MicrogridModeler vs Excel spreadsheets: when is a spreadsheet enough for microgrid sizing in 2026?

Key takeaways

• Excel can hold an 8,760-hour model easily: a worksheet supports 1,048,576 rows. Capacity is not the reason to leave a spreadsheet.
• Excel desktop Solver can optimize an objective under constraints, but Microsoft documents a limit of 200 adjustable cells; that matters when hourly operating decisions themselves become variables.
• A well-built spreadsheet is valuable and auditable. Its formulas, precedent tracing, assumptions, and cash-flow checks can make it the best companion to dedicated microgrid software.
• MicrogridModeler is strongest when the same off-grid PV + battery + diesel dispatch and hard feasibility rules must run repeatedly, deterministically, and in a browser.
• HOMER Pro and REopt become better fits when the project needs broader hybrid technologies, large sensitivity sets, integrated DER optimization, resilience analysis, or programmatic workflows.

Comparison matrix

Direct answer: keep the spreadsheet, but give it the right job

Excel is enough when the main work is cleaning interval data, documenting assumptions, building capital and operating cost schedules, testing a few scenarios, or checking another model. Move to MicrogridModeler when the deliverable depends on repeatable chronological dispatch for an off-grid PV + battery + diesel system and another analyst needs to see whether the same inputs reproduce the same feasible result.

This is not a contest between flexible and serious tools. A disciplined spreadsheet is serious engineering work. The practical dividing line is responsibility: in Excel, the analyst builds and validates the dispatch engine; in MicrogridModeler, that focused engine is already part of the product. HOMER Pro and REopt sit nearby when the study needs broader technologies, larger sensitivity analysis, or formal DER co-optimization.

What spreadsheets do exceptionally well

Spreadsheets are often the best intake and checking layer in a microgrid study. They are familiar to clients, easy to adapt to a procurement schedule, and good at exposing unit conversions and cash-flow logic. Microsoft also provides real analysis tools: Scenarios, Goal Seek, Data Tables, constrained Solver optimization, formula precedent and dependent tracing, and version history for files stored in OneDrive or SharePoint.

That makes “spreadsheets are unauditable” an unhelpful claim. A carefully structured workbook with named inputs, protected formulas, change notes, source citations, test cases, and a clean output sheet can be easier to review than a poorly documented specialist model.

• Inspect and repair an 8,760-row load profile, including gaps, duplicated timestamps, time zones, and daylight-saving transitions.
• Maintain the assumption register for equipment costs, fuel price, escalation, replacements, project life, and discount rate.
• Build vendor quote comparisons and owner-specific cash-flow schedules.
• Create quick one- and two-variable scenario tables for fuel price, load growth, battery cost, or solar yield.
• Cross-check annual energy balances, diesel consumption, replacement timing, net present cost, and LCOE from another model.

8,760 rows are not the same as 8,760 decision variables

Excel has no trouble storing one row for every hour of a year. Microsoft documents 1,048,576 rows per worksheet. A spreadsheet can therefore calculate a fixed dispatch policy across 8,760 hours, propagate battery state of charge from one row to the next, and let Solver change a small number of sizing cells.

The important limit is different. Microsoft documents up to 200 adjustable cells in the built-in Solver. If every hourly battery charge, discharge, generator output, curtailment, or unmet-load value is treated as a separate optimization variable, a full-year formulation quickly exceeds that built-in limit. An analyst can aggregate time, reformulate the problem, use a third-party solver or code, or keep the hourly rows as a deterministic simulation while optimizing only a few sizes.

That last approach can work well, but model quality then depends on recurrence and edge cases: starting and ending state of charge, charge and discharge efficiency, simultaneous charging and discharging, generator minimum loading, reserve, curtailment, battery power versus energy, and the exact treatment of unmet load. The fair conclusion is not that Excel cannot model a microgrid. It is that the workbook author owns the engine and its evidence.

Where MicrogridModeler earns its place

MicrogridModeler is designed for the repeated early-stage question behind remote clinics, telecom sites, camps, schools, islands, and industrial loads: what PV, battery, and diesel combination can serve the load under explicit constraints, and what happens to dispatch, fuel use, renewable fraction, and lifecycle economics?

