Comparing SunEarth, Silicon Solar and SOLETKS flat-plate collectors is not a matter of choosing the highest efficiency printed on a product page. The first task is to identify who manufactures the proposed collector, who holds its certificate, which exact model will be delivered, and whether every performance value uses the same area and test basis.

There is no defensible universal winner. There is only a collector whose evidence, duty-point output, structure, hydraulics, delivery scope and lifecycle support best match a specific project.

First, correct the product identities

Search results and distributor pages often mix companies, product families and legacy documents. An EPC buyer should freeze the following four identities before comparing any number.

For the representative products in this guide, the current public evidence reads as follows.

Certificate status checked in the ICC-SRCC main directory on September 1, 2026. Status can change — recheck at bid submission, purchase order and delivery.

Why the identity check prevents expensive mistakes

A distributor may publish a valid certificate for an older model while quoting a newer revision. A current web page can also combine a legacy title with a new SKU. The EPC team should require a one-page model cross-reference, signed by the supplier, that traces the full chain end to end.

Side-by-side published data: useful, but not yet a performance ranking

The table below uses one currently marketed representative model from each route. It is a procurement map — not a declaration that the three collectors are equivalent.

Sources: SunEarth ThermoRay Blue product page, March 2026 spec sheet, TRB-32 OG-100 certificate, Silicon Solar listing, SunMaxx ALDH29-V3 page, and the SOLETKS FPC200 product page. Rounded metric conversions are for screening only — use native certified values in final calculations.

The only fair way to compare thermal performance

For a glazed liquid collector, an ISO 9806–derived efficiency relationship is commonly expressed as:

Useful instantaneous power is then calculated using the same area basis attached to those coefficients. Gross-area coefficients cannot be applied to aperture area, and aperture-area coefficients cannot be applied to gross area. Inlet-temperature and mean-temperature coefficient sets also should not be mixed. The applicable ICC-SRCC OG-100 certificate or Solar Keymark datasheet should state the convention.

Do not compare these four numbers as if they were one metric

SunEarth's TRB-32 certificate publishes gross-area coefficients of η₀ = 0.753, a₁ = 3.753 W/(m²·K) and a₂ = 0.0067 W/(m²·K²). The SunMaxx ALDH29-V3 OG-100 report publishes gross-area coefficients of η₀ = 0.737, a₁ = 3.400 W/(m²·K) and a₂ = 0.014 W/(m²·K²) — model-specific test inputs, not rounded marketing efficiencies.

The SOLETKS FPC200 page publishes a 0.78 peak efficiency, 0.53 rated efficiency and a "total heat-loss coefficient" of 5.4 W/(m²·K), but does not publish a separate a₁/a₂ pair on that page. Do not relabel the 5.4 value as a₁ or invent an a₂ — obtain the exact model's full certificate and report before inserting it into the same calculation.

A normalized OG-100 example for the two US-listed models

The OG-100 Category C condition represents an inlet-to-ambient temperature difference of 20°C. Per-square-meter figures below are derived from each certificate's gross area so panel size does not create a false advantage.

The larger TRB-32 produces more per panel, but its normalized values are close to the ALDH29-V3 values under these standard conditions. That is the useful conclusion — not that either model "wins." Local weather, operating temperature, incidence angle, field hydraulics and load utilization can outweigh the small normalized difference.

Use three duty points, not one brochure condition

For each row, require gross collector area, aperture area, efficiency, watts per collector, watts per square meter of roof envelope, flow, pressure drop and uncertainty. Then run the same collector files through an hourly system model with storage, pipe loss, pump electricity, heat-exchanger approach temperature and load timing. If a supplier cannot reproduce the calculation from a certificate or laboratory report, treat the quoted output as a marketing claim rather than a design input.

A 100 m² gross-module-area layout example

Module size changes panel count, roof packing, lifting and manifold complexity even when the nominal field size is the same. Because current SunEarth documents do not state TRB-32 aperture area, the calculation below uses gross module area for all three products and rounds up to at least 100 m². It is a logistics example, not a thermal-sizing method.

This is not an energy-yield or equal-aperture calculation. It shows why "price per panel" is a poor procurement metric. A smaller panel can add connections and handling operations; a larger panel can reduce module count but demand more lifting space. Final field area must include inter-panel gaps, pipe corridors, roof edges, fire/access routes, tilt-row spacing and maintenance clearances.

The structural engineer must add: mounting rails, brackets, anchors and ballast; operating fluid and trapped water; headers, valves, insulation and cable/control hardware; snow, wind uplift and seismic actions where applicable; load concentration at attachment points; and temporary construction and maintenance loads.

SunEarth ThermoRay: what to verify

SunEarth's current website describes ThermoRay as a liquid flat-plate collector family and identifies ThermoRay Blue as the higher-selectivity option. The ICC-SRCC directory lists TRB-32 and TRB-40 as active OG-100 models through October 1, 2026.

This gives a US project team a clear model-specific certification route, but the date deserves attention: a certificate active during tender may be close to expiration by shipment or commissioning. The purchase order should require active status, or an authority-accepted alternative, at the milestone relevant to the incentive, permit or specification.

For a TRB-32 offer, request: certificate No. 10001804 and its complete rating pages; the current ThermoRay Blue specification-sheet revision; the current gross, aperture and absorber-area definitions used for layout and performance calculations; the selected connection option and compatible seals; pressure-drop data for the exact fluid concentration and design temperature; maximum panels per bank and reverse-return/manifold requirements; approved mounting details and project-specific wind/snow checks; and warranty terms, local service route and spare seals or glazing components.

