; the duration changed the accumulated energy. These examples explain why a copied column needs its interval definition. They do not prescribe a conversion for every export. For an actual hourly PVWatts series, retain the documented field meaning and ask the preparer to explain its aggregation method. Inspect missing and repeated intervals before calculating totals. If the file lacks a timestamp explanation, leave aggregation unresolved. Preserve the original export rather than silently filling gaps or deleting duplicate-looking rows. ## Keep model assumptions beside the result V8 documents `dc_ac_ratio` as the DC-to-AC ratio, `inv_eff` as inverter efficiency at rated power, and `losses` as system losses in percent. It also returns service-version and SSC-library information. See the [request and response definitions](https://developer.nlr.gov/docs/solar/pvwatts/v8/). Ask the preparer which values were entered and which defaults were retained. A report's annual total alone cannot answer those questions. Keep the original input record with the result so another reviewer can inspect the same assumptions. Do not treat a documented default as an equipment recommendation. The review task is to identify what the estimate used. Equipment selection and the suitability of an assumption remain questions for the responsible technical professional. When comparing report versions, make a change list before comparing their totals. Record changed capacity, orientation, loss assumptions, inverter settings, and weather selection. Ask the preparer which changes were intentional. If several inputs changed, avoid attributing the total difference to one setting. A controlled comparison would need a clearly defined method. Your initial worksheet can flag the unresolved explanation without attempting a new model run. ## Use a review worksheet with named ownership This worksheet is an editorial recommendation. Adapt it to the report format your installer uses. The purpose is to preserve the explanation behind the numbers, rather than produce another unexplained summary. | Review field | What to record | | --- | --- | | Report identity | Filename, revision, preparation date, and preparer | | Model identity | Selected version and available library information | | Capacity basis | Original input, unit, and DC or AC designation | | Selected output | Exact field, unit, time step, and system boundary | | Aggregation | Included intervals, conversion, rounding, and missingness | | Assumption record | Entered values, retained defaults, and unresolved settings | | Comparison | Matching field in the second report and any incompatibility | | Review decision | Accept the explanation, request evidence, or hold comparison | Assign one person to prepare the record and one qualified person to check the technical interpretation. Where a field remains unknown, name the person who must supply it. An empty cell should not silently mean that a default was used. Keep the decision narrow. “Monthly arithmetic reconciled” does not mean “proposal design approved.” Write separate decisions when different reviewers own arithmetic, equipment assumptions, and customer-facing explanations. ## Explain the result without turning it into a commitment For the synthetic excerpt, an appropriate explanation is: “The worksheet uses 6 kW DC as its capacity input and totals 8,100 kWh AC annually.” Follow it with the model basis and unresolved assumptions. Do not replace that explanation with a claim about what a buyer will receive. PVWatts' [interpretation guidance](https://pvwatts.nlr.gov/docs/en/help_results_interpret.php) explains that weather and operating conditions affect modeled results. For the weather basis specifically, continue with [typical-year data and production estimate limits](/articles/pvwatts-typical-weather-year-production-estimate-limits). Keep this production worksheet separate from market comparisons. The [solar intelligence overview](/intelligence/solar-installation) addresses public project evidence. A production table requires its own model and measurement definitions. Store the report, field mapping, review questions, and corrections together. The [business memory guide](/articles/business-memory-for-ai-agents-guide) explains how an owned record can preserve that context for later work. Scale With Search can scope a report-review record around your approved documents and review responsibilities. Define the source fields and acceptance checks before building the function. [Discuss the scope](/work) Continue the website review: [AI-native solar installation: the first functions to build](/articles/ai-native-solar-installation-first-functions); [NYSERDA pipeline projects: compare application age before reading completion rates](/articles/nyserda-pipeline-age-completion-cohorts); [NYSERDA project costs: compare reported dollars per DC watt with a solar quote](/articles/nyserda-project-cost-dollars-per-dc-watt); [PVWatts weather data: explain a typical year without promising next year's production](/articles/pvwatts-typical-weather-year-production-estimate-limits); [Solar brochure PDFs: decide what search should find](/articles/solar-brochure-pdf-search-indexing); [Solar installation AI rules: data, approvals, and spend](/articles/solar-installation-ai-data-approval-spend-rules); [Solar project pages: separate installed work from estimates](/articles/solar-installation-project-case-study-page); [Solar installer review requests: