Buy vs Build: Solar Proposal Tools — An Honest Cost Comparison

Every growing solar company hits the same question at some point. Sales wants better proposals. The operations team is tired of copy-pasting between a design tool, a spreadsheet, and a Word template. Someone — usually a founder or an ambitious operations manager — says: “Why don’t we just build our own tool?”

We hear this regularly from installers and EPCs evaluating SurgePV, and we understand the appeal. A custom tool feels like control. No per-seat fees, no vendor roadmap to wait on, every field exactly where your team wants it. We also know how these projects usually end, because several of our customers came to us after abandoning in-house builds that consumed 12–18 months and six figures before producing a tool their sales teams refused to use.

This guide lays out the buy vs build decision for solar proposal tools with real numbers. We cover what a commercial platform actually costs, what a custom build actually costs (including the parts nobody budgets for), a break-even model you can run for your own company, and the narrow set of cases where building genuinely makes sense. Our position is clear up front: for installers and EPCs whose business is selling and building solar — not selling software — buying wins almost every time. But we will show you the math so you can test that claim against your own situation.

Quick Answer

Buying a commercial solar proposal tool is the right choice for the vast majority of solar installers, EPCs, and sales organizations. Commercial platforms cost $50–$260 per user per month and deliver design, simulation, financial modeling, and branded proposals on day one. Building in-house costs $150,000–$500,000 in year one, takes 6–18 months, and carries a permanent maintenance burden of 15–25% of the build cost per year. Build only if proposal software is your core product, or if your requirements are truly unservable by any existing vendor — a bar very few solar companies actually meet.

In this guide:

• What “buying” and “building” actually include, line by line
• Real 3-year cost comparison with named sources
• The hidden costs of in-house builds that sink most projects
• A break-even model with specific seat-count thresholds
• What most solar companies get wrong about “custom”
• The narrow cases where building wins
• A 5-question decision framework you can apply this week

---

What Buy vs Build Actually Means for Solar Proposals

Buying a solar proposal tool means subscribing to a commercial platform that handles design, simulation, and proposal generation for $50–$260 per user per month. Building means hiring or contracting developers to create a custom application — a project that realistically costs $150,000–$500,000 before the first proposal goes out.

The two options sound comparable. They are not. A solar proposal tool is not a form that spits out a PDF. Under the hood it requires:

• A design engine — 3D roof modeling or layout import, module placement, string sizing
• A simulation engine — irradiance data, shading analysis, hourly or sub-hourly yield modeling
• A financial engine — payback, internal rate of return (IRR), net present value (NPV), tariff and incentive logic per market
• A component database — thousands of modules and inverters, updated as datasheets change
• A proposal layer — branded templates, e-signature, analytics, tracking
• Infrastructure — hosting, rendering, storage, security, backups

When you buy, you rent all 6 layers for a subscription fee. When you build, you own all 6 layers — including the ones you forgot to budget for. That difference drives everything else in this guide.

At-a-Glance: Buy vs Build Comparison

The table below compares the two paths across the factors that decide the outcome for most solar companies.

Factor	Buy (Commercial Platform)	Build (Custom In-House)	Winner
Year-one cost	$600–$3,100 per user	$150,000–$500,000+	Buy
Time to first proposal	Same day to 2 weeks	6–18 months	Buy
Ongoing cost	Predictable subscription	15–25% of build cost per year	Buy
Component database	Vendor-maintained, multi-region	You maintain it forever	Buy
Tariff/incentive updates	Vendor updates per market	Your dev team tracks policy	Buy
Feature velocity	Weekly to monthly releases	Competes with your other priorities	Buy
Customization depth	Templates and settings	Unlimited (at a price)	Build
Data ownership	Vendor-hosted, exportable	Full control	Build
Vendor risk	Price changes, roadmap shifts	None (but key-person risk)	Tie
IT overhead	Near zero	Full DevOps responsibility	Buy
Scalability cost	Linear per seat	Near-zero marginal per user	Build (at large scale)
Competitive differentiation	Same tools as competitors	Potentially unique	Build

Buying wins on 8 of 12 factors. Building wins on customization, data control, and marginal cost at very large scale. The question is whether those 3 factors justify the cost and risk — and for most solar companies, they do not.

The Real Cost of Buying a Solar Proposal Tool

Commercial solar proposal and design platforms cost between $50 and $260 per user per month in 2026, with most professional teams landing in the $100–$200 range. A 10-person sales and design team typically spends $12,000–$30,000 per year, all-in.

Pricing across the market is reasonably transparent, with one notable exception. Aurora Solar does not publish pricing; our own Aurora Solar review pegs estimated costs at $220–$259 per user per month, or $2,640–$6,000+ per user per year. OpenSolar offers a free tier aimed at residential installers, monetizing through hardware and financing partnerships. SurgePV publishes per-plan pricing on the pricing page, with design, simulation, financials, and proposals included in a single subscription.

