Additional

Battery backup or a generator?

One of these has killed at least 1,332 people since 2004. The other cannot start your well pump. Both facts belong in the decision.

Updated September 2026 · Data as of Federal rulemaking documents and manufacturer data sheets read on 3 September 2026

Written by HyreSolar Research team Research and analysis

Audited by HyreSolar Research team Data audit and fact check

1,332 generator CO deaths recorded, 2004 to 2021 And the regulator says it will rise

None of the manufacturers publish a battery run time So neither do we

4× difference between published surge ratings 185 LRA against 48 LRA

The short answer

The honest comparison is not about cost, it is about a safety record on one side and a capability limit on the other. Federal safety data attributes at least 1,332 carbon monoxide deaths to portable generators between 2004 and 2021, averaging 85 a year across 2017 to 2019, plus at least 23,318 emergency-department-treated injuries. Generators produce carbon monoxide at rates the regulator describes as "hundreds of times" a car's, and there is still no final federal standard requiring a shutoff. On the battery side the limit is different and less dangerous: no manufacturer publishes a run time, and what actually excludes loads is not stored energy but surge capability, where published figures differ by roughly fourfold between products and one manufacturer publishes none at all.

Read this part even if you read nothing else

Never run a generator inside an attached garage, including with the door open. This is not general caution, it is the specific finding of federal testing.

Two generators equipped with carbon monoxide shutoff features were run in an attached garage with the bay door fully open. Neither triggered its own shutoff. Both produced carbon monoxide concentrations in the living space that would have injured occupants, reaching carboxyhaemoglobin levels of 27 to 37% over a 329-minute test.

The safety feature did not save the occupants of that test house, and the open door did not either.

Follow the placement instructions in your generator's own manual. We are not giving you a distance figure, because the one that circulates everywhere does not appear in the federal document we read, and we could not verify it from the regulator directly.

The generator safety record, from the federal regulator

Comparisons of backup options usually treat safety as a footnote about ventilation. The federal data does not support treating it that way.

Deaths. The Consumer Product Safety Commission's rulemaking record attributes at least 1,332 carbon monoxide deaths to portable generators between 2004 and 2021, with an average of 85 deaths a year across 2017 to 2019.

Injuries. At least 23,318 emergency-department-treated carbon monoxide injuries over the same kind of period.

And the counts are understated by the reporting lag. The Commission notes its figures rise as reporting completes: one year's count for 2020 moved from 54 to 103 in a single year of subsequent reporting. So the numbers above are floors.

Why generators specifically. The regulator describes portable generators as producing carbon monoxide at rates "hundreds of times" that of a car. This is not a marginal difference in degree.

And there is still no final federal standard. The rulemaking we read is a proposed rule, and a search of subsequent federal publications found no final rule. Consumers currently buy against two voluntary industry standards, which the Commission itself found were not equally effective.

None of this makes generators unusable. Millions operate safely every year, outdoors, away from openings, following their instructions. It does mean that a comparison presenting a generator and a battery as two similar products differing on price has left out the most consequential difference between them.

The battery limit is surge, not stored energy

Batteries are compared on capacity in kilowatt-hours, which answers "how long" and not "what at all". The binding constraint on a home battery is usually the second question.

Motors draw far more current starting than running. A well pump, an air conditioning compressor, a large freezer: each demands a brief surge, measured as locked rotor amps, that dwarfs its running load. If the battery cannot supply that surge, the appliance does not start, no matter how much energy is in the pack.

The published figures differ enormously, and one manufacturer does not publish one. One product states a "Load Start Capability" of 185 LRA. Another states "up to 48 A LRA", with the manufacturer's own footnote that "Power Start capability may vary". A third publishes no surge figure at all in the documents we obtained.

That is roughly a fourfold spread on the specification that determines whether your well pump runs. It is also the specification least likely to appear in a sales conversation.

And where peak output is published, it is time-bounded. One manufacturer specifies 7.68 kVA peak with 32 amps for 3 seconds or 25.6 amps for 10 seconds. Those are different promises from a continuous rating and they are the ones a starting motor tests.

The question to ask is therefore specific: not "will this back up my house" but "what is the locked rotor amperage of my well pump and my air conditioner, and what surge does this product publish?" An installer who cannot answer that has not sized the system against your loads.

