Case study · Hardware + subscription
Voltwise raises a round shaped by inventory and certification
Voltwise sells a smart home energy monitor for $229 and an app subscription for $9.99 a month. Hardware brings two problems software founders rarely face: cash tied up in stock before anything is sold, and long certification timelines. This case shows how the Hardware edition models both.
- Starting point
- 1,500 active device users, about 40% subscribing, $400k in the bank, a first production run sold through
- Seed round
- $2.50M
- at $10M pre-money
- Series A (plan)
- $9M
- at $36M pre-money
What this case teaches
- Cash need in hardware is driven by inventory and lead times, not only by burn.
- Model device margin and subscription attach separately; investors value them differently.
- Venture debt can extend runway cheaply after equity, if repayments fit the plan.
- A green Health Score does not mean low risk: read the stress test.
The starting point
Voltwise had a product customers loved, a factory partner ready for a larger run, and a cash flow that worked against it.
The first 2,000 devices sold out through the website. Each device cost $95 to build plus $12 to ship, and around 4% came back under returns or warranty. About 40% of active users paid for the app subscription.
The factory needed payment for the next run before units shipped, and the company wanted three months of stock on hand. Ordering the next 6,000 units would cost more than all the cash in the bank, months before a single new device was sold.
What the founders brought to the model
| Input | Value | Source |
|---|---|---|
| Active device users | 1,500 | App database |
| Device price | $229 | Website and retail price list |
| Bill of materials + manufacturing | $95 per unit | Factory quote, 6,000 units |
| Shipping & fulfilment | $12 per unit | 3PL contract |
| Returns & warranty | 4% of device revenue | First production run |
| Subscription attach rate | 40% | App billing |
| Inventory held | 3 months of device cost | Factory lead time + safety stock |
| Cash in bank | $400k | Bank statement |
The first draft, and what the Self-Audit caught
The founders' first version looked great and was wrong in three ways. Each one would have been found in diligence.
| Mistake | First draft | Fixed version | Impact |
|---|---|---|---|
| No inventory | Cash only reflected profit and loss. | Three months of device cost held as inventory in working capital. | Cash needed rose by well over $100k. Without it, the company would have run short just as the production run shipped. |
| Every user a subscriber | Subscription revenue on 100% of active users. | Attach rate of 40%, rising to 60%. | Subscription revenue fell by more than half; device margin became the main driver in years 1-2. |
| Flat costs, no returns | $95 bill of materials forever and no returns. | Volume-based BOM decline, $12 fulfilment and 4% returns. | Year-1 gross margin fell to 53%, then rises to 72% as the subscription base grows. |
The lesson
Hardware models fail on cash timing more often than on profit. The Balance Sheet and Working Capital tabs showed where the money was tied up.
The plan, after the fixes
Revenue doubles in year 2 and reaches $4.7M in year 3. EBITDA stays negative for five years (it turns positive month by month only from month 58) because the plan keeps investing in hardware and channel growth. That is typical for hardware, and the founders said so openly.
Gross margin moves from 53% in year 1 to 72% in year 5, and the team grows from 9 to 30 people.
Sizing the raise
The Raise Planner's minimum ignores the risks the founders worried about most: production timing and certification. The Raise Planner shows only about $1.1M is needed to month 21, rounded to $1.25M. Voltwise raised $2.5M. The Use of Funds plan explains why: 22% goes on the first 6,000-unit production run and tooling, and 6% on CE / UL / FCC certification, which must be paid months before revenue arrives.
Where the money goes
| Category | Share | Buys | Unlocks |
|---|---|---|---|
| Hardware & firmware engineering | 30% | Hardware + firmware engineers, test rigs | Gen-2 device, 15% lower BOM |
| Inventory & manufacturing | 22% | First 6,000-unit production run, tooling | Stock ahead of retail launch |
| App & subscription product | 12% | App engineer, energy insights features | Attach rate above 45% |
| Marketing & retail channel | 14% | Retail Channel Manager, launch campaign | 2 retail partners |
| Certification & compliance | 6% | CE / UL / FCC testing | Certified for EU + US |
| G&A & Operations | 9% | Finance, supply-chain ops, legal | Clean diligence |
| Contingency buffer | 5% | Component price shocks, shipping delays | 2+ months extra runway |
| Recruiting & hiring | 2% | Recruiting fees | Team of 14 by month 18 |
Cap table and ownership
Before the seed, Voltwise had one post-money SAFE ($150k at a $6M cap) and a $300k convertible note from a climate angel (6% interest, $8M cap, 20% discount). The note converts with its interest at the seed. The 20% discount gives a lower price than the $8M cap, so the angel gets about 457k shares. The founders together go from about 89% to 62% after the seed and 47% after a $9M Series A.
What the founders would tell you
- In hardware, model inventory and payment terms before anything else.
- Separate device margin from subscription revenue; show both growing.
- Read the stress test even when the Health Score is perfect.
- Use debt after equity, when repayments are clearly covered.
Not covered on this page
The full case also covers the Health Score review, the downside plan, the financial slides they built, the investor questions they rehearsed and their monthly routine after closing.