Microwave for RV oven power draw – it’s more than many users think

by | Jun 10, 2020 | Articles, CBRV, CME, Travel

by Collyn Rivers

Microwave oven power draw

Microwave for RV power draw is far greater than many users think. In this article, RV Books’ Collyn Rivers explains why – and how. This is a particular problem in caravans and motorhomes. Their deep-cycle lead-acid batteries cannot sustain the energy draw they require. AGM and lithium batteries are thus better suited.

A typical caravan or motorhome’s microwave oven is rated at 800 watts, but in terms of heat produced, not power draw). As most are only 50% efficient, that 800-watt microwave oven’s power draw is about 1200 watts.

Inverter loss

Microwave for RV power draw is also increased by losses within the inverter used to drive it. Inverters vary in efficiency. Some old ones are only 75% efficient, and thus best taken to the tip. The better current ones are 85%-90% efficient. Because of inverter losses, total microwave oven draw may thus be 1330 to 1600 watts. If run from 12 volts that’s 110-133 amps.
microwave for rv - dometic web

This 850 watt Dometic microwave oven draws about 1350 watts. Pic: Dometic

The amount of energy a microwave oven uses is proportional to its heat setting, and also to time. If run for 15 minutes at full heat, a 12 volt (800 watts) such oven will, via an inverter, draw 25 to 33 amp-hours. This may not seem much if you have a 150 amp-hour lead-acid battery, but it cannot do so for long. When high current is drawn, battery voltage consequently falls. It may fall too low to sustain that load. That may happen even with a battery still that’s still well charged. It may recover after resting but will not accept such high draw for long. The battery’s remaining capacity, however, is still there. It can readily be accessed used – but at a lower current draw.

Battery type and size

To power a microwave for RV, you really need at least a 250 amp-hour (12 volts) preferably AGM battery. Or about 100 amp hour of lithium (LiFePO4) batteries. It can be done from 150 – 200 amp hour deep cycle lead-acid batteries, but not for long at a time. Such high draw also shortens lead-acid battery life.

Ideally, confine extensive caravan and motorhome microwave use to the grid or generator power.

Every aspect of electrics in RVs is covered in Caravan & Motorhome Electrics. That on solar in RVs is in Solar That Really Works. Solar Success is for home and property systems. Caravan & Motorhome Book covers every aspect of RV usage. The Camper Trailer Book provides in-depth coverage of that area.

Collyn Rivers is a semi-retired automobile research engineer.  He is the author of seven books, five of which are about making RVs and solar work optimally.

Caravan and Motorhome Electrics

The essential handbook for anyone with an RV of any kind.  Everything you need to know to make the electrics in your rig work for you.

Cover of Caravan and Motorhome Books by Collyn Rivers

eBook versions

Paperback version

The book retailers set their own prices which can vary substantially. We'll aim to keep a selection of the better prices above.

Any bookshop, whether online or bricks and mortar, can order copies of Caravan & Motorhome Electrics.  Just ask.
ISBN: 978-0-6483190-8-5

Solar Success

Whether you’re building a new home or adding solar to an existing structure, this is the one book you can’t afford to be without.

eBook versions

Paperback version

Any bookshop, whether online or bricks and mortar, can order copies of Solar Success.  Just ask.
ISBN: 978-0-6487945-4-7

Why Caravans Roll Over
and how to prevent it

Explains in detail every aspect of tow vehicle and caravan stability. This is what you need to know to be safe on or off the road.

eBook versions

Paperback version

The book retailers set their own prices which can vary substantially. We'll aim to keep a selection of the better prices above.

Any bookshop, whether online or bricks and mortar, can order copies of Why Caravans Roll Over.  Just ask.
ISBN: 978-0-6483190-6-1

Solar That Really Works!

Solar that Really Works! covers the design, installation and use of solar in cabins, camper trailers, caravans, fifth wheelers, campervans and motor homes.

eBook versions

Paperback version

The book retailers set their own prices which can vary substantially. We'll aim to keep a selection of the better prices above.

Any bookshop, whether online or bricks and mortar, can order copies of Solar That Really Works!  Just ask.
ISBN: 978-0-6483190-3-0

The Caravan & Motorhome Book

The Caravan & Motorhome Book covers every conceivable aspect of campervan and motorhome usage. If you own a camper van or motor home, you'll want this book.

eBook versions

Paperback version

The book retailers set their own prices which can vary substantially. We'll aim to keep a selection of the better prices above.

Any bookshop, whether online or bricks and mortar, can order copies of The Caravan & Motorhome Book. Just ask.
ISBN: 978-0-6483190-5-4.

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Caravan and Motorhome Electrics

The essential handbook for anyone with an RV of any kind.  Everything you need to know to make the electrics in your rig work for you.

Cover of Caravan and Motorhome Books by Collyn Rivers

eBook versions

Paperback version

The book retailers set their own prices which can vary substantially. We'll aim to keep a selection of the better prices above.

Any bookshop, whether online or bricks and mortar, can order copies of Caravan & Motorhome Electrics.  Just ask.
ISBN: 978-0-6483190-8-5

Solar Success

Whether you’re building a new home or adding solar to an existing structure, this is the one book you can’t afford to be without.

eBook versions

Paperback version

Any bookshop, whether online or bricks and mortar, can order copies of Solar Success.  Just ask.
ISBN: 978-0-6487945-4-7

The Caravan & Motorhome Book

The Caravan & Motorhome Book covers every conceivable aspect of campervan and motorhome usage. If you own a camper van or motor home, you'll want this book.

eBook versions

Paperback version

The book retailers set their own prices which can vary substantially. We'll aim to keep a selection of the better prices above.

Any bookshop, whether online or bricks and mortar, can order copies of The Caravan & Motorhome Book. Just ask.
ISBN: 978-0-6483190-5-4.

Solar That Really Works!

Solar that Really Works! covers the design, installation and use of solar in cabins, camper trailers, caravans, fifth wheelers, campervans and motor homes.

eBook versions

Paperback version

The book retailers set their own prices which can vary substantially. We'll aim to keep a selection of the better prices above.

Any bookshop, whether online or bricks and mortar, can order copies of Solar That Really Works!  Just ask.
ISBN: 978-0-6483190-3-0

Why Caravans Roll Over
and how to prevent it

Explains in detail every aspect of tow vehicle and caravan stability. This is what you need to know to be safe on or off the road.

eBook versions

Paperback version

The book retailers set their own prices which can vary substantially. We'll aim to keep a selection of the better prices above.

Any bookshop, whether online or bricks and mortar, can order copies of Why Caravans Roll Over.  Just ask.
ISBN: 978-0-6483190-6-1