The 200-amp number on the sheet is not the continuous rating

A detail worth knowing before comparing backup controllers, because two manufacturers do the same thing.

Both rate their backup controller at 160 amps continuous, while the sheet also carries 200 amps. The 200 is the busbar and overcurrent protection rating, not what the unit will pass continuously.

That is not a discrepancy or a trick, it is two different specifications with two different meanings. But a comparison that reads 200 amps off one sheet and 160 off another is comparing different quantities, and the number that governs what your house can draw during an outage is the continuous one.

Nobody publishes a run time, and here is the only honest framing

The question everyone asks is how long a battery lasts in an outage. No manufacturer we read publishes an answer, and the reason is legitimate rather than evasive: it depends entirely on what you run.

The only defensible calculation from published specifications is usable capacity divided by the product's own maximum continuous power. Do that across the products we examined and every one lands at roughly 1.2 to 1.3 hours.

That is not a run time and it should not be read as one. It is the shortest possible answer: how long the battery lasts if you draw the maximum it can deliver, continuously, from full. Nobody's house does that.

What it is useful for is the ceiling. If you were hoping a single battery would carry a normal household through a multi-day outage, that arithmetic tells you it will not, and no amount of load management changes the order of magnitude.

The realistic version is that a battery carries a reduced set of loads for a much longer period, and how long depends on which loads, which is why a credible proposal starts from your list rather than from a product's capacity. If solar is charging it during the day, the picture changes again, favourably, and only in daylight.

Read what "whole-home backup" means in the document

The phrase is used loosely and the manufacturers are more careful than the marketing.

One manufacturer's installation guide forbids whole-home backup outright for one of its configurations. Not discourages: forbids, in the install guide.

Another manufacturer's "whole-home backup" still excludes what it calls Smart Circuits, which are the large 240-volt loads specifically designed to shed first.

So in at least one case, "whole home" means the whole home minus the things that use the most power. That may be exactly what you want, and it is not what the phrase implies.

Ask which specific circuits will be backed up, get the list in writing, and check it against the appliances you actually care about during an outage.

The comparison, on the dimensions that actually differ

	Home battery	Portable generator
Carbon monoxide risk	None	At least 1,332 deaths 2004 to 2021, and no final federal standard
Runs indoors	Yes, subject to code and manufacturer restrictions	Never, including an attached garage with the door open
Duration	Limited by stored energy. No manufacturer publishes a run time	Limited by fuel, which can be replenished
Starting large motors	Limited by published surge, which varies fourfold between products	Generally stronger, and the reason many people keep one
Automatic operation	Yes, the transfer switch is typically inside the controller	Manual for portable units; automatic for standby installations
Refuelling during an outage	Not applicable; recharges from solar in daylight	Requires fuel to be available and stored
Noise	Silent	Audible, and subject to local ordinances
Maintenance	Minimal	Regular running, oil, fuel stabilisation

Safety figures from the federal rulemaking record; battery figures from manufacturer data sheets and installation guides. Read 3 September 2026.

The two bold rows are the real trade. A generator will start things a battery may not and can run as long as you have fuel. A battery cannot poison you. Those are different kinds of consideration and the second is not a footnote.

How to decide, given all this

1
Write down what actually has to run
Not "the house". A refrigerator, some lights, a router, a medical device, a well pump, a furnace fan. That list is the specification, and everything else follows from it.
2
Find the locked rotor amperage of anything with a motor
It is on the appliance nameplate. Well pumps and air conditioning compressors are the usual problems, and this is the number that determines whether a battery can start them at all.
3
Ask for the product’s published surge figure, and its time limit
One product publishes 185 LRA, another up to 48 with a caveat that it may vary, and a third publishes nothing. Where a peak is given with seconds attached, that time bound is part of the specification.
4
Ask which circuits are backed up, in writing
Because "whole-home backup" demonstrably does not always mean the whole home. One manufacturer forbids it outright for a configuration and another excludes its largest loads by design.
5
If you keep a generator, treat placement as the safety decision it is
Follow its own manual. Never in an attached garage, including with the door open, because federal testing showed shutoff-equipped units failing to trigger in exactly that scenario while producing injurious indoor levels.
6
Fit carbon monoxide alarms regardless
This is the cheapest item in the entire comparison and the one with the clearest evidence behind it. If a generator is anywhere in your plan, working alarms on every level are not optional.
7
Consider that the answer may be both
A battery for silent, automatic, frequent short outages, and a generator kept for the rare multi-day event, is a coherent arrangement. The comparison is often framed as exclusive when the failure modes are complementary.