Silicon Solar and SunMaxx TitanPower: compare the quoted model, not the storefront

Silicon Solar's solar-hot-water category states that it is an official online retailer for SunMaxx collectors and components. Its current flat-plate listing is dispatched and sold by Silicon Solar, while the page describes the collector as a SunMaxx product and directs buyers to SunMaxx mounting hardware.

That relationship is not a quality problem; distributors are normal in solar procurement. It is a documentation problem only when the quotation, certificate and delivered label do not use the same model identity.

The ICC-SRCC directory currently includes several active SunMaxx TitanPower records. For the V3 product, the relevant starting point is TitanPowerPlus ALDH29-V3, certificate No. 10002034, listed active through May 1, 2027. Require Silicon Solar to state in the quote whether that is the exact delivered model. If the quote instead identifies ALDH29, ALDH29-A or another variant, use that model's separate directory record and rating sheet.

The current SunMaxx technical page publishes 2.74 m² gross area, 2.57 m² aperture area, 42 kg dry weight, 1.9 L fluid capacity, 10 bar maximum pressure, 200°C stagnation temperature, 3/4-in press fittings and a suggested flow range of 0.2–0.5 gpm. It also describes a double-header serpentine arrangement and up to 14 collectors per row. These are useful design inputs, but the engineer should reconcile every field with the released datasheet and installation manual supplied for the purchase order.

The commercial submittal should also separate: Silicon Solar's seller obligations and return/freight terms; SunMaxx's manufacturer warranty and any installer conditions; certificate-holder obligations; responsibility for array design and mounting selection; and who provides commissioning, replacement parts and technical support at the project location.

SOLETKS FPC200: what the public product page establishes

The current SOLETKS engineering-specific collector page identifies FPC200 as a 2000 × 1000 × 80 mm, 2.0 m² gross / 1.87 m² aperture collector with 30 kg net weight, 0.6 MPa working pressure, four G3/4 male ports, 1.6 L fluid capacity and 100°C maximum operating temperature. It publishes peak efficiency of 0.78, rated efficiency of 0.53 and a total heat-loss coefficient of 5.4 W/(m²·K).

           

Those fields support early layout and hydraulic discussions. They do not replace the model-specific certificate package needed for a regulated tender. The page refers to CE and Solar Keymark at company/product-range level, so the bid should include:

• Current Solar Keymark certificate and full annex naming FPC200, or the exact offered variant

• ISO 9806 test report with certified η₀, a₁, a₂ and incidence-angle modifiers

• Gross/aperture reference area and temperature convention for every coefficient

• Proof/test pressure in addition to the 0.6 MPa working pressure

• Pressure-drop curve by flow and fluid condition

• Stagnation and freeze-resistance data

• Array limit, balancing method and connection accessory schedule

• Mounting drawings and independently checked project loads

• Production inspection, traceability, warranty and spare-parts plan

• Incoterms, packaging density, container/pallet quantities and site supervision terms

For an international EPC purchase, also lock Incoterms, packaging density, container/pallet quantities, marine-corrosion protection, replacement-glass strategy, site supervision and the language/version of all handover documents. For projects that also need larger centralized panels, the related EFPC115/EFPC150 flat-plate collectors and the EFPC integrated thermal module extend the same engineering family to bigger single-panel areas.

The EPC comparison matrix

Use mandatory pass/fail gates before weighted scoring. A high commercial score must never compensate for an absent certificate or a pressure rating below the design requirement.

Stage 1: mandatory gates

Any "fail" or "not submitted" remains a technical deviation until closed.

Stage 2: weighted evaluation

After all mandatory gates pass, a typical commercial project can score the remaining evidence as follows.

Scores should be assigned by a cross-functional team, with written evidence references — not sales impressions.

A 15-document RFQ package

Ask each bidder for the same package so omissions become visible.

• Signed offer and scope-of-supply matrix

• Exact model and revision cross-reference

• Current product datasheet

• Complete certificate and live directory link

• Full ISO 9806 or referenced laboratory report

• Thermal coefficients and calculation workbook

• Pressure-drop curves for proposed fluid and temperature

• Array-layout and hydraulic-balance guidance

• Connection, valve, vent, drain and sensor schedule

• Mounting drawings and allowable-load evidence

• Materials and corrosion-compatibility declaration

• Installation, commissioning and O&M manuals

• Warranty, exclusions and claim procedure

• Factory QA, inspection, packing and traceability plan

• Delivery, spares, training and after-sales responsibility matrix

Red flags during comparison

Pause the evaluation when any supplier:

• Uses the reseller's name where the certificate should name the manufacturer

• Provides a certificate for a sibling model rather than the offered model

• Quotes "82%," "78%" or another peak value without area and temperature basis

• Compares per-panel output despite materially different collector areas

• Labels a test, proof or maximum pressure as continuous working pressure

• Converts stagnation temperature into a promised useful delivery temperature

• Omits pressure drop, pump electricity or maximum bank length

• Uses a generic wind/snow number without mounting configuration and attachment design

• Offers a warranty without stating who honors it in the destination country

• Guarantees annual output without weather, load, controls, storage and system-loss assumptions

Which route fits which buyer?

Final procurement rule

Do not ask, "Which brand has the best collector?" Ask instead:

That question turns a brand comparison into an engineering decision.

Frequently asked questions