Generator FAQ

It comes from what you want running rather than from the square footage. Most Marin homes land between 14kW and 26kW on an air-cooled unit, covering heating, refrigeration, lighting, outlets, the network and usually one air-conditioning zone. Essential-circuit systems start around 10kW to 14kW. Larger properties with pool equipment, a well pump, several HVAC zones or a guest house generally need a liquid-cooled set of 30kW or more. The figure that actually decides it is the starting surge of your biggest motor, not the running total.

A portable unit is stored in the garage, wheeled out, started by hand and refuelled every eight to twelve hours, producing roughly 3kW to 12kW on gasoline or propane through an inlet box and interlock. A standby set is permanently installed outside, runs on natural gas or propane, produces 10kW to 60kW or more, and starts itself within thirty seconds with nobody home. The practical dividing line is whether anyone will reliably be there to deploy it.

Natural gas where PG&E serves the street, because there is no tank to site, nothing to refill and no ceiling on run time. Propane past the last gas main, which covers parts of Fairfax, west Novato and the higher lots elsewhere; it stores indefinitely and burns clean, but a tank holds a finite number of hours so a multi-day event needs a refill plan. Diesel gives the most output per unit of size and the longest run under heavy load, which is why it dominates commercial and industrial work, and it rarely makes sense on a house.

We install Generac, Kohler, Cummins and Champion, and we service those plus Caterpillar and most other makes regardless of who supplied them. Generac has the widest parts availability in this county. Kohler is quieter in several of its residential sizes. Cummins suits the larger liquid-cooled and commercial sets. Being independent of any single brand is the point: the recommendation follows the property rather than our stock.

Typically $5,000 to $15,000 in Marin, covering the unit, the concrete pad, the automatic transfer switch, the electrical and gas connections, the permit and the commissioning. Essential-circuit systems sit at the lower end and large liquid-cooled sets on big properties run above it. A service panel upgrade, a propane tank or a long trench from the meter are the three things most likely to move a quote upward.

One to three days on site. A natural gas install on a straightforward property with an adequate panel is often a single day for a crew of two; propane, a panel upgrade or a hillside position takes two or three. The longer part of the calendar comes before we arrive, because permits typically take one to three weeks depending on the town and a PG&E meter upsize can take longer than that. We file both the week the job is signed.

Yes, in every Marin town. An electrical permit always, and usually a mechanical or plumbing permit for the gas connection. Tiburon, Belvedere, Ross and the Larkspur historic core add design review for anything visible from the street, and parcels in mapped flood zones in San Anselmo and the Corte Madera flats carry elevation requirements. We file the permits, prepare the siting drawing and attend the inspection as part of the price.

It is the device that makes a standby system automatic. It watches the utility supply, signals the generator to start when that supply fails, and physically isolates your building from the grid before connecting it to the generator. That isolation is a safety requirement rather than a refinement, because backfeeding a dead line can kill the utility crew repairing it. A whole-panel switch covers everything; an essential-circuits switch covers a selected subpanel and lets a smaller machine do more.

Manufacturers generally require at least 18 inches from the wall and five feet from any openable window, door or vent, with clearance above and in front for airflow and service access. Each town then enforces its own property line setback, and several have noise limits that push the unit further from a neighbour in practice. On a narrow canyon lot in Mill Valley or on the Sausalito hillside there is sometimes only one compliant position, which is why we measure at the survey.

Modern residential units run roughly 60 to 70 dB at seven metres, about the level of a normal conversation. The part neighbours notice is the weekly self-test rather than the outage itself, so we set that to a mid-morning weekday on the shortest cycle the controller allows. Where lots are tight, a liquid-cooled unit in an acoustic enclosure is meaningfully quieter under load and usually worth the difference.

By size tier and duration. A small portable up to about 10kW runs roughly $75 to $150 a day. A mid-sized towable set of 20kW to 60kW, which covers most weddings and small job sites, is about $200 to $500 a day or $1,200 to $3,000 a month. Larger machines from 100kW upward start around $600 a day and are normally quoted monthly. Delivery, collection and the distribution equipment are inside those numbers.