Method and limitations

What was read

The Consumer Product Safety Commission's supplemental notice of proposed rulemaking on a safety standard for portable generators, read as the published federal document, for the death and injury figures, the reporting-lag observation, the comparison of emission rates, the status of the rulemaking and the assessment of the voluntary standards.

The federal testing described in that record, in which shutoff-equipped generators run in an attached garage with the door open failed to trigger while producing injurious indoor carbon monoxide.

Manufacturer data sheets and installation guides for the surge ratings, the continuous versus busbar controller ratings, the peak output time bounds, the usable capacity figures and the backup configuration restrictions.

The number we deliberately do not give you

A generator placement distance. A specific figure circulates on nearly every page about this and we could not verify it. It does not appear in the federal document we read, and the regulator's own site refused every request from our environment.

So follow your generator's manual, which is authoritative for that product. What we can state from the record, because it was tested, is that an attached garage with the door open is not safe.

What we could not obtain

Electrical code article text on optional standby and stand-alone systems is paywalled and was not read. Where this page describes what equipment does, it draws on manufacturer installation guides, which state what the manufacturer requires rather than what the code does.

No generator run time, fuel consumption or maintenance data from a primary source, and no local noise ordinance survey. Those rows in the table are qualitative and are presented as such.

And no cost comparison at all. Installed costs for both depend on your panel, your loads and your house, and no source we read supports a general figure.

On the safety material specifically

We have been deliberately conservative with it. Every figure is attributed to the federal rulemaking record, described as a floor where the regulator says reporting is incomplete, and we have not extrapolated, annualised or projected any of it.

Carbon monoxide kills people quickly and without warning, and this is not a subject for approximation. If any part of your plan involves a generator, the relevant authority is its manual and your local building department, not this page.

Questions

Is a battery safer than a generator?

On carbon monoxide, unambiguously. Federal data attributes at least 1,332 CO deaths to portable generators between 2004 and 2021, averaging 85 a year across 2017 to 2019, plus at least 23,318 emergency-department-treated injuries, and there is still no final federal standard requiring a shutoff. A battery produces no combustion products at all.

Is it safe to run a generator in the garage with the door open?

No, and this is tested rather than assumed. Federal testing ran two generators equipped with carbon monoxide shutoff features in an attached garage with the bay door fully open. Neither triggered its own shutoff, and both produced living-space concentrations that would have injured occupants, reaching carboxyhaemoglobin levels of 27 to 37% over a 329-minute test.

How long will a home battery last in an outage?

No manufacturer publishes an answer, because it depends entirely on what you run. The only calculation the published specifications support is usable capacity divided by the product’s own maximum continuous power, which lands at roughly 1.2 to 1.3 hours across the products we examined. That is a floor rather than a run time: it assumes you draw the maximum continuously.

Can a battery run my air conditioning or well pump?

That depends on surge rather than on capacity, and the published figures vary enormously. One product states a load start capability of 185 locked rotor amps, another states up to 48 with the manufacturer’s own caveat that it may vary, and a third publishes no surge figure at all. Find the locked rotor amperage on your appliance nameplate and ask for the product’s published surge against it.

What does "whole-home backup" actually mean?

Less than it says, in at least two cases we read. One manufacturer’s installation guide forbids whole-home backup outright for one configuration. Another’s whole-home backup still excludes the large 240-volt loads it designates as sheddable. Ask which specific circuits are backed up and get the list in writing.

Why does the spec sheet say 200 amps if the controller is 160?

Because they are different specifications. The 200 amps is the busbar and overcurrent protection rating; the 160 amps is what the unit passes continuously. Both appear on the same sheet legitimately, and the continuous figure is the one that governs what your house can draw during an outage.

How far from the house should a generator be?