keep the wording neutral](/articles/solar-installer-google-review-request-process); [Solar installer local SEO: connect coverage to real proof](/articles/solar-installer-local-seo); [Solar installer videos: give each useful clip a page](/articles/solar-installer-video-website-search); [Solar installer credentials: make website claims precise](/articles/solar-installer-website-certification-claims); [Solar website FAQs: publish answers you can maintain](/articles/solar-installer-website-faq-content); [Solar installer quote form: ask for the first useful facts](/articles/solar-installer-website-quote-form); [Solar website savings claims: show the assumptions](/articles/solar-installer-website-savings-claims); [Solar website warranty page: name the actual coverage](/articles/solar-installer-website-warranty-page); [Solar repair page: separate service from installation](/articles/solar-maintenance-repair-website-page). [solar installers](/for/solar-installation): website and search resources. ## Related: solar installers - [PVWatts weather data: explain a typical year without promising next year's production](/articles/pvwatts-typical-weather-year-production-estimate-limits) - [Solar brochure PDFs: decide what search should find](/articles/solar-brochure-pdf-search-indexing) - [Solar installation AI rules: data, approvals, and spend](/articles/solar-installation-ai-data-approval-spend-rules) ---- ```text .|########||. .|########||. .|########||. |##||. .||##|. |##||. .||##|. |##||. .||##|. |#|. .|#|. |#|. .|#|. |#|. .|#|. |#| |#| |#| |#| |#| |#| .#| |#. .#| |#. .#| |#. .#. .#| .#. .#| .#. .#| |#. .#| |#. .#| |#. .#| |# ...... #| |# ...... #| |# ...... #| .# ||#########| #| .# ||#########| #| .# ||#########| #| .#. |######||######|. .#. .#. |######||######|. .#. .#. |######||######|. .#. #. .##|###|##|#|######| .# #. .##|###|##|#|######| .# #. .##|###|##|#|######| .# || |##|#||||||||||||#||#| || || |##|#||||||||||||#||#| || || |##|#||||||||||||#||#| || # |#||||||||||||||||||||#| #. # |#||||||||||||||||||||#| #. # |#||||||||||||||||||||#| #. || |#||||||||||||||||||||||#| || || |#||||||||||||||||||||||#| || || |#||||||||||||||||||||||#| || # .#||||||||||||||||||||||||#| # # .#||||||||||||||||||||||||#| # # .#||||||||||||||||||||||||#| # || ....|||#||||||##|#|||#|#||##||||....|. || || ....|||#||||||##|#|||#|#||##||||....|. || || ....|||#||||||##|#|||#|#||##||||....|. || #. . ....|# ....#||| ||| .#||| ....#. .# #. . ....|# ....#||| ||| .#||| ....#. .# #. . ....|# ....#||| ||| .#||| ....#. .# # . ||||#| .#####|| . .#| .#||| ||||# #. # . ||||#| .#####|| . .#| .#||| ||||# #. # . ||||#| .#####|| . .#| .#||| ||||# #. .| ||||| #. |#|||||. || #. |#||. .||||| || .| ||||| #. |#|||||. || #. |#||. .||||| || .| ||||| #. |#|||||. || #. |#||. .||||| || || |.... #. ....|#. |. ...|. ....|| || || |.... #. ....|#. |. ...|. ....|| || || |.... #. ....|#. |. ...|. ....|| || #. .||||||##||||||##||####|||||||#||||||#| .# #. .||||||##||||||##||####|||||||#||||||#| .# #. .||||||##||||||##||####|||||||#||||||#| .# # .||####|###########################|. # # .||####|###########################|. # # .||####|###########################|. # # .#||||||.#.|| # |. ..# #| #|||||#| # # .#||||||.#.|| # |. ..# #| #|||||#| # # .#||||||.#.|| # |. ..# #| #|||||#| # # .#|||||| .. |# ## |#| ...#|#|||#| # # .#|||||| .. |# ## |#| ...#|#|||#| # # .#|||||| .. |# ## |#| ...#|#|||#| # # .#|||#|# .# .#| #| ##|.#..#|||||#| # # .#|||#|# .# .#| #| ##|.#..#|||||#| # # .#|||#|# .# .#| #| ##|.#..#|||||#| # # .#||||||############|######|||||#| # # .#||||||############|######|||||#| # # .#||||||############|######|||||#| # # |...||#||||||#||||#|#||||||#|||||#||| |.| # # |...||#||||||#||||#|#||||||#|||||#||| |.| # # |...||#||||||#||||#|#||||||#|||||#||| |.| # #. .. ||||# .|||##|. |#| .|| || .|||#. #| # .# #. .. ||||# .|||##|. |#| .|| || .|||#. #| # .# #. .. ||||# .|||##|. |#| .|| || .|||#. #| # .# || | ...|| ...##| | #| .|. |. ##### .. .| || || | ...|| ...##| | #| .|. |. ##### .. .| || || | ...|| ...##| | #| .|. |. ##### .. .| || || ||||| || ||||#| . |. |. |#. ||||| |#| || || || ||||| || ||||#| . |. |. |#. ||||| |#| || || || ||||| || ||||#| . |. |. |#. ||||| |#| || || .# |.....#|....|#.||||.|||##.|#|....||.#||.#. #. .# |.....#|....|#.||||.|||##.|#|....||.#||.#. #. .# |.....#|....|#.||||.|||##.|#|....||.#||.#. #. #.|||||||#############################| ||| .# #.|||||||#############################| ||| .# #.|||||||#############################| ||| .# || ##||#||#||||||#||#||#||#||##. || || ##||#||#||||||#||#||#||#||##. || || ##||#||#||||||#||#||#||#||##. || # .#|||||||||#||#|||||||||||#| # # .#|||||||||#||#|||||||||||#| # # .#|||||||||#||#|||||||||||#| # || |#||||||||||||||||||||||#| || || |#||||||||||||||||||||||#| || || |#||||||||||||||||||||||#| || .# |#||||||||||||||||||||#| #. .# |#||||||||||||||||||||#| #. .# |#||||||||||||||||||||#| #. || |#||||||||||||||||||#| || || |#||||||||||||||||||#| || || |#||||||||||||||||||#| || #. .######|#|#########| .# #. .######|#|#########| .# #. .######|#|#########| .# .#. |#####||||#####| .#. .#. |#####||||#####| .#. .#. |#####||||#####| .#. |# ||########|| #. |# ||########|| #. |# ||########|| #. |# ...... #| |# ...... #| |# ...... #| |#. .#| |#. .#| |#. .#| |#. .#. |#. .#. |#. .#. .#| |#. .#| |#. .#| |#. |#| |#| |#| |#| |#| |#| .|#|. .|#|. .|#|. .|#|. .|#|. .|#|. |##||. .||##| |##||. .||##| |##||. .||##| .||########||. .||########||. .||########||. 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