Weddings and events on properties with no usable supply, construction sites before the utility connection exists, film and production units on location, wineries during crush, facilities running through a planned shutdown or a switchgear upgrade, and anyone covering a long outage or a failed machine while a part is on order. If you find yourself hiring the same set every year, that is usually the point where buying costs less.

It is agreed in writing before delivery. Short hires and events are normally delivered full and returned full, with the tank sized so the machine runs the whole event without a mid-event refuel. Longer construction and industrial hires are refuelled by us on a schedule with the fuel billed as used. Either way the arrangement is in the quote rather than a surprise afterwards.

A residential standby set needs a full service once a year, or every 100 to 200 running hours, plus the weekly self-test it runs on its own. Commercial and industrial machines are typically twice a year with an annual load bank test. The interval is driven by time as much as hours, because oil degrades and batteries age whether or not the machine has run. A skipped service is the best single predictor of a failed start.

On natural gas, effectively as long as the outage lasts, with a break for an oil service on very long runs, because the fuel arrives by pipe. On propane it depends on tank size and load; a 500-gallon tank will typically carry a mid-sized standby set for two to five days. A portable on gasoline runs eight to twelve hours per tank. Diesel sets carry their own supply and are sized around a target run time, commonly 24 to 72 hours before refuelling.

Industry surveys generally put the effect at roughly 3 to 5 percent of home value, and in a county with repeated public safety shutoffs and multi-day storm outages it is a feature buyers here ask about directly. Treat it as a genuine improvement rather than a guaranteed return. The honest reason almost everyone buys is the outages, and any resale benefit is a bonus on top.

Manufacturer-backed financing is available on most residential standby installations, typically as fixed monthly payments over two to seven years subject to credit approval, and there are periodic promotional terms from the major brands. Commercial customers more often use equipment leasing or a capital purchase, and we can quote the installation either way. We will lay out the options with the total cost of each rather than only the monthly figure.

Fuel is the main running cost and it depends on load, because a set at half load burns far less than one at full. As a rough guide, a 22kW air-cooled unit on natural gas costs a few dollars an hour at typical household load, and propane runs meaningfully higher per hour than gas. On top of that, budget for the annual service, and a battery every three years or so. Over a decade the servicing usually costs less than a single long outage in a house full of food and a freezer.

It depends on what you want running rather than on the square footage. Most Marin homes land between 14kW and 26kW on an air-cooled unit, which covers heating, refrigeration, lighting, outlets, the network and usually one air-conditioning zone. Essential-circuit systems start around 10kW to 14kW. Larger properties with pool equipment, a well pump, several HVAC zones or a guest house generally need a liquid-cooled set of 30kW or more. We size it from your panel and the starting surge of the biggest motor, because that surge is what trips an undersized machine on the first real outage.

A complete installation in Marin typically runs $5,000 to $15,000 including the unit, the concrete pad, the automatic transfer switch, the electrical and gas connections, the permit and the commissioning. Smaller essential-circuit systems sit at the lower end. Large liquid-cooled units on big properties run above it. A service panel upgrade, a propane tank or a long trench from the meter are the three things most likely to move a quote upward.

The work on site is usually one to three days. A natural gas install on a straightforward property with an adequate panel is often a single day for a crew of two. Propane, a panel upgrade or a difficult hillside position takes two or three. The longer part of the calendar is before we arrive: permits typically take one to three weeks depending on the town, and a PG&E meter upsize can take longer than that, which is why we file both as soon as the job is signed.

Yes. Every town in Marin requires an electrical permit, and most require a mechanical or plumbing permit for the gas connection as well. Tiburon, Belvedere, Ross and the Larkspur historic core add design review for anything visible, and parcels in mapped flood zones in San Anselmo and Corte Madera carry elevation requirements. We file the permits, prepare the siting drawing and attend the inspection as part of the price.

It is the device that makes a standby system automatic. It monitors the utility supply, tells the generator to start when the supply fails, and physically disconnects your house from the grid before connecting it to the generator. That isolation is a safety requirement, because backfeeding a dead line can kill the utility crew repairing it. A whole-panel switch covers the entire house; an essential-circuits switch covers a selected subpanel and lets a smaller generator do more.