We are not going to give you a distance, because the figure that circulates everywhere does not appear in the federal document we read and we could not verify it from the regulator. Follow the placement instructions in your generator’s own manual, which is authoritative for that product, and never operate it in an attached garage even with the door open.

Should I get both?

It is a coherent answer and the comparison is often framed as though it is not. A battery handles frequent short outages silently and automatically; a generator handles the rare multi-day event and starts loads a battery may not. The failure modes are complementary, and the main reason to choose one is budget rather than logic.

Written and audited by

HyreSolar Research

Primary-source research, data analysis and fact checking

We are a research desk, not a sales floor. We read the statute, the tariff, the code section, the federal filing or the manufacturer data sheet ourselves, and we publish the figure with the document it came from and the date we retrieved it. Where a number cannot be traced to a primary source, we publish the shorter page and say what we could not verify. That rule has cost us whole sections, and it is the reason the rest can be trusted.

160: primary sources read and cited
220: figures with a retrieval date
115: federal and state government sources
66: researched pages published

How this desk works

Primary sources only. Statutes from the legislature’s own publishing system, federal data from the agency that collects it, code text from the adopted edition, manufacturer claims from the data sheet. We do not cite an article that cites a source; we go and read the source.
Every figure carries its provenance. A named document and the date we retrieved it, so you can check it and so you know how old it is. Retrieval dates are not decoration: an EIA rate from May is a different fact from an EIA rate from August.
We publish what we could not verify. Every research page carries a section naming the things we tried to establish and could not, and why. A paywalled standard, a state website that refused the request, a manufacturer that publishes no figure at all.
We separate measurement from modelling from our own reasoning, and label which is which on the page. A laboratory measurement, an assumption inside a modelling tool and our own inference are three different kinds of claim and they are never presented as one.
We do not sell solar, and we take no payment for placement, ranking or a favourable mention. Nobody buys a position on this site.

Data as of Federal rulemaking documents and manufacturer data sheets read on 3 September 2026. Authorship on this site is organisational: the analysis belongs to the desk rather than to a named individual, and we do not publish credentials we do not hold. Our editorial policy sets out how we source, date and correct what we publish.

Sources & retrieval dates

US Consumer Product Safety Commission, Safety Standard for Portable Generators, 88 FR 24346 — Supplemental notice of proposed rulemaking, published 20 April 2023, read as the published federal document. Source for at least 1,332 carbon monoxide deaths associated with portable generators between 2004 and 2021, the average of 85 deaths a year across 2017 to 2019, at least 23,318 emergency-department-treated injuries, the observation that counts rise as reporting completes with one year’s 2020 figure moving from 54 to 103, the description of emission rates as hundreds of times those of a car, the assessment of the voluntary standards as unequally effective, and the federal testing in which shutoff-equipped generators in an attached garage with the door open failed to trigger while producing carboxyhaemoglobin levels of 27 to 37% over a 329-minute test. Verified as a proposed rule: a subsequent search of federal publications found no final rule. Retrieved 3 September 2026.
Enphase IQ Battery 5P data sheet and IQ System Controller 3 Quick Install Guide — Source for the stated surge capability of up to 48 locked rotor amps with the manufacturer’s footnote that power start capability may vary, the time-bounded peak output of 7.68 kVA at 32 amps for 3 seconds or 25.6 amps for 10 seconds, the 160 amp continuous controller rating against the 200 amp busbar and overcurrent protection rating, the integration of the transfer switch and microgrid interconnection device within the controller, and the prohibition on whole-home backup for one configuration. Retrieved 3 September 2026.
Tesla Powerwall 3 Datasheet — Source for the stated load start capability of 185 locked rotor amps and the usable capacity figure used in the maximum-draw calculation. Retrieved 3 September 2026.
FranklinWH installation guide and system user manual — Source for the 160 amp continuous controller rating, for the verified absence of any published surge figure in the documents obtained, and for the finding that its whole-home backup configuration still excludes the circuits it designates as sheddable. Retrieved 3 September 2026.

Working out what you actually need backed up?

Send us the list of loads and the appliance nameplates. We will tell you what surge they need, what the products publish, and whether the answer is a battery, a generator or both.

Size a backup system Open the calculators

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