Here is what a realistic annual “buy” budget looks like for a mid-size installer:

Team Size	Low-End Tool ($50/user/mo)	Mid-Tier ($120/user/mo)	Premium ($260/user/mo)
3 users	$1,800/yr	$4,320/yr	$9,360/yr
10 users	$6,000/yr	$14,400/yr	$31,200/yr
25 users	$15,000/yr	$36,000/yr	$78,000/yr
50 users	$30,000/yr	$72,000/yr	$156,000/yr

Two things stand out. First, even premium pricing for a 25-person team costs less per year than the maintenance bill on a mid-range custom build. Second, the subscription includes continuous updates — new modules in the database, new tariff logic, new proposal features — with zero additional spend.

The free option deserves a mention. Tools like OpenSolar can genuinely cover basic residential proposals at no cost. We compared the tradeoffs in our guide to free vs paid solar design software. The short version: free tools work until you need commercial project support, custom branding control, or accurate shading analysis.

The Real Cost of Building Your Own

Building a custom solar proposal tool costs $150,000–$500,000 in year one for a minimum viable product, based on standard software development rates. That estimate assumes a small team of 2–3 developers plus a designer, working 6–12 months.

The inputs behind that range are not exotic. The U.S. Bureau of Labor Statistics reports a median software developer salary above $130,000 per year according to the U.S. Bureau of Labor Statistics, 2024 — and that is salary alone, before benefits, equipment, management overhead, and recruitment cost, which typically add 30–40%. Contracting to an agency shifts the cost rather than removing it: agency rates of $80–$150 per hour produce similar totals for the same scope.

A realistic year-one build budget for a proposal-only tool (no full design engine, just layout import, pricing, and PDF output) looks like this:

Cost Item	Low Estimate	High Estimate
Backend developer (12 months)	$95,000	$140,000
Frontend developer (9 months)	$70,000	$105,000
UI/UX designer (3 months)	$18,000	$35,000
Component/tariff data licensing	$5,000	$30,000
Hosting, rendering, storage (year 1)	$6,000	$24,000
Project management overhead (20%)	$30,000	$60,000
Year-one total	$224,000	$394,000

And that budget assumes the project goes to plan. Most do not. Large IT projects run 45% over budget and 7% over time while delivering 56% less value than predicted, according to McKinsey & Company and the University of Oxford, 2012. Apply the 45% overrun to the mid-point and a “$250,000 build” becomes a $360,000 build — before you have simulated a single kilowatt-hour.

Note what is not in this table: a shading engine, hourly yield simulation, or a financial model with IRR and NPV. Those layers add another 6–12 months of specialist work. A genuine physics-based shading model is a research-grade project, not a feature ticket. This is why most in-house “proposal tools” end up as quoting spreadsheets with a logo on the PDF — the engineering layers get descoped when the budget reality lands.

The Hidden Costs That Kill In-House Builds

The maintenance burden on custom software runs 15–25% of the original build cost every year, forever. For a $300,000 proposal tool, that is $45,000–$75,000 annually — before a single new feature ships.

Software maintenance commonly consumes 50–80% of total cost of ownership over a system’s life, with integration-heavy business tools at the top of the range, according to Pegotec’s maintenance benchmark analysis, 2026. Solar proposal tools are integration-heavy by definition. Here is what the maintenance bill actually buys:

• Component database upkeep. Module and inverter datasheets change monthly. Panels go end-of-life; new TOPCon and heterojunction models ship. Someone must curate this data or your proposals quote discontinued hardware. Budget 0.5–1 full-time equivalent.
• Tariff and incentive tracking. Net metering rules, feed-in tariffs, and tax incentives shift across every market you sell in. When California moved to NEM 3.0, every proposal tool in that market needed new export-rate logic within weeks.
• API and integration churn. E-signature providers, mapping APIs, and irradiance data sources all version their APIs. Each breaking change is an unplanned dev sprint.
• Security and hosting. Patching, backups, uptime monitoring, and data protection compliance are now your job.
• Key-person risk. If the one developer who understands the shading code leaves, you own a black box.

The least visible cost is feature lag. While your team maintains what exists, commercial vendors ship. Bought software compounds in value; custom software decays unless you keep feeding it. The pattern holds across industries: companies that buy rather than build SaaS avoid the cancellation and stall rates of internal projects, and shift the entire upgrade burden to the vendor, as Zylo’s build vs buy analysis, 2026, summarizes.

Break-Even Math: When Does Building Pay Off?

Building a solar proposal tool only beats buying at roughly 150–200 active proposal users — a scale almost no installer or EPC reaches. Below that threshold, the subscription is simply cheaper than the maintenance bill alone.

Here is the model, using conservative numbers from the sections above:

Scenario	3-Year Buy Cost (Mid-Tier, $120/user/mo)	3-Year Build Cost
10 users	$43,200	$300,000 build + $135,000 maintenance = $435,000
25 users	$108,000	$435,000
50 users	$216,000	$435,000
100 users	$432,000	$450,000
150 users	$648,000	$465,000

The crossover arrives somewhere between 100 and 150 sustained users — and only if the build stays on budget, which the McKinsey data says is unlikely. Even then, the comparison is unfair to the build option, because the $120-per-month platform in year 3 is a better product than the one in year 1, while the custom tool is 3 years older.