Manufacturers generally require at least 18 inches from the wall and five feet from any openable window, door or vent, with clearance above and in front for airflow and service access. On top of that, each Marin town enforces its own property line setback, and several have noise limits that effectively push the unit further from a neighbour. On a narrow canyon lot there is sometimes only one compliant position, so we measure it at the survey rather than assuming.

Modern residential units run roughly 60 to 70 dB measured at seven metres, comparable to a normal conversation or a dishwasher. The part neighbours actually notice is the weekly self-test rather than the outage, so we set that to a mid-morning weekday at the shortest cycle the controller allows. Where lots are tight, a liquid-cooled unit in an acoustic enclosure is meaningfully quieter under load and is worth the difference.

Natural gas is the easiest choice where PG&E serves the street, because there is no tank and no run-time limit. Propane suits properties past the gas main, stores indefinitely and burns clean, but a tank holds a finite number of hours so a multi-day outage needs a refill plan. Diesel gives the most power per unit of size and the longest run time under heavy load, which is why it dominates commercial and industrial work, but it needs fuel storage, periodic polishing and emissions consideration and rarely makes sense on a house.

Industry surveys generally put the effect at roughly 3 to 5 percent of home value, and in a county with repeated public safety shutoffs and multi-day storm outages it is also a feature buyers here ask about specifically. Treat it as a genuine improvement rather than a guaranteed return: the honest reason most people buy is the outages themselves, and the resale effect is a bonus rather than the case for it.

A portable unit is a machine you store, wheel out, start by hand and refuel every eight to twelve hours, typically producing 3kW to 12kW on gasoline or propane and connecting through an inlet box and interlock. A standby set is permanently installed outside, runs on natural gas or propane, produces 10kW to 60kW or more, and starts itself within thirty seconds of an outage with nobody home. The practical dividing line is whether anyone will reliably be there to deploy it.

For a couple of appliances, yes, provided the cords are rated for it and the generator is outside and well clear of any window or vent, because carbon monoxide from a machine run in a garage or under a deck kills people every winter. What you must never do is plug a generator into a wall or dryer outlet to feed the panel. That backfeeds the utility line and can electrocute the crew repairing it. A proper inlet and interlock costs a fraction of what most people expect.

A permanently installed unit on natural gas can run for days on end, effectively as long as the outage lasts, with a break for an oil service on very long runs. On propane, run time comes down to tank size: a 500-gallon tank will typically carry a mid-sized standby set for two to five days depending on load. A portable on gasoline runs eight to twelve hours per tank, which means refuelling twice a day and keeping fuel stored safely.

It can, if it is sized for it and your electrical service will take a whole-panel transfer switch. Many people are better served by an essential-circuits design covering heating, refrigeration, water, network and lighting, because it needs a much smaller machine for a much smaller price. The item that most often forces the size upward is air conditioning, followed by a well pump and pool equipment.

Any generator connected to your house wiring does, whether that is an automatic transfer switch or a manual one or a listed interlock kit at the panel. It is what guarantees the generator and the utility supply can never be live at the same time. It is required by code, it is inspected, and it is the part that keeps a line worker alive.

They solve different halves of the problem. A battery is silent, needs no fuel and typically carries a house for a few hours to a day. A generator is noisy and needs fuel but will run for as long as the outage lasts. In a county that regularly sees multi-day storm and shutoff events, plenty of households end up with both, configured so the battery carries the load quietly and the generator recharges it.

Once a year for a residential standby set, or every 100 to 200 running hours if it has done a lot of work, plus the weekly self-test which happens on its own. Portable units need the oil changed every 50 to 100 hours and the fuel stabilised or drained if they are going to sit. Skipping the annual visit is the reason most generators that fail during an outage fail.

From a load study rather than a nameplate total. We look at the critical load schedule, the motor starting characteristics, any non-linear loads such as variable speed drives and UPS systems, and where the picture is unclear we meter the site over a working week to capture real peaks. Nameplate arithmetic almost always produces a machine that is both too large and wrong, because it captures neither the diversity of the real load nor the surge behaviour that actually sets the requirement.