Its value is consistency. The planner does not need to rebuild the hourly state machine for every proposal or assignment. Identical inputs follow the same deterministic workflow, and the result stays connected to the assumptions and dispatch trace. That is useful when several team members must review a screen or when a student needs to explain why a design is feasible rather than only report its LCOE.

The scope is deliberately narrower than a general spreadsheet, HOMER Pro, or REopt. MicrogridModeler should not replace the cost register, a custom finance workbook, or detailed electrical engineering. It should replace the repeated reinvention of a focused off-grid PV + battery + diesel feasibility engine.

When HOMER Pro or REopt is the better next step

HOMER Pro is a strong choice when the concept includes a broader hybrid technology set or when a mature desktop sensitivity workflow is central. UL Solutions currently describes full-year hybrid-microgrid simulation at time steps from one minute to one hour, equipment-configuration evaluation, least-cost optimization, thousands of sensitivity simulations, and optional modules for technologies and workflows beyond a focused PV + battery + diesel screen.

REopt is a strong choice when the problem is best framed as integrated mathematical optimization. Its current public materials describe recommending technology sizes and dispatch across solar, wind, generators, grid electricity, battery storage, and thermal options. The official manual describes a deterministic mixed-integer linear program that meets loads at each time step while minimizing lifecycle cost, with web, API, and open-source access. For off-grid studies, the web tool is narrower: it models PV, battery storage, and generators; generator size is a user input in the web interface and can be optimized through the API.

REopt also states its boundary clearly: the web tool is an energy-balance decision model, not power-flow analysis or procurement-ready detailed design. The same escalation rule applies to every option here. Once voltage, fault current, protection, harmonics, dynamic stability, or stamped design becomes the question, move into the appropriate electrical-study and engineering workflow.

A practical spreadsheet-plus-software workflow

For many EPC and consulting teams, the best answer is not “spreadsheet or software.” It is a controlled handoff between them. Keep the spreadsheet as the commercial and checking layer, and use the purpose-built model for the chronological feasibility calculation.

• Clean the load data in a spreadsheet and document units, missing intervals, time zone, and daylight-saving treatment.
• Keep one source-linked assumption register for capital cost, replacement cost, fuel, efficiencies, project life, and discount rate.
• Run the focused PV + battery + diesel case in MicrogridModeler with explicit unmet-load and renewable-fraction limits, then inspect the built-in operating-reserve and state-of-charge checks.
• Inspect worst-hour dispatch, battery boundaries, generator loading, curtailment, unmet load, and fuel use before accepting economics.
• Cross-check annual energy, fuel, cash flow, NPC, and LCOE in the spreadsheet without copying hidden formulas between cases.
• Escalate to HOMER Pro, REopt, power-flow software, or detailed engineering when the planning question expands beyond the focused screen.

A useful exercise for students

Students should build at least one small spreadsheet dispatch model. It is one of the fastest ways to learn the difference between power and energy, see state of charge propagate through time, and discover how easily a boundary condition changes the answer.

Then run the same load and assumptions in MicrogridModeler. Compare annual energy first, then inspect the hours where the two results diverge. The goal is not to make the numbers match by force. It is to identify which dispatch rule, constraint, efficiency convention, or economic definition explains the difference. That habit transfers to HOMER Pro, REopt, and every serious engineering model.

Bottom line

Keep Excel for the work it does best: data QA, assumptions, custom cost logic, scenarios, and independent checks. Use MicrogridModeler when the core deliverable is repeatable, browser-first, auditable off-grid PV + battery + diesel feasibility. Choose HOMER Pro when hybrid breadth and sensitivity studies matter more, and choose REopt when integrated DER size-and-dispatch optimization is the better formulation.

The most defensible study is usually a small toolchain, not a single winner: one source of assumptions, one purpose-built feasibility engine, one independent arithmetic check, and a clear boundary for when detailed engineering begins.

Continue your comparison

Sources and review notes

This comparison is based on public product and documentation pages reviewed for the 2026 planning context. Always verify current licenses, modules, and pricing before making procurement decisions.

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