Run the same math from the value side and buying looks stronger still. If a proposal tool saves each salesperson 3 hours per week — a conservative figure versus spreadsheet workflows — that is 150 hours per person per year. At a fully loaded $50 per hour, a 10-person team recovers $75,000 annually against a subscription cost of $14,400. Speed matters beyond labor savings: faster, more accurate proposals directly lift close rates, as we covered in our analysis of how solar proposal software increases sales and in the solar proposal win rate benchmarks data. A build that takes 12 months to reach parity forfeits a full year of that value.

What Most Solar Companies Get Wrong About “Custom”

The most common mistake in this debate is confusing “we want it our way” with “our way is genuinely unique.” In our experience, roughly 9 in 10 requirements that solar companies call custom are actually configuration: logo placement, pricing markups, financing options, proposal section order. Any credible commercial platform handles these in settings, not code.

The second misconception is that owning the tool means owning an advantage. Your competitors using the same commercial platform still win or lose deals on price, speed, trust, and installation quality — not on whose PDF has a custom font. The proposal is packaging for the offer; the offer is the product.

The third error is underestimating the data layer. Solar companies imagine the hard part is the interface. The hard part is keeping 5,000 component datasheets, 40 tariff structures, and 15 incentive programs accurate at the same time. That is an operations team, not a feature.

The honest tradeoff cuts both ways, though. Buying means accepting vendor risk: price increases, roadmap decisions you do not control, and the possibility a feature you love gets deprecated. Companies with strict data-residency requirements or air-gapped environments may also find commercial cloud platforms simply ineligible. These are real constraints — they just apply to a small minority of the market.

When Building Actually Makes Sense

Building a solar proposal tool is justified in exactly 3 situations: when proposal software is your product, when your workflow is provably unservable by vendors, or when you sustain 150+ proposal users and can fund a permanent product team.

Situation 1: You are a software company. If you plan to sell the tool to other installers, the build cost is R&D for a product line, not an internal IT expense. That is a legitimate bet — it is the one we made with SurgePV. It is also a full-time, multi-year commitment with a marketing budget attached, not a side project for your IT department.

Situation 2: Genuinely unservable requirements. A utility-scale developer running proprietary grid-interconnection cost models, or a financier with a non-negotiable risk-scoring algorithm, may find no vendor willing to build their logic. Even here, the better pattern is usually hybrid: buy the design and simulation layers, build only the proprietary scoring layer on top via exports or APIs.

Situation 3: True scale. A national installer with 200+ active sales users, an existing engineering org, and a 5-year commitment can make the math work. Note the qualifiers: existing engineering org, and permanent funding. The build is the cheap part; the forever team is the real cost.

If none of these describe your company, buying is not the lazy option. It is the rational one.

A 5-Question Decision Framework

You can settle the buy vs build question for your company in one meeting by answering 5 questions honestly. Four or more “buy” answers means the debate is over.

#	Question	If Yes	If No
1	Is selling proposal software part of your business model?	Consider build	Buy
2	Have 2+ vendors confirmed they cannot meet your core requirements?	Consider build	Buy
3	Can you fund a permanent team of 2+ engineers plus $50,000+/yr in data and infrastructure?	Consider build	Buy
4	Do you sustain 150+ active proposal users?	Consider build	Buy
5	Can your sales team wait 12–18 months for a tool that matches what vendors ship today?	Consider build	Buy

Two practical additions. First, pilot before you commit either way: run a 30-day trial on a commercial platform with your 3 best salespeople and measure proposal turnaround time. Second, if you operate in India’s installer market — where DISCOM approval paperwork and WhatsApp-driven follow-up dominate the sales workflow — the CRM side of the stack matters as much as the proposal engine. Our sister team covers that ground in the guide to solar CRM software for Indian businesses, and the design-services perspective in Heaven Designs’ solar proposal software overview.

For teams still mapping what a proposal tool should include before evaluating vendors, our breakdown of solar proposal software features is the right checklist, and the commercial solar proposals guide covers the C&I-specific requirements.

Frequently Asked Questions

The Bottom Line

The buy vs build debate for solar proposal tools has a lopsided answer. Commercial platforms deliver design, simulation, financials, and branded proposals for $50–$260 per user per month, maintained by teams whose full-time job is keeping that product current. A custom build costs more in maintenance alone than most teams would ever spend on subscriptions — and it ships 12–18 months late against a moving target.

Your next steps:

• Run the 5-question framework from this guide with your operations and sales leads this week. If 4 or more answers point to “buy,” close the debate.
• Pilot 2 commercial platforms with your best salespeople for 30 days and measure proposal turnaround time and close rate before committing.
• Send your “custom” requirements list to vendors before funding any build. If 8 of 10 are covered by configuration, you just saved $300,000.

Modern customer-ready solar proposals is a solved problem. A good PV design software platform already combines 3D design, solar shadow analysis software, yield and financial modeling, and proposal generation in one subscription — no developers, no 18-month roadmap, no maintenance bill. The advantage goes to the company that sells more solar this quarter, not the one that builds a tool by next year.