Diesel gives the most output for a given physical size, accepts large block loads without stalling, and carries its own fuel so the machine does not depend on a gas network that may be affected by the same event. That independence is the point of a standby set. Gas machines do appear at industrial scale where emissions rules, fuel logistics or run-hour patterns favour them, but diesel is the default above about 150kW.

A load bank applies a controlled resistive load so the set can be run at or near its rated output without the facility being involved. It proves the machine under real conditions, which a monthly light-load exercise run does not, and it burns off the unburnt fuel and carbon that light running deposits in the cylinders and exhaust. Some occupancies are required to load bank test annually; for everyone else it is the difference between believing the generator works and knowing it does.

Typically a minor service every six months or 250 running hours and a major service annually, alongside weekly or monthly automatic exercise runs and an annual load bank test. Fuel needs sampling and polishing on a schedule of its own, batteries are the single most common failure item and are replaced on age rather than on test, and coolant needs analysis rather than a glance at the header tank.

Stationary diesel engines in the Bay Area require registration or permitting, with conditions on engine emissions tier, aftertreatment and the number of hours the machine may run annually for testing and maintenance. Running during an actual utility outage is treated separately from routine testing. We handle the application as part of the project and set the testing regime so it stays inside the permitted hours.

Mostly, yes. New installations on a site with no existing standby capacity are done live with only the final tie-in needing a window. Replacing an existing set is more involved, and we usually bring in a temporary rental unit to hold the standby duty while the changeover happens, so the facility is never actually without cover.

We assess it honestly. Controls obsolescence and parts availability tend to decide it before the engine does, and a set that has spent twenty years running light monthly tests is often wet-stacked and down on output. Sometimes the right answer is a controls retrofit and a proper load bank regime; sometimes the next major repair costs more than a replacement. We will tell you which, with the test data behind it.

It depends on which loads you decide are essential and how they start rather than on the size of the building. A restaurant might need 30kW to 60kW to carry refrigeration, ventilation, lighting and point of sale. A medical suite with imaging equipment can need more than a much larger office. Where the profile is unclear we fit recording meters for a week, because three-phase motor starting and step loading set the requirement more than total kilowatts do.

A small three-phase system for a restaurant, clinic or retail unit generally runs $15,000 to $30,000 installed. Mid-sized office and light industrial systems commonly land between $30,000 and $80,000. The machine itself is usually less than half of that once the transfer equipment, the civil work, the fuel system, the permits and the commissioning are included, which is why a quote given over the phone is not worth much.

Twice a year as a rule, plus an annual full-load test and the automatic weekly or monthly exercise run the controller does on its own. A typical agreement covers oil and filters, fuel filters and sampling, coolant analysis, a battery test with replacement on age rather than on failure, a transfer switch exercise and a written report. Batteries and degraded fuel cause the large majority of failed starts, and both are schedule items.

It depends on the occupancy. Healthcare, high-rise buildings, certain assembly occupancies and buildings with specific life safety systems carry requirements for emergency or legally required standby power, with prescribed testing intervals and record keeping. Most ordinary offices, shops and restaurants have no obligation and install standby power for commercial reasons. We will tell you which category you are in before you spend anything.

Nearly all of it, yes. The pad, the machine, the conduit and the cabling go in while you trade. Only the final tie-in and the transfer switch cut-over need the supply down, and for restaurants, clinics and retail we schedule that overnight or on a closed day. We agree that window before the job starts rather than negotiating it on the day.

Yes, and a good share of our contract base came to us that way. We service Generac, Kohler, Cummins, Caterpillar and the other major brands regardless of who supplied them. The first visit on an inherited machine is a full assessment: load test, fuel sample, battery test, controller check and a written report on what it needs, before any schedule is agreed.

Call us. We carry common filters, batteries, belts and controller spares for the machines we maintain, and contract customers have a defined response time rather than a place in the general queue. Where the fault cannot be fixed on the visit and the building cannot trade without power, we can put a rental set in place while the repair is completed.

A residential standby unit needs a full service once a year, or every 100 to 200 running hours if it has done unusual work, plus the weekly self-test it runs on its own. Commercial and industrial sets are typically twice a year with an annual load test. The interval is driven by time as much as by hours, because oil degrades and batteries age whether or not the machine has run.

