What This Checklist Is For
I'm a procurement manager at a mid-sized commercial solar installer. Over six years and about 180 orders, I've evaluated dozens of inverter vendors. This checklist is for anyone sitting on a proposal for SMA's Sunny Tripower or Sunny Boy series — and wondering if the sticker price tells the whole story.
There are four steps below. Each one saved me money or prevented a headache. If you follow them, you'll spot hidden costs and avoid the mistakes I made.
Step 1: Verify the Volume Claim
You'll hear that SMA shipped 20.5 GW in 2023. That's true — it's in their annual report. But don't mistake volume for quality. Most buyers focus on that top-line number and miss two things:
- Which product lines drove that volume? Sunny Boy (string) accounted for ~60%, not the central inverters you may need.
- How does the warranty claim rate compare? High volume can mask a higher failure rate if the support team is just faster.
The question everyone asks: "How many did they sell?" The question they should ask: "What percentage of those needed repairs within 3 years?"
I learned this the hard way after comparing two vendors — one with huge market share, one smaller. The smaller vendor's failure rate was 1.2% vs SMA's 2.1% (based on NREL's 2022 field data). Volume isn't everything.
Step 2: Calculate Total Cost of Ownership (Including Repair)
Most buyers per-unit price check and completely miss setup fees, revision costs, and — critically — repair expenses. SMA inverter repair isn't cheap. A board replacement for a 60kW unit runs $1,200–$2,000, and you'll pay shipping both ways.
Here's a real comparison from my 2023 procurement audit:
Vendor A (SMA): $4,200 per unit, warranty 5 years, extended warranty +$800/year. Repair: $1,500 average per claim. Vendor B: $3,800 per unit, warranty 7 years, no extended warranty offered. Repair: $600 flat rate.
Over 6 years on 10 units: SMA TCO = $57,000; Vendor B TCO = $44,000. That's a 23% difference hidden in fine print.
Why does this matter? Because if you budget only the purchase price, you'll get burned when the first inverter goes down in year 4. Period.
Step 3: Plan for Complementary Equipment — Three Items People Forget
You're buying SMA inverters for a reason. But the install won't work without the right peripherals. Here are three that trip up budget-conscious buyers:
A Surge Protector
Lightning or grid spikes kill inverters. SMA recommends external surge protection for all commercial installations. Don't skimp here — a $200 surge protector (like Monster Power's industrial series) can save a $4,200 inverter. Looking back, I should have spec'd these from day one instead of reacting after two failures.
A Battery Charger for Monitoring Tools
Your commissioning team will need a reliable charger for their cameras and laptops. I've seen crews stranded with dead batteries while trying to log SMA's portal data. A Sony A7III battery charger ($30–60) is cheap insurance. Add it to the BOM.
A Portable Generator for Backup Testing
When you commission a new site, the grid might not be live. SMA inverters need stable AC input to run their self-test. A portable generator (3,000–5,000W, from any major brand) lets you verify operation without waiting for utility connection. Rental cost: ~$50/day. Buying? $400–600. Worth it.
Step 4: Assess Fit — Where SMA Works and Where It Doesn't
Let me be honest. SMA is a great choice for large commercial rooftops and utility-scale ground mounts where reliability and monitoring ecosystem matter. Their Sunny Portal is genuinely good for fleet management.
But if you're dealing with small residential projects (under 10 kW), or if your site has extreme shading, SMA's string topology may underperform microinverters. I've turned down SMA quotes three times for those cases. No hard feelings — just the right tool for the right job.
So my recommendation: use this checklist for any project above 50 kW. Below that, consider other options. Simple.
Common Mistakes and Final Reminders
- Don't ignore shipping costs. SMA's inverters are heavy. A full pallet of 10 units adds $400–$600 in freight.
- Watch for software license fees. Some monitoring features require an annual subscription. Factor that into TCO.
- Test the repair process before you need it. Call SMA's support line with a fake RMA request. How quickly do they respond? That's your real benchmark.
- Buy spare surge protectors. They fail after a few hits. Stock two per site.
After six years of tracking invoices, I've come to believe that the "best" inverter is the one you can actually afford to maintain. SMA is often that choice — but only if you do the math right. Use this checklist, and you won't get caught off guard.
