Hybrid vs off-grid solar systems for business
In short
For most businesses, a grid-connected hybrid system — PV plus battery, utility as the fallback — is the right topology: it handles outages and peak pricing without making the battery carry the whole site. True off-grid only makes sense when there is no utility supply or the grid is effectively dead, and it costs more because the battery must cover the longest sunless stretch, not just the outage gap.
The short answer
Choose by answering one question: what happens when the grid fails, and for how long? If outages are short or tolerable, grid-tied PV without storage is cheapest. If outages are frequent but bounded, hybrid (PV + battery + grid) is the standard answer. If there is no grid — or it fails for days at a time — you are designing off-grid, and the generator, not the battery, usually becomes the long-duration reserve.
Configuration and comparison
| Dimension | Grid-tied (PV only) | Hybrid (PV + battery) | Off-grid |
|---|---|---|---|
| Grid dependency | Shuts down in an outage (anti-islanding) | Rides through short outages on battery | None |
| Battery dependency | None | Covers the outage gap and evening peak | Covers every night and every cloudy stretch |
| What sizes the battery | — | Critical load × outage duration | Critical load × longest sunless period |
| Typical battery size for the same site | None | Smallest of the three | Largest of the three — often 3–5× the hybrid design |
| Failure mode | Production stops with the grid | Battery drains to reserve, then generator or grid | Load shedding when reserves run low |
| Where it fits | Reliable grid, no outage cost | Unreliable grid or demand-charge tariff, bounded outages | No grid, or grid down for days; remote sites |
How to read this table: compare the two battery rows first. The battery is the expensive component in every topology, and what sizes it — outage gap versus longest sunless stretch — is the difference between a hybrid budget and an off-grid budget.
How this is decided, and what we assume
The decision needs three inputs, all site-specific:
- Outage frequency and duration distribution. Twelve months of outage logs, or the utility's published reliability figures. A site with 30 outages of 40 minutes designs very differently from one with 4 outages of 2 days.
- The critical load list. What must stay live, in kW. This is the same list that sizes the battery in the sizing method.
- Generator availability. An existing, serviced genset shortens the battery design window dramatically — the battery only needs to cover grid failure to generator start.
The common error runs the other direction: buying an off-grid design for a site with a usable grid. The battery gets sized for the worst sunless week, sits mostly idle the rest of the year, and the project never earns its capital back. The solar-diesel hybrid logic shows how a generator as reserve shrinks that battery back to an economic size.
Project evidence
Anonymised references for each topology — region, configuration, load profile and delivery status — are listed on the configuration page. Measured results are published wherever the customer has approved disclosure.
When each choice is wrong
- Off-grid is wrong when a working grid exists: the battery needed for sunless stretches costs multiples of the hybrid design and sits idle most of the time.
- Hybrid is wrong when the grid is reliable and the tariff has no demand component: the battery then has no job, and a grid-tied system delivers the same savings for less.
- Grid-tied without storage is wrong when an outage costs more per hour than the entire annual PV saving — which is the cold-storage failure mode described on the factory application page.
Next step
Send your outage history (even a rough log), the critical load list, and whether a generator exists on site. Those three items settle the topology question before any equipment is discussed.