An oil and filter change, air filter, spark plugs on a gas machine, a battery capacity test under load, coolant check or analysis on liquid-cooled units, fuel filter and fuel condition check on diesel sets, valve clearance at the longer intervals, an inspection of the enclosure for rodent damage, a controller and fault log review, and a transfer test with the machine under load. You get a written report afterwards.

The battery, most of the time. Standby batteries fail from age and from sitting rather than from use, and a voltmeter reading of 12.6 volts tells you very little about whether it will turn an engine. After that, in rough order: stale or contaminated fuel, a blocked fuel filter, a failed battery charger, a fuel solenoid, and then the genuinely expensive items. A diagnostic visit sorts most of it in an hour.

Yes, and most of our service base arrived that way. We work on Generac, Kohler, Cummins, Caterpillar, Champion and the rest, including machines whose original installer is no longer trading. The first visit on an unfamiliar set is a full assessment with a written report, so any repair decision is made on evidence rather than on a hunch.

Annually on a residential standby set, or every 100 to 200 running hours, whichever comes first. Larger liquid-cooled and diesel machines run to a shorter hours-based interval, commonly 250 hours. Portable units need it every 50 to 100 hours. The reason time matters as much as hours is condensation and additive breakdown in an engine that spends most of its life cold.

Yes, out of hours and at weekends, dispatched from our San Rafael shop across all ten towns we cover. Customers on a maintenance agreement have a defined response time. We carry the batteries, filters, belts and common sensors that account for most no-start faults, so the majority of emergency visits end with the machine running rather than with a parts order.

A well-maintained residential air-cooled unit typically gives fifteen to twenty-five years, and a liquid-cooled or industrial diesel set can run far longer than that on hours alone. What usually ends a machine’s life is controls obsolescence and parts availability rather than a worn engine. A set that has been serviced annually is generally worth repairing; one that has sat untouched for a decade often is not.

On a diesel set, persistent white or blue smoke with unburnt fuel in the exhaust is usually wet stacking, caused by years of running short monthly tests at almost no load so the engine never reaches temperature. It is reversible with a load bank test to burn off the deposits, but it comes straight back unless the exercise regime is changed to load the machine properly.

It is priced by size tier and duration. A small portable unit up to about 10kW runs roughly $75 to $150 a day. A mid-sized towable set of 20kW to 60kW, which suits most weddings and small job sites, is about $200 to $500 a day, or $1,200 to $3,000 on a monthly rate. Larger machines from 100kW upward start around $600 a day and are normally quoted by the month. Delivery, collection and the distribution equipment are inside those numbers.

Most Marin ranch and vineyard weddings land between 20kW and 60kW once catering, lighting, a bar, sound and a photographer are added together. The kitchen is almost always the largest and most underestimated load, so we size these with the caterer rather than from a guest count. Noise matters as much as capacity, so event bookings go out on quiet enclosed units rather than standard construction sets.

It is agreed in writing before delivery and there are two normal arrangements. Short hires and events are usually delivered full and returned full, with the tank sized so the machine will run the whole event without a mid-event refuel. Longer construction and industrial hires are refuelled by us on a schedule and the fuel is billed as used. Either way it is in the quote rather than a surprise on the invoice.

From a single day up to as long as the job runs, and plenty of our construction hires go on for a year. Anything past a couple of weeks should be on a monthly rate rather than stacked weekly ones, because the delivery and collection are the same work whether the machine stays a week or a season and monthly pricing spreads that over more days.

Yes. We deliver, position the set, connect the distribution and test it under load before leaving, then collect it when you are finished. Delivery and collection are inside the quoted price for anywhere in the ten towns we cover. On events we also make sure somebody on site knows how to reset a tripped breaker, because that is the call that otherwise comes at nine in the evening.

The enclosed units we send to event work are, and the standard construction sets are not, which is why we do not send those to weddings. Beyond the machine itself, siting does most of the work: putting the set behind a structure, away from the marquee and downwind of the seating makes a bigger difference than the last few decibels on a spec sheet.

Always, and it comes with the machine rather than as an extra. Distribution boards, cable in the right lengths, correct connectors, RCD protection and cable ramps where people walk are what make the output usable. A generator delivered without the right connector is the single most common way a hire